a monthly newsletter of environmental science and policygreen urbanism: learning from european...

Environmental ReviewA Monthly Newsletter of Environmental Science and Policy

Volume Seven Number Two February 2000

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Introduction:

Urban sprawl is a growingproblem for many American cities.Poorly planned development results intraffic congestion and gridlock, loss offarmland and wildlife habitat, waterquality and flood control problems,and increased taxes. In his book,Green Urbanism1, Timothy Beatleydescribes a wide range of innovativebuilding and planning ideas fromseveral European cities and discusseshow they may be adapted to Americancities. As the book shows, there aremany ways we can reduce sprawl andin the process save money and taxesand improve our quality of life.

ER:ER:ER:ER:ER: Professor Beatley, what is yourtraining?

TB:TB:TB:TB:TB: My Ph.D. and Master’s degreesare in planning. In addition I also havea Master’s degree in political science,which is an acknowledgment thatplanning is an inherently politicalactivity. I teach within the Departmentof Urban and Environmental Planningin the School of Architecture at theUniversity of Virginia. I’ve been herethirteen years teaching a variety ofenvironmental policy and planningclasses. We’re a bit of a uniqueprogram in that we have a strongemphasis on environment and envi-ronmental planning.

ER:ER:ER:ER:ER: Why did you decide to write abook?

TB:TB:TB:TB:TB: The book Green Urbanism is anextension of many things that I’vebeen working on the last few years.I’ve had a particular interest in howsustainability relates to cities, towns,human settlement patterns and places.Sustainability is often used as anadjective, sustainable forestry, sustain-able fisheries. My interest has been inapplying that notion to the builtenvironment — to the cities and townswhere we live — thinking about whata sustainable city or a sustainablecommunity is or could be. This bookis in a sense, a merging of the environ-

mental agenda with the urban or cityplanning agenda.

The book comes out of anextended period of living and workingin Europe. The project began aboutthree years ago when I spent a yearliving and teaching in the Netherlands.I had a small grant from the LincolnInstitute of Land Policy, a Cambridge,Massachusetts, think tank focused onland planning and urban policy, toidentify a small number of Europeancities that were doing exemplary,cutting-edge work in the sustainabilityarea. As I began to get into the work ittook on a much larger scale and scope;instead of a handful of cities I endedup looking at about twenty-five citiesin eleven countries.

My overall goal was to identifythose places that were doing a numberof different things under the headingof sustainability. These are places thathad implemented a comprehensivepackage of policies and programsranging from sustainable mobility, toenergy policy, to compact urban form,to reforms to their local governmentdecision-making structures to bettertake into account sustainability.

The main goals of the book are toidentify these places and then toextract lessons from them for Ameri-can cities. In the past we’ve had a lotof work that has been of the form thatsays that European cities are doinggood things and we should try tofollow their examples. But I think thetrick is to think about how those ideascan be adapted and applied to Ameri-can cities. So 70 percent of the book isabout what these European cities aredoing and what seems to work and

CONTENTS:

HOW TO FIGHTURBAN SPRAWL

Timothy Beatley

DECLINE OFSTRATOSPHERIC

OZONE ANDINCREASES IN UV

RADIATION

William Randel

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about 30 percent of the book is aboutwhat these stories mean for Americancities.

ER:ER:ER:ER:ER: Most of your cities are in North-ern Europe.

TB:TB:TB:TB:TB: Yes. There tends to be a strongNorthern European focus. In part it’s amatter of history that cities in thesecountries — particularly in theNetherlands, Germany, Denmark, andthe other Scandinavian countries —have tended to go the furthest in urbanenvironmental policies and programs,especially things like public transitand bicycles, ecological building,carbon dioxide reduction strategiesand solar, wind, and other renewableenergy sources.

Often an emphasis onsustainability has been at the nationallevel, but one Italian city, Bologna,was chosen because it’s been a leaderin a number of these categories. Also Ihaven’t in this study looked at all atthe Eastern European countries, whichof course are facing a different set ofissues, more serious in some ways,more basic.

One of the guiding premisesbehind my work in this area is thatcities, it seems to me, have to be a partof our environmental agenda. Espe-cially in the U.S., we tend to think ofcities and nature as being almost polaropposites: if something is urban, itcan’t be natural. Much of the historyof environmental protection has to dowith setting aside wilderness areas orbeing concerned about endangeredspecies or national forests. Veryimportant subjects, but they havetended to be outside of cities. We tendto think of the environment as some-

thing that we go to or we visit whenwe leave cities.

But a strong premise of my workis that cities not only are embedded inecosystems and are part of nature, butthat they have such a big impact onthe extent to which we use resourcesand the extent to which we areaffecting the environment that wecan’t ignore them. In fact, as theseEuropean cities show, cities can beplanned and managed and organizedin impressive ways which help us toreduce our ecological footprint.

ER:ER:ER:ER:ER: What is an ecological footprint?

TB:TB:TB:TB:TB: You can calculate the amount ofland necessary to support the lifestylesthat we lead, the food we eat, theenergy we use, the material we use tobuild our homes, the land area weneed to sequester the carbon thatwe’re generating to minimize globalclimate change. An urban populationhas an ecological footprint that ismany times larger than the spatialfootprint of that place. So a city likeLondon, which is one of the cities inmy book, exerts a demand on theenvironment, it requires a land base tosupport its population which is about125 times the spatial extent of the cityitself. It’s pulling in energy andresources and material to support thepopulation, and at the same time it’sthrowing out waste and pollution andresiduals of a variety of sorts.

So one of the main themes of mybook is to begin to see cities in thatway and to begin to, through a varietyof strategies and initiatives, minimizethat impact, minimize that ecologicalfootprint and develop more sustain-able relationships between the city and

its surrounding hinterland, hinterlandbeing defined quite broadly.

ER:ER:ER:ER:ER: You used the metaphor ofmetabolism, as if the city were alive.

TB:TB:TB:TB:TB: Yes, and this is certainly not myidea, but I think it’s a helpful way tothink about the city: as a series ofinputs of water and energy and food,and outputs of waste and pollution andso on.

Typically if we do acknowledge

Volume Seven Number TwoFebruary 2000

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those flows, we usually treat them in alinear and separated way, we don’t tryto think about them in a holistic ororganic fashion. One of the neat thingsabout many of the cities that I’mprofiling is that there are efforts nowto think about cities in this moreintegrated way so that we begin to seethat instead of waste being somethingthat we send away, we acknowledgethat it might serve as a productiveinput to something else. As we beginto connect inputs and outputs, webegin to think abouta more circularmetabolism, whatthe Swedes call anecocycle balancedcity. Cities likeStockholm havemade considerableprogress in thisdirection.ER:ER:ER:ER:ER: The point of theexercise being toimprove people'squality of life.

TB:TB:TB:TB:TB: Yes, I think it isimportant to ac-knowledge that thisagenda of sustain-able cities is verymuch about enhanc-ing quality of life.We often seeenvironmentalprotection as something that requiresthe sacrificing of the economy or jobsor some aspect of quality of life. Butwhat the European cities that I havestudied show is that you can createcities that reduce their ecologicalfootprints and at the same timeenhance quality of life and enhancethe livability of these places. You cansee that in a hundred ways.

ER:ER:ER:ER:ER: For example?

TB:TB:TB:TB:TB: For example, many of theseEuropean cities have made greatstrides to minimize the dominance ofthe automobile. These sustainablemobility strategies, while not takingthe automobile completely out of thepicture, certainly give people options,options to ride a bicycle, options totake public transit, options to join acar sharing organization. These areoptions that in most American citieswe don’t have and, for me, representan important enhancement of quality

of life.In doing this work and living in

the Netherlands for a year I got aroundon a bicycle and public transit as wellas walking. It was a rather rudeawakening when I came back to theU.S. and didn’t have those sameviable options. So quality of life andlivability are certainly major objec-tives under this goal of creatingsustainable places.

I think many European officialsand European citizens for that matter,recognize the importance of rethinkingplaces and cities. In fact the EuropeanUnion, to its credit, has been fundingmany of the initiatives that I talkabout. For example, there is now aEuropean Union-funded sustainablecities and towns campaign, which is anetwork of cities and towns aroundEurope that are interested in workingon the sustainability agenda andthey’re helping each other to become

more sustainable.There is, I think, a

greater priority andimportance placed onthe urban environmen-tal agenda in Euro-pean countries andcities than in the U.S.in part probablybecause it’s a moreurban place, and it hasa longer history ofcities and an urbansociety. It isn’t thecase that this is anagenda of a bunch ofenvironmental craziestrying to squash anenjoyable life orlifestyle that we’reused to having. Quitethe opposite, I think.

ER:ER:ER:ER:ER: What aboutcompact cities?

TB:TB:TB:TB:TB: In this country we are concernedabout urban sprawl and the inefficientuse of land and the extent to whichwe’re consuming land in most metro-politan areas at a much higher ratethan our population growth. Cities likePhoenix and Los Angeles and Denverare growing spatially much faster thantheir population growth. In mostEuropean cities there are similar

Co-housing allows for a sense of communitywithout sacrificing privacy.


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impulses to deconcentrate, but by andlarge the cities I’ve chosen for thebook have been able to maintain acompact, relatively tight urban formwhere you have densities that cansustain public transit and mixing ofuses and walkability, and asharper separation betweenurban and rural.

There are many goodexamples. Dutch cities likeAmsterdam and Groningenand indeed virtually everyDutch city, have a compacturban form; they emphasizeit. Amsterdam for example,has for many years aggres-sively pursued its owncompact cities policy. It hasa history of encouragingdevelopment in locationsthat build onto the existingcity and connect with theexisting city, and typicallythat means higher densitythan an American suburbandevelopment would nor-mally be. It means extend-ing public transit at thesame time or even beforehousing is completed, and providing ahigh degree of connectivity betweennew growth areas and the existingcity. It’s not this leap-frog develop-ment we see so much of here.

Amsterdam has done a marvelousjob of recycling urban lands. Forexample, there’s a rather largedocklands area that is now an area ofmajor housing close to the center ofthe city; a number of Dutch citiesfollow that pattern. The nationalgovernment in the Netherlands has anational compact cities policy which isdesigned to encourage this form ofcompact growth.

ER:ER:ER:ER:ER: Is that comparable to whatthey’re doing in Boulder, Colorado?

TB:TB:TB:TB:TB: Yes. In fact, in the book I talkabout Boulder. Boulder is relativelysmall — 100,000 people — butBoulder and Portland, Oregon, andnow a number of cities have adoptedurban growth boundaries in this

country. That’s the closest comparablemodel, I think, to the European urbanform.

There are in fact, some goodexamples and good signs around thiscountry that this more compact urbanform can in fact occur. It’s tougher todo it here, for a variety of reasons: wetreat rural land a little differently, andthere’s a strong emphasis given toprivate property rights, and we have amuch weaker system of planning anddevelopment control, and of coursethe financial and economic incentivesare different. You have gasolineprices, for example, that are $4 or $5 agallon in Europe compared to rela-tively cheap gasoline and energyprices here. That has an impact aswell.

ER:ER:ER:ER:ER: But there are good reasons whypeople move to the suburbs in theU.S.: it has offered a better life.

TB:TB:TB:TB:TB: Yes. In planning circles this isprobably the biggest issue right now.

There’s quite adebate aboutthis. Somewould argue,Yes, this isreally the kindof develop-ment peoplewant; otherswould arguethat, no,mostly thisreflects thefact thatpeople don’thave a lot ofchoices. It’smuch easier tobuild conven-tional subur-ban styledevelopmentthan it is tobuild more

mixed use, walkable compact citiesand so this tends to be the kind ofhousing available from which tochoose.

You can still live in suburbia inmany European cities, and you canstill live in a single family detachedhouse, but it’s less common. It tendsto be at a higher density and it tends tobe closer in, and you tend to have amuch greater range of housing optionsand living options than you do inAmerican cities. Probably the vastmajority of what we are buildingtoday still is in the conventionalsuburban style.

This is a big debate in planning,but I think it is instructive to look at

Compact urban form can provide densities that can sustainpublic transit, mixing of uses, and walkability.


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European cities and try to understandhow they’ve dealt with it. We havecities like Portland and Boulder andmany other places that want to buildand grow in more compact ways, and Ithink having some creative examplesand models of how to do that ishelpful. The book provides many goodexamples of creative compact devel-opment.

ER:ER:ER:ER:ER: That requires rethinking ourbuilding patterns.

TB:TB:TB:TB:TB: It was interesting to me to look atthe variety of alternative housing andliving ideas. Some of them havealready made their way to this coun-try; for example, co-housing began inDenmark and now there are more thana hundred co-housing projects underdevelopment here in the U.S., and it’sclearly a case of the European ideamaking its way here.

There are a number of otherideas: including, for instance, urbanecovillages, and creating compact,walkable urban spaces. One of thecontinuing trends in many Europeancities is towards the pedestrianizing ofstreets, particularly in city centers, andsome creative housing and livingarrangements are being promotedhere.

In most of these cities that I’velooked at, there are large numbers ofpeople living in the centers of cities.In this country people work in thecities and tend to go home at 5 or 6o’clock and cities tend to be prettydead. So there are efforts to promote,for example, housing over shops andto allow the mixing of housing in with

commercial and other kinds of uses. Anumber of those ideas are describedand discussed.

ER:ER:ER:ER:ER: What is co-housing?

TB:TB:TB:TB:TB: Co-housing is where you havehousing units clustered aroundcommon space; they typically have acommon house where you have mealsat night. Everyone has their ownindividual home but they tend to beclustered around a common pedestrianway or pedestrian area. This started inDenmark and has many advantagesfrom an environmental andsustainability point of view. But itseems also to respond to a desire thatmany people have, I think in thiscountry as well, for a sense of commu-nity and a sense of connection to otherpeople.

That’s essentially what co-housing is. Typically there’s a strongdemocratic decision-making elementto it as well. Very often the projectsare designed by the residents them-selves, and then typically they areorganized and managed throughcommittees and through collectivedecisions. So there’s a strong residentparticipation component to it as well.

That’s just one example, I think,

of a European living innovation thathas made its way over here. There aremany good examples by now of theiradaptation and again, the adaptation isimportant. It’s a little different when itmakes its way to this country.Charlottesville has one co housingdevelopment and you can find them inalmost every city. There are three orfour under development in Washing-ton, D.C., just up the road here.

ER: ER: ER: ER: ER: What about making citiesgreener?

TB:TB:TB:TB:TB: I’ve spent a lot of time looking atneighborhoods and developmentsaround Europe; it’s impressive thatyou can create relatively high densityhousing and living environments at thesame time that you incorporateelements of the natural environment,lots of trees and vegetation forexample. One of the interestingnotions in Europe is the green roof oreco roof, where you have this amazingecosystem on rooftops. Particularly ifwe’re going to move in the directionof more compact living, we’ve got tofind ways of greening almost every-thing: rooftops, walls, taking awaypavement and desealing the builtenvironment wherever we can. Thereare many strategies for that: taking

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sidewalks or places that wouldotherwise be paved over and usingthem to incorporate ecologicalelements. For example, a housingproject in the Dutch city of Utrechtthat I’ve been looking at recycles itsgray water, the fairly clean bath waterand kitchen water and has created areedbed treatment area in a placewhere you would normally just havepavement; it’s using that as a way oftreating and recyclinggray water. It’s anecological elementbuilt into a fairly highdensity housingproject. There aremany examples ofhow we can livecompactly at the sametime that we are ableto green and natural-ize our surroundings.

ER:ER:ER:ER:ER: Pavement is thephysical footprint of acity and it’s a disasterfor watersheds andwater quality. Soanything you could doto mitigate that wouldbe an improvementfor people’s quality oflife almost immedi-ately.

TB:TB:TB:TB:TB: Absolutely. Just to build on that,the European notion of an eco roofserves many of those functions. Oneof the important benefits of hese ecoroofs or green roofs is that they are agood strategy for managing stormwater. About 75 percent of the waterthat falls on a green roof is kept on theroof and used by the vegetation andonly a small portion of that watermakes its way into a city’s stormwater system. So green roofs end upbeing a marvelous strategy for

addressing this problem of the imper-vious surfaces that we’re creating incities.

I have many examples in mybook of buildings where by creatinggreen roofs the typical view ofrooftops that people look over, manyoffices look upon, typically they’reasphalt and gray and depressing, havebeen turned into meadows in the skythat people enjoy looking at. It has

enhanced the quality of working andliving in these buildings and in theseurban environments.

ER:ER:ER:ER:ER: Sounds like a bit of a structuralchallenge to me.

TB:TB:TB:TB:TB: There are intensive rooftopgardens where larger trees present realstructural problems. But for most ofthese ecological roofs you’re talkingabout a relatively thin substrate or alayer of soil, and typically that doesn’trequire any more structural strength

than you would normally need forsnow or would otherwise be engi-neered into the design.

The issue of what it costs isinteresting because it turns out thatthese green roofs have an importantfunction in protecting the life of theroof and the roof material: they shieldthe roof against ultraviolet rays andthey protect against freezing and

thawing and actuallycan extend the lifeof the roof to such adegree that they payfor themselves. So itturns out to be aneconomicallybeneficial strategyas well as environ-mentally desirable.

We’re notused to doing this inthe U.S. It’s not abuilding techniquethat we’ve usedmuch, although weare beginning to seesome examples. Infact, Portland,Oregon, has beenexperimenting withgreen roofs as anidea for dealing withits serious storm

water runoff problem.Green walls and green roofs and

urban forests and daylighting streamsthat have been covered over bypavement and creative ways ofpromoting natural drainage systemsare all trends in Europe. Instead ofbuilding complicated storm watercollection systems, they try to usenatural systems to treat rainwater andto treat runoff. There are manyexamples in Europe of using buildingslike schools and public buildings and

Green roofs can reduce runoff to storm sewers by 75 percentand protect the roof from UV light, freezing and wind damage.


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using their rooftops for creatinggardens and vegetation and solarpanels. There are many ways that theurban environment can be more greenand organic.

ER:ER:ER:ER:ER: What differences did you findwith transport and mobility?

TB:TB:TB:TB:TB: Many cities in Europe arecommitted to creating integrated,efficient, well-functioning transitsystems. A goodexample is Zurich,Switzerland, wherethey have a policyof giving priorityto their transit onpublic streets andtaking space awayfrom the automo-bile. Almost all ofthese cities, Zurichand Stockholm andBerlin havecoordinatedtransportation andland use, that’s oneof the main lessonsfrom these cities.They have in-vested in publictransit — thatcould mean anunderground metro, it could be a high-speed tram — at the same time thatthey plan for and build new housing,new development.

The American strategy is often,We’ll see later on whether the densitymight support public transit. We’renot sure, we’ll build the light rail laterif it’s warranted. The Europeanapproach is to do it all at the sametime so that you build in from the verybeginning mobility options forresidents. That’s been an effectivestrategy.

Cities like Freiburg, Germany,have been able to plan new housingareas and invest in the public transit atthe same time. They build a newhousing area and they extend thetransit, and they’ve been able to keepdown to some degree the use ofautomobiles and to allow for high useof public transit. So there’s generally amuch stronger commitment to transitin these cities than in most American

cities, with a few exceptions.

ER:ER:ER:ER:ER: It’s going to be difficult to weanAmericans from their cars.

TB:TB:TB:TB:TB: I think it’s a long-term proposi-tion, but I’m encouraged becausemany cities in the U.S. have madeconsiderable new investments intransit in recent years. More thantwenty cities have installed new lightrail systems in the last ten years or so:Dallas, St. Louis, Baltimore, Sacra-mento. Cities are beginning to recog-

nize that their traffic congestion andmobility problems can no longer besolved by simply building more roads.

We’re not going to do without theautomobile any time soon. I don’tthink anybody would argue that. Butwhat we can aspire to, I think, arealternatives, options. Give peopleoptions and give them a range of waysof getting around and a certainpercentage of the population is willing

and interested, peoplelike me, who wouldmuch rather get on atram or a train than getin their cars. Wecertainly see someamazing things happen-ing, for example, inWashington, D.C., withthe emergence of transitvillages around certaincorridors of the metrosystem there. There is acertain element of thepopulation interested inliving more compactlyand living with morereliance on transit, withthe automobile as partof the mix, obviously,but as a lesser partner inthe transportationequation.

I think the lessonfrom European cities is the amazingmobility and freedom that one hasthere. We tend to think of the automo-bile as something that enhances ourfreedom. But what I find is just theopposite: living in a European citywith lots of mobility options, wherethere is much less dependence on theautomobile, is actually freedom-enhancing, in my view. I’ve probablyridden on thirty-five transit systems inEurope, and they are all impressive tosome degree. One of the things I amespecially impressed by is the relative

Green roofs can extend the life of a roof enough to pay for theirinstallation and maintenance.


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freedom that both the young and theold tend to have in those places. In thiscountry kids are just waiting to turnsixteen or whatever the driving age isbecause they have no freedom reallybefore then. Mom and dad have to totethem around.

When you become too old and getto the point where you can’t safely usean automobile, what do you do? Anelderly woman said the other day in aWashington Post article, “You mightas well shoot me. That’s virtually theend of my life whenyou take away mydriving privileges.”If I were in those agegroups I would cer-tainly much rather beliving in a Europeancity where I have muchmore mobility andmany more options forgetting around. You seethat in these systems,you see elderly folksgetting on low carriagetrams, very easy to geton and off. It’s easy forthe handicapped to usethese systems as well.So I think there is afreedom enhancingaspect to these systemsthat we tend to forgetabout sometimes.

It’s also a matter ofequity. We spend a lot of money oncars and it affects especially those onthe lower end of the socioeconomicladder as well as the old and the veryyoung. I think there are many goodlessons to be learned from cities likeZurich, where they’ve made it apriority to make the transit faster,safer, more comfortable, easier to getaround from one place to another,easy to transfer from one mode toanother. They are always working toimprove the transit system, and it’s

easy to use these systems.

ER:ER:ER:ER:ER: That brings up the issue of safety.

TB:TB:TB:TB:TB: I certainly don’t have a very goodanswer for that. Nobody does. Thereare some very tough issues that aredifferent about American society andAmerican places. There are issuesabout safety that I think are different. Ithink one of the things we have to dealwith as urban planners is the wholeproblem of guns. I know gun control

is not always a very popular thing totalk about, but if you walk around anyEuropean city at night you don’t havethe fear of being shot. There are guns,but the chance of being killed by a gunis tiny compared to what it is here.

ER:ER:ER:ER:ER: You can sense the difference ifyou go to Toronto or Vancouver, rightacross our border.

TB:TB:TB:TB:TB: I think it certainly makes a bigdifference in how people use spaces

and whether they feel comfortable inpedestrian spaces at certain hours ofthe day, and whether they’re willing tolive in downtowns, for example.Those are tough issues. I have acolleague here on the faculty who saysthat we often overstate the dangers.There’s often a greater fear thanstatistics justify, but nevertheless,those issues are driving forces forpeople.

We have a lot of issues about thequality of education in cities, and

certainly the racialissue. I think it hasto be acknowl-edged that racismis a driving forcefor some people —or just call it thefear of people whodon’t look like you— and the desire tobe in a suburb maybe a way to getaway from otherpeople.

I think thoseare Americantendencies, andwhile I don’t knowwhat the answer is,I do think we haveto, in addition toworking on thephysical designkinds of things that

I tend to deal with and the environ-mental programs and policies, we alsohave to work on these other forces aswell.

So I would say, for example, guncontrol ought to be on the minds ofurban planners and environmentalists,even though we don’t tend to think ofit as an issue related to those things.

ER:ER:ER:ER:ER: This idea of the city as a livingorganism is just an extension ofrecycling, isn’t it?

Photovoltaic panels designed into the roofs of homes generateelectricity from sunlight.


9


TB:TB:TB:TB:TB: It really is. It’s just understandingthat the waste energy of a power plantcould be used to heat water, whichcould be used to heat buildings andhomes in a centralized district heatingsystem. The flare gas of the refinerycan be fed into the power plant andused to generate heat and power.There are all kinds of importantinterconnections and it’s just been alot easier to forget about them or toignore them in the past. This metaphorof metabolism is a powerful vision ofa city with a circular or balancedsystem where the outputs, the wastesand pollution, are turned around andused as productive inputs for otherthings.

We’re doing this a little bit in thiscountry under the heading of indus-trial symbiosis. But to this day theonly functioning models of that are inEurope, in cities like Kalundborg,Denmark, where they have a complexnetwork of different industries anddifferent activities that feed off eachother. I think that’s an importantstrategy for the future.

ER:ER:ER:ER:ER: What about renewable energyand solar power?

TB:TB:TB:TB:TB: I think one of the most impressivethings about what’s going on inEurope, particularly Northern Europe,is the emphasis on renewable energy,in particular, solar and wind. TheDanes and the Dutch and the Germansplace a lot of importance on support-ing renewable energy sources. Forexample solar power is being inte-grated into the built environment insome impressive ways. We’re seeingroof-integrated photo-voltaic panels asa common element in new housingprojects. In the Netherlands entire newcommunities are being designed to beenergy self sufficient through theintegration of photo-voltaics and

energy conservation and other ideas.There is this notion of using

public buildings to generate powerand using rooftops of homes togenerate power. There is this notion ofa zero-energy or an energy-balancedhome where the home generates asmuch power as it uses over the courseof the year and feeds the excess intothe power grid. These are becomingcommon ideas in some Europeancities. Many cities in combination withnational governments are providingsubstantial financial incentives topromote renewable energy.

ER:ER:ER:ER:ER: Renewable energy seems like agrowing market.

TB:TB:TB:TB:TB: I think so. I think it’s comingalong too in this country with thederegulation of the energy industryand the emerging ability of consumersto choose green power sources. But Ido think that there’s a powerful visionof cities as producers of their ownenergy. Bill McDonough,,,,, a formerdean here, likes to talk about theprinciple of living off solar income:instead of using nonrenewable fossilfuels, we can be living on the energyincome that we’re getting from thesun. I think many European citiesshow convincingly that we can do thatand that urban areas especially can beplaces where we mine this freeincome with much less environmentaldamage to the world.

ER:ER:ER:ER:ER: This will require political leader-ship to get industries and communitiesgoing in the right direction.

TB:TB:TB:TB:TB: I refer to this in the book asecological governance. Many of thesecities recognize that the place to startin becoming more sustainable is toreadjust their own policies. That is tosay, where do we get our energy to

fuel public buildings and street lightsand city hall? And many of these citiesare buying green power now orthey’re generating green power.

Many cities, like Albertslund,Denmark, have strong purchasingrequirements now; they’ve appliedsome pretty stringent standards to theproducts and services that they buy. Inthe realm of employee mobility, theyare encouraging city employees to getaround by bicycle or public transit.

Many cities are beginning tostructure local decisions in ways thatrecognize sustainability. For example,several London boroughs now areusing sustainability matrices as a wayof evaluating development projects.There are several pilot cities inGermany that are developing ecologi-cal budgets as a companion to thetraditional financial budget, acknowl-edging that we ought to know in thebudget cycle how much pollutionwe’re producing, how much of thelocal environment we are consuming,as well as how much environmentalrestoration we’re bringing about. Howmany trees are we planting, forexample, versus how many treeswe’re cutting down.

ER:ER:ER:ER:ER: Counting the externalities is justhonest bookkeeping.

TB:TB:TB:TB:TB: It’s honest bookkeeping, but it’snot something that we typically do inany systematic way. It can be part ofthe governance structure, and many ofthese communities are showing howthis can be done.

Literature Cited:Literature Cited:Literature Cited:Literature Cited:Literature Cited:

Green Urbanism: Learning fromEuropean Cities: Timothy Beatley2000 Island Press, Washington DCISBN 1559636823


10


TTTTTrends in Ozone Lossrends in Ozone Lossrends in Ozone Lossrends in Ozone Lossrends in Ozone Lossand Increased UVand Increased UVand Increased UVand Increased UVand Increased UVRadiationRadiationRadiationRadiationRadiation

Introduction:The 1995 Nobel Prize recognized

the scientists who first sounded thealarm about ozone loss in the strato-sphere. Ozone in the upper atmo-sphere acts as a sunscreen, shieldingus from harmful ultraviolet sunlight.Decreasing ozone means increasingUV and increasing damage to organ-isms exposed to sunlight. Howevermeasuring the ozone in the strato-sphere is rather like trying to measurethe average temperature of the planetagainst the background of seasonalchanges, weather, and El Niños. Manyyears' worth of careful measurementsare required to observe gradualchanges in both global temperatureand global stratospheric ozone. Arecent Science paper reports thattwenty years' worth of data showsclear evidence of ozone decreases inthe stratosphere1. The trend shouldreverse in the next ten to twenty yearsand then ozone is expected to recover.

In a related paper, scientists inNew Zealand have made a long timeseries of observations of how muchharmful UV is reaching the surface ofthe Earth2. In the summer of 1998-99sunburning UV was 12 percent higherthan it was earlier in the decade.These are the first results that directlylink ozone loss with an increase insunburning UV radiation.

We spoke with William Randelabout his work on stratospheric ozonemeasurements and also aboutMcKenzie's paper on increased UV.

ER:ER:ER:ER:ER: Dr. Randel, what is your train-ing?

WR:WR:WR:WR:WR: I received a Ph.D. in physicsfrom Iowa State University fifteenyears ago, and I came to the NationalCenter for Atmospheric Research as apostdoctoral fellow. My background isoriginally in atmospheric dynamicsrather than chemistry, but after acouple of years at NCAR I moved intothe chemistry division, where I’vebeen for thirteen years. My work herehas focused on the transport ofchemicals in the atmosphere andparticularly the global-scale processesthat are associated with transportingconstituents in the stratosphere. Ozoneis a useful tracer of air motions in thestratosphere, and you can learn a lotabout global circulation from under-standing ozone variability.

ER:ER:ER:ER:ER: When did ozone loss become aconcern?

WR:WR:WR:WR:WR: In the early 1970’s scientistspredicted stratospheric ozone coulddecrease as a result of human-causedemission of certain chlorine ornitrogen compounds. The scientiststhat won the Nobel Prize in chemistryin 1995 were the first to predict thatchlorofluorocarbons (CFC’s) woulddamage the ozone layer. CFC’s arestable (and inert) molecules that havelong lifetimes in the lower atmo-sphere. As they are slowly transportedinto the upper stratosphere, they aredecomposed by solar ultravioletradiation, freeing chlorine atomswhich destroy ozone. It was predictedthat the largest decrease in ozone dueto this mechanism would occur in theupper stratosphere where the chlorinewas liberated, around forty kilometersin altitude. But the predicted effectwas not very large; something like 5-10 percent depletion in the total

amount of ozone over 100 years.Analyses of historical ozone observa-tions through the early 1980’s did notshow evidence of large ozone losses.However, the situation changed whenthe Antarctic ozone hole appeared andwas recognized in about 1985. It wasstartling to observe large amounts ofozone disappear on relatively shorttime scales.

ER:ER:ER:ER:ER: Why was there so much uncer-tainty about whether ozone wasdeclining?

WR:WR:WR:WR:WR: There are large natural varia-tions in ozone on seasonal andinterannual time scales, so it takescareful analyses of satellite andground-based measurements to detecta small long-term change. After theozone hole was discovered in theAntarctic, scientists went back andcarefully reviewed historical satellitedata and ground-based measurements.

Each measurement system has itsadvantages and disadvantages. Asatellite gives you a global view, butthe satellite instrument can changeslowly over time and the measure-ments can drift. The ground-basedinstruments can be better calibrated,but they only tell you what’s happen-ing locally. So you need to study thetwo data sets in conjunction andcarefully interpret what’s happening ineach of them.

ER:ER:ER:ER:ER: Meanwhile there’s seasonalvariation and the occasional volcanoto keep things interesting.

WR:WR:WR:WR:WR: That’s exactly right. The netresult of the ozone trends evaluation in1991 was that scientists recognizedsignificant losses of ozone over midlatitudes of both hemispheres inaddition to losses over the South Pole.

The ozone trend estimates thatwere quoted in the 1991 UN Environ-


11


There are large natural variations in ozone on seasonal andinterannual time scales, so it takes careful analysis of satellite andground based measurements to detect a small long-term change.

mental Programme and World Meteo-rological Organization assessmentwere something like 6 or 8 percent perdecade change in column ozone overNorthern Hemisphere midlatitudes.The seasonal variation in columnozone is on the order of plus or minus30 percent, so you need a long recordof data in order to accurately measurea few percent per decade change.Careful analysesshowed that therewere significantozone losses occur-ring in mid latitudes.The next question iswhy are thesedecadal-scale lossesoccurring? To get a handle on thatquestion, you need to know at whataltitude the ozone is going away.

The UNEP/WMO assessment in1994 looked at global trends in thecolumn ozone and also compared thesatellite and balloon measurements.The 1994 assessment found largedifferences between the profile ozonetrends derived from balloons versuswhat were derived from satellite data.This was particularly true for the theSAGE (Stratospheric Aerosol and GasExperiment) satellite instruments.There are two separate SAGE instru-ments: SAGE I which flew from 1979to 1981, and SAGE II which waslaunched in late 1984 and continues tothe present. The 1994 evaluationshowed that the combined SAGEsatellite data had much larger trendsthan were inferred from the balloonmeasurements.

ER:ER:ER:ER:ER: What was the balloon datamissing?

WR:WR:WR:WR:WR: Well, as it turned out, it wasmore of a problem with the analysesof the satellite measurements. TheSAGE instruments watch the sun riseor the sun set through the limb of the

atmosphere, and by looking at thespectral lines of ozone or otherchemicals in the atmosphere you canderive the amounts of those specieswith good accuracy and high verticalresolution.

The problem is that retrieval ofspecies concentrations from thespectral radiance measurements ishard to do in practice because there’s

not just ozone in the atmosphere, butalso a host of other molecules likewater vapor or aerosols that interefere.In particular, there are large temporalvariations in the aerosol in the atmo-sphere due to volcanoes, and that cansignificantly influence what youderive for ozone trends if the signalsare not clearly separated.

ER: ER: ER: ER: ER: How do volcanoes interfere withozone measurements?

WR:WR:WR:WR:WR: Whenever a volcano goes off itreleases a large amount of aerosol intothe stratosphere, which then slowlysediments and is transported out of thestratosphere with a half-life of two tothree years. Mount Pinatubo eruptedin 1991 producing a huge source ofstratospheric aerosols, which thendecayed in time. The satellite ozoneretrievals need to carefully separatethe aerosol from the ozone signals, orthe ozone trends for the period will beoverestimated.

Estimates of trends from therevised data sets now show that theballoon and satellite estimates are inreasonable agreement, at least over theplaces where you can compare them.

As I mentioned before, a funda-mental problem with evaluating all ofthese ozone trends is that there is largenatural variability. The situation isanalogous to trying to detect smallchanges in temperature when youhave large seasonal and interannualvariations in weather systems (such asEl Niño). Trying to discern a smallchange in the background is analogous

for ozone.

ER:ER:ER:ER:ER: Isn’t there asatellite that looksdown through thecolumn and mea-sures ozone?

WR:WR:WR:WR:WR: Yes, but the problem with theones that look down is that they have arelatively low vertical resolution. TheSolar Backscatter Ultraviolet (SBUV)satellite instruments measure theozone profile in this manner, but havea coarse vertical resolution of approxi-mately 5 km (versus ~1 km for theSAGE measurements). These observa-tions use the fact that ozone stronglyabsorbs solar ultraviolet radiation, someasurements are made at severalwavelengths, some of which areabsorbed by ozone and others not. Butthe fundamental limitation of theSBUV instruments is the relativelypoor vertical resolution in the lowerstratosphere, where the action is interms of ozone depletion.

ER:ER:ER:ER:ER: How far out does the atmospherego?

WR:WR:WR:WR:WR: About one hundred kilometers.

ER:ER:ER:ER:ER: And where’s the ozone?

WR:WR:WR:WR:WR: The ozone is primarily locatedbetween 15 and 30 kilometers. Thelevel of peak concentration dependson latitude; it is higher in the tropics


12


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In 1991 scientists recognized there were significantIn 1991 scientists recognized there were significantIn 1991 scientists recognized there were significantIn 1991 scientists recognized there were significantIn 1991 scientists recognized there were significantlosses of ozone over mid latitudes of bothlosses of ozone over mid latitudes of bothlosses of ozone over mid latitudes of bothlosses of ozone over mid latitudes of bothlosses of ozone over mid latitudes of both

hemispheres in addition to losses over the South Pole.hemispheres in addition to losses over the South Pole.hemispheres in addition to losses over the South Pole.hemispheres in addition to losses over the South Pole.hemispheres in addition to losses over the South Pole.

than in midlatitudes. There is verylittle ozone below the tropopause.

ER:ER:ER:ER:ER: Tropopause being?

WR:WR:WR:WR:WR: The tropopause is the levelseparating the troposphere (loweratmosphere) from the stratosphere,which spans approximately 15-50.This division is based on the change oftemperature with altitude: in the loweratmosphere temperature decreaseswith height, while in the stratospherethe temperature is constant or in-creases with altitude.

I talked about the SAGE and theSBUV and the ozone sondes, andthere’s another measurement calledthe Umkehr, which is a ground-basedmeasurement.

ER:ER:ER:ER:ER: So that’s looking up?

WR:WR:WR:WR:WR: It’s looking up, but it’s a lot likethe SBUV, which looks down.

ER:ER:ER:ER:ER: How does that work?

WR:WR:WR:WR:WR: You measure a couple ofdifferent wavelengths of solar ultra-violet light, some that are stronglyabsorbed by ozoneand some that arenot. A series ofthese measurementsare made as the sunrises or sets, andinformation on thevertical ozone profile can be obtainedfrom an inversion algorithm. Thisprovides a low vertical resolutionestimate of the ozone profile, similarto the SBUV satellite data.

ER:ER:ER:ER:ER: Do they agree with the othermeasurements of the column ozone?

WR:WR:WR:WR:WR: That was something we specifi-cally wanted to go look at in our work.

The result is that they agree reason-ably well for the measurements madeover northern mid latitudes, where wecan make careful comparisons. That’sanother piece of information thatprompts confidence in the trendsderived from the balloons and fromthe satellites.

A key point regarding the ozonetrends is that there is a two-peakstructure in altitude, with separatemaxima near 15 and 40 km. This is afingerprint of the mechanisms leadingto ozone depletion. What is the causeof this structure, and do we understandit? This topic is addressed in detail inthe recent UNEP/WMO assessment.The theoretical and modeled under-standing of ozone depletion is some-thing that has been ongoing.

The basic theoretical understand-ing is that there are two reasons forthe observed double-peaked structureof ozone depletion. One mechanismprimarily occurs in the upper strato-sphere, with ozone losses largest near40 kilometers. This corresponds to theozone loss that was originally pre-dicted back in the 1970’s by thescientists that won the 1995 Nobelprize in Chemistry: Mario Molina,

Sherwood Roland and Paul Crutzen.They predicted that the increase inchlorine from human activities wouldcause ozone depletion near 40 kilome-ters in the upper stratosphere, and thatcorresponds to this observed upperlevel maximum.

There has been a lot of sophisti-cated numerical modeling experimentsto estimate what the spatial andtemporal structure of this upperstratosphere depletion due to chlorine

would be. The answer is that themodeled changes agree well with theobservations, both in terms of magni-tude of the trend and its spatialstructure (in latitude and altitude).This demonstrates that our under-standing of the ozone depletionmechanisms in the upper stratosphere

is very good. However,because there is relativelylittle ozone in the upperstratosphere, this 40 kmdepletion does not accountfor much of the observedcolumn ozone trends.

The question for total ozonefocuses on what is causing the lowerstratospheric trends (maximum near15 km). An important complication inthe lower stratosphere is that ozone isa very long-lived substance. Ozonehas a short photochemical lifetime inthe upper stratosphere (minutes orhours), but the lifetime graduallyincreases with lower altitude, until it isvery long-lived (seasons and years) in


13


The scientists that won the Nobel Prize inchemistry in 1995 were the first to predict

that chlorofluorocarbons would damage theozone layer.

the lower stratosphere. The result isthat transport by the atmosphericcirculation is crucially important forthe long-term variation of ozone in thelower stratosphere.

ER:ER:ER:ER:ER: Is there a barrier that keeps theatmopheric layers from mixing?

WR:WR:WR:WR:WR: The transport of ozone from theupper to the lower stratosphere due tothe general circulation is relativelyslow, with a time scale of months, butthere is not a barrier per se. Thetropopause acts in some respects like avertical barrier: the ozone staysprimarily in the stratosphere and is nottransported quickly below the tropo-pause.

ER:ER:ER:ER:ER: So the ozone that’sformed from smog in thetroposphere doesn’t gettransported up?

WR:WR:WR:WR:WR: That’s correct. Justlike in the stratosphere,there is a continualgeneration and destruction of ozone,with the ozone amount at any locationand time reflecting the balancebetween production, loss and atmo-spheric transport. Tropospheric ozonehas a photochemical lifetime of daysto weeks, so there is not a long-termbuild up unless the backgroundphotochemical conditions change(which does occur, in particular ascontinental areas become heavilypolluted).

To understand these relativelysmall decadal-scale variations, youneed to understand what is happeningto the meteorological and transportfields on interannual time scales. Asmall change in meteorology caninfluence where the ozone is and alsohow much there is.

Given that, the best currentunderstanding is given by takingnumerical models which include bothchemistry and transport. This is a verydifficult problem to quantify for long-term variations, due to uncertainknowledge of the details of transportand temperature-dependent chemistry.The last UNEP/WMO assessmentincluded simulations of past variabilityand predictions of future ozoneamounts from ten different modelinggroups around the world. Theseinclude the observed increases inatmospheric chlorine and other tracespecies, and each group uses modelswith varying levels of sophisticationfor different transport or chemicalaspects of the problem.

Each of the ten different modelcalculations of past ozone change hadsome level of agreement with theobserved trends, in terms of simulatingthe spatial and temporal characteristicsof the trends. This agreement promptsconfidence that we understand thebasic physics of ozone depletion dueto increasing chlorine (which is themechanism producing the modelchanges). The fingerprint looks right.However, if you look at the details ofany one model output there can be afair amount of difference with theactual year-to-year observations. Thisis an ongoing process in that themodel simulations are continuallybeing improved and tested to under-stand the processes controlling ozonein the lower stratosphere. My ownperspective is that we understand the

ozone loss processes to first order, butmany details await continued studies.

ER:ER:ER:ER:ER: What do you mean by thefingerprint?

WR:WR:WR:WR:WR: The fingerprint is the space andtime variation of the changes in ozone.How do the model calculations matchthe latitude, altitude and time variationof the observations?

In addition to the decadal-scaletrend patterns, another fingerprint thatillustrates model behavior is simula-tion of the large ozone losses after thePinatubo volcanic eruption in 1991.There were fairly large losses incolumn ozone, up to 10 percent insome places, but these losses had a

peculiar structure versuslatitude and time. They werebiggest at high northernlatitudes in wintertime,because the volcanic aerosolsmost effectively destroyozone at the coldest tempera-tures. Thus the physicalmechanism which removed

ozone happened mainly in winterconditions. A map of ozone lossesthen acts as a type of fingerprint forthis volcanic signal, and this could becompared in detail with what com-puter models calculated for Pinatubo.What is meant by a fingerprint is notone particular detail, but a number ofcharacteristics both in space and timewhich identify the phenomenon ofinterest.

It turns out that heterogeneouschemistry which occurs on atmo-spheric aerosols is very important forozone behavior in the lower strato-sphere. When a large volcano erupts,there is enhanced chemical destructionof ozone. For the eruption of Mt.Pinatubo in 1991, the global ozonedecreased by several percent, andlocally it decreased up to 10 percent.So you need to understand exactly


14


McKenzie's group was the first to quantify a long-McKenzie's group was the first to quantify a long-McKenzie's group was the first to quantify a long-McKenzie's group was the first to quantify a long-McKenzie's group was the first to quantify a long-term change in UV and confirm that the changesterm change in UV and confirm that the changesterm change in UV and confirm that the changesterm change in UV and confirm that the changesterm change in UV and confirm that the changes

were attributable to observed ozone losses.were attributable to observed ozone losses.were attributable to observed ozone losses.were attributable to observed ozone losses.were attributable to observed ozone losses.

how these aerosol effects are physi-cally affecting the ozone. Details ofincorporating aerosol microphysics inglobal circulation models leads todifferences in the output.

ER:ER:ER:ER:ER: What about McKenzie’s work?

WR:WR:WR:WR:WR: The topic of uncertainties inmeasuring ozone in regards to long-term trends apply also to the questionof trying to measure long-termchanges in surface ultraviolet (UV)radiation. Because UV is absorbed bystratospheric ozone, if you reduceozone you get more UV. ButMcKenzie's group was the first thatwas able to quantify along-term decadal-scalechange in UV and confirmthat the changes wereattributable to observedozone losses. There aren’tlong records over largeareas that allow confident estimates ofdecadal time scales; consistenthistorical measurements just were notmade.

ER:ER:ER:ER:ER: Until now

WR:WR:WR:WR:WR: Until now. The shorter-termrecords have occurred mostly in theNorthern Hemisphere, and in generalthere is more natural year-to-yearvariability in ozone in the NH than inthe Southern Hemisphere. So what hasbeen published to present has mostlyshown lots of ups and downs oninterannual time scales.

McKenzie’s group were able tomake long-term measurements in aregion where ozone trends are rela-tively large and natural variability isless (in the high latitude SH). Theywere very careful to make enoughmeasurements during cloud-freeconditions so that they could clearlyseparate the effects of ozone changes(clouds also affect the amount of UV

reaching the surface). But mostimportantly, they have been makingtheir measurements for a long enoughtime that they could identify a trend.Furthermore, they measured severaldifferent frequencies of ultravioletlight, including some that are notstrongly absorbed by ozone. The UVwavelengths aborbed by ozoneshowed a clear trend, while none wasfound for the other measurements.

ER:ER:ER:ER:ER: Is the stratospheric ozone ex-pected to recover?

WR:WR:WR:WR:WR: Our estimates of ozone recoverydepend on two things. One is the

projection of the amount of chlorineand other ozone-depleting substancesin the future atmosphere. These arebeing continually measured at anumber of locations around the globe,and there are good estimates of theglobal budgets of these chemicals.Some of them maximized and aredecreasing, in response to the regula-tions put in place by the MontrealProtocol agreement (and subsequentamendments). Other compounds showa flat time variation, and some speciesare continuing to increase; the detailsdepend on the amount released and thedifferent lifetimes in the atmosphere.If you add up all the chlorine species,there was a peak in the lower atmo-sphere in about 1993-94, and it hasbeen slowly decreasing afterward.

There are accurate satellitemeasurements of hydrochloric acidnear 50 kilometers from satellites foralmost ten years now. About 80percent of this HCl originates fromanthropogenic chlorine. These upper

stratospheric measurements show aclear increase up till about 1997, andthen they turned over and haveshowed a decrease since then. Thisreflects the lower atmosphere changes(peak in 1993-94) with a several yeartime lag; this lag represents the transittime for chemicals to travel from thelower to the upper atmosphere.

These projections of futurechemical content of the atmospherecan be incorporated into the variousnumerical models (used to explainpast variability) and predict ozonechanges over the next several decades.The result is that we expect themaximum decrease in ozone to occur

between the present timeand the next two decades,followed by slow recov-ery. This uncertainty inprediction of the mini-mum reflects uncertain-ties in details of the

model simulations.

ER:ER:ER:ER:ER: Doesn't the amount of ozone inthe stratosphere influence climatechange?

WR:WR:WR:WR:WR: Very much so. A number ofstudies in the last five years haveincorporated ozone trends intocalculations of climate change due tocarbon dioxide and other greenhousegases. The results show that it makes asignificant difference in the patterns oftemperature change you predict if youinclude the effects of ozone depletion.Approximately 30 percent of thewarming which would have occurredat the surface over the last 20 yearswas masked by the effects of strato-spheric ozone depletion.

ER:ER:ER:ER:ER: So ozone depletion is offsettingsome of the heating from greenhousegases?


15


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Blood Lead Levels in American Children:Blood Lead Levels in American Children:Blood Lead Levels in American Children:Blood Lead Levels in American Children:Blood Lead Levels in American Children:Bruce LanphearWhat’s Causing the Extinction of TopWhat’s Causing the Extinction of TopWhat’s Causing the Extinction of TopWhat’s Causing the Extinction of TopWhat’s Causing the Extinction of TopPredators? Predators? Predators? Predators? Predators? Joshua Ginsberg and RosieWoodroffe

FebruaryFebruaryFebruaryFebruaryFebruary

The Costs of Introduced Species:The Costs of Introduced Species:The Costs of Introduced Species:The Costs of Introduced Species:The Costs of Introduced Species: DanielSimberloffAlternative Scenarios for the 21Alternative Scenarios for the 21Alternative Scenarios for the 21Alternative Scenarios for the 21Alternative Scenarios for the 21 ststststst Century: Century: Century: Century: Century:Allen Hammond

MarchMarchMarchMarchMarch

Are Fish Farms Sustainable? Are Fish Farms Sustainable? Are Fish Farms Sustainable? Are Fish Farms Sustainable? Are Fish Farms Sustainable? RebeccaGoldburgHow Do Tropical Forests Recover fromHow Do Tropical Forests Recover fromHow Do Tropical Forests Recover fromHow Do Tropical Forests Recover fromHow Do Tropical Forests Recover fromLogging? Logging? Logging? Logging? Logging? Preston Aldrich

AprilAprilAprilAprilApril

A New Threat to the Monarch ButterflyA New Threat to the Monarch ButterflyA New Threat to the Monarch ButterflyA New Threat to the Monarch ButterflyA New Threat to the Monarch ButterflyMigration: Migration: Migration: Migration: Migration: O.R. TaylorTracking Migratory Birds in the Neotropics:Tracking Migratory Birds in the Neotropics:Tracking Migratory Birds in the Neotropics:Tracking Migratory Birds in the Neotropics:Tracking Migratory Birds in the Neotropics:Peter Marra

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Why Did Yellowstone Burn? Why Did Yellowstone Burn? Why Did Yellowstone Burn? Why Did Yellowstone Burn? Why Did Yellowstone Burn? Linda Wallaceand Grant MeyerGlobal Warming and Changes in PlantGlobal Warming and Changes in PlantGlobal Warming and Changes in PlantGlobal Warming and Changes in PlantGlobal Warming and Changes in PlantCommunity Structure: Community Structure: Community Structure: Community Structure: Community Structure: Richard Alward

JuneJuneJuneJuneJune

Using Tree Rings to Reconstruct ClimateUsing Tree Rings to Reconstruct ClimateUsing Tree Rings to Reconstruct ClimateUsing Tree Rings to Reconstruct ClimateUsing Tree Rings to Reconstruct ClimateHistory: History: History: History: History: David StahleMeasuring Greenland’s Ice Sheet: Measuring Greenland’s Ice Sheet: Measuring Greenland’s Ice Sheet: Measuring Greenland’s Ice Sheet: Measuring Greenland’s Ice Sheet: WilliamKrabillPrairie Chicken Conservation: Prairie Chicken Conservation: Prairie Chicken Conservation: Prairie Chicken Conservation: Prairie Chicken Conservation: Jeffrey Brawn

JulyJulyJulyJulyJuly

The Long Reach of El Niño: The Long Reach of El Niño: The Long Reach of El Niño: The Long Reach of El Niño: The Long Reach of El Niño: MichaelMcPhadenEffects of Increased Atmospheric CarbonEffects of Increased Atmospheric CarbonEffects of Increased Atmospheric CarbonEffects of Increased Atmospheric CarbonEffects of Increased Atmospheric CarbonDioxide on Coral Reefs: Dioxide on Coral Reefs: Dioxide on Coral Reefs: Dioxide on Coral Reefs: Dioxide on Coral Reefs: Joan KleypasBenefits of Marine Reserves: Benefits of Marine Reserves: Benefits of Marine Reserves: Benefits of Marine Reserves: Benefits of Marine Reserves: Craig Dahlgren

AugustAugustAugustAugustAugust

Time to De-List Grizzlies? Time to De-List Grizzlies? Time to De-List Grizzlies? Time to De-List Grizzlies? Time to De-List Grizzlies? David MattsonA Dead Zone in the Gulf of Mexico: A Dead Zone in the Gulf of Mexico: A Dead Zone in the Gulf of Mexico: A Dead Zone in the Gulf of Mexico: A Dead Zone in the Gulf of Mexico: NancyRabalaisSome Constructive Criticism for the SierraSome Constructive Criticism for the SierraSome Constructive Criticism for the SierraSome Constructive Criticism for the SierraSome Constructive Criticism for the SierraClub: Club: Club: Club: Club: Douglas Taylor

SeptemberSeptemberSeptemberSeptemberSeptember

Does One Exotic Pest Deserve Another?Does One Exotic Pest Deserve Another?Does One Exotic Pest Deserve Another?Does One Exotic Pest Deserve Another?Does One Exotic Pest Deserve Another?Robert OhmartTrading Air Pollution Permits: Trading Air Pollution Permits: Trading Air Pollution Permits: Trading Air Pollution Permits: Trading Air Pollution Permits: Jay CogginsFire Hits the Tropical Forestry Initiative: Fire Hits the Tropical Forestry Initiative: Fire Hits the Tropical Forestry Initiative: Fire Hits the Tropical Forestry Initiative: Fire Hits the Tropical Forestry Initiative: CarlLeopold

OctoberOctoberOctoberOctoberOctober

Drug Resistant Tuberculosis: Drug Resistant Tuberculosis: Drug Resistant Tuberculosis: Drug Resistant Tuberculosis: Drug Resistant Tuberculosis: Jeffrey StarkeForest Responses to Greenhouse Gases:Forest Responses to Greenhouse Gases:Forest Responses to Greenhouse Gases:Forest Responses to Greenhouse Gases:Forest Responses to Greenhouse Gases:Evan DeLuciaJobs Versus the Environment? Jobs Versus the Environment? Jobs Versus the Environment? Jobs Versus the Environment? Jobs Versus the Environment? EbanGoodstein

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Does It Matter What We Do to the World’sDoes It Matter What We Do to the World’sDoes It Matter What We Do to the World’sDoes It Matter What We Do to the World’sDoes It Matter What We Do to the World’sOceans?Oceans?Oceans?Oceans?Oceans?An Address to the Ecological Society ofAn Address to the Ecological Society ofAn Address to the Ecological Society ofAn Address to the Ecological Society ofAn Address to the Ecological Society ofAmerica: America: America: America: America: Sylvia Earle

DecemberDecemberDecemberDecemberDecember

Fire History of Southern California: Fire History of Southern California: Fire History of Southern California: Fire History of Southern California: Fire History of Southern California: JonKeeleySeven Steps to a Healthier Planet: Seven Steps to a Healthier Planet: Seven Steps to a Healthier Planet: Seven Steps to a Healthier Planet: Seven Steps to a Healthier Planet: John RyanBenefits of Marine Reserves Revisited: Benefits of Marine Reserves Revisited: Benefits of Marine Reserves Revisited: Benefits of Marine Reserves Revisited: Benefits of Marine Reserves Revisited: AlanHastings


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WR:WR:WR:WR:WR: That’s right. And if we areindeed near the minimum of ozonedepletion, then perhaps this effect willnot mitigate climate warming in thefuture.

I think in all these predictions ofozone recovery and greenhouse gasrelated climate change there aresubstantial uncertainties in the details.However, as time goes on, climate andchemistry models become better, asevidenced by more accurate simula-tion of past changes. Plus, there isreasonable agreement betweendifferent models, and our knowledgethat the fundamental physical basis ofthese models is correct. The fact thatan increase in greenhouse gases willact to warm the lower atmosphere issound. But for accurate prediction ofthe details, you need to incorporatestratospheric ozone changes into thesimulations (along with changes inlower atmosphere sulfate pollution,ocean variability, and a number ofother aspects of the climate system)

Literature Cited:Literature Cited:Literature Cited:Literature Cited:Literature Cited:

1 ) Trends in the Vertical Distributionof Ozone. WJ Randel, RS Stolarski,DM Cunnold, JA Logan, MJNewchurch, JM Zawodny 1999

Science 285: 1689-1692

2) Increased Summertime UV Radia-tion in New Zealand in Response toOzone Loss. R McKenzie, B Connor,G Bodeker 1999 Science 285:1709-1711


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