i. forms of climate change ii. long-term change iii. climate cycles iv. human- induced wetlands and...

I. Forms of Climate Change

II . Long-Term Change

III. Climate Cycles

IV. Human- Induced

WETLANDS AND CLIMATE CHANGE

I . Long term - Global Warming• Sea Level Rise/Subsidence• CO2 Rise

Ocean Acidification• Temperature RiseII. Climate Cycles• Regime Shifts• El Niño /NAO• Precipitation• DroughtIII. Human- Induced• Freshwater inputs• Sedimentation• Circulation

Hypoxia• Urban development - wastewater

AT THE ROOT OF MUCH CLIMATE CHANGE:

Rising CO2

Warming

Acidification

Sea Level Rise

Changing circulation

Causes of Sea Level Rise•Warming Ocean - Expansion of seawater

•Melting Ice

IPCC Report/Andrew Weaver

•3000 y ago to 1900 : Rise of 0.1-0.2 mm/y

•Today: Global Average of 3mm/y

•End of Century: 30 to 45 cm increase

•Does not account for Greenland melting, which could add 19-58 cm.

•Complete melting of Greenland (1700 years) would occur with a 2.5-3oC rise in temperature•Greenland melting will lead to a 7 m rise in sea level.(Covering much of W. Europe/ Manhattan)

Sea-Level Rise in Wetlands

Measuring Elevation

• SET Table•Feldspar Marker•Pb-210, Cs 137•Tidal Gauges

Rates of accretion compared with rates of sea-level rise.But: measurements are short-term and rate of rise is unknown.

SEA-LEVEL RISEPast measurements:

0.86 mm/y Australia Mangrove encroachment2.6-3.9 mm/y Mid Atlantic Salt Marsh loss (10-20%)

Loss of habitat for 9 migratoryshore birds that use the marsh

2.5 mm/y New England 1.2 cm/y ? (subsidence) Chesapeake Bay0.48 mm/y (SL rise - 142 y) North Carolina0.6 mm/y (rise - 200 y) Wadden Sea Netherlands

Coastal erosion is 100x the rate of sea level rise.

SubsidenceSan Francisco Bay - 3-5 mm/y, Coyote creek 10-25 mm/yWadden Sea - 1-6 mm/ydue to compaction, oil and gas extraction (Wadden Sea, LA)

Accretion must exceed sea level rise for wetlands to persist

(deposition + plant biomass)Accretion Rates:0-11 m/y (Wadden Sea)Highest in summer, young marshesShort-term rates are higher than long-term rates due to compaction

van Wijnen and Bakker - At current rate of sea level rise it will be500 y until low marshes of the Wadden Sea deteriorate.(may no longer be true)

QuickTime™ and aPhoto - JPEG decompressor

are needed to see this picture.

Accretion rates are higheron the Gulf than Atlantic coasts

Accretion rates on the open coastare higher in the absence of hurricanes but rates inland arelower.

Net accumulation ratesindicate substantial loss of marsh in Louisiana

Turner et al. Science 2006

Wetland sedimentation from Hurricanes Katrina and Rita

130 * 106 mt sediment accumulated in coastal wetlands of Gulf Of Mexico when Katrina and Rita crossed shore in 2005

278 * 106 mt accumulated in shallow subtidal waters

= 12 % of Mississippi load/y

= 5.4% of pre levee flood deposits/y

=208 times amount deposited in river diversions

Authors conclude that hurricanes can provide the inorg. Sedimentsneeded for a healthy wetland.

Sea-Level Effects on Wetlands•Landward progression, rate determined by rate of SL rise•Rates of accretion decline over time

due to to rise in elevation which reduces inundation timeAccretion = deposition-erosion

•Erosion at seaward front•Increased peat saturation, salinity, sulfide conc., decreased O2

•Altered zonation patternsWarren and Niering (1993) - Juncus to forbs (Triglochin) S. patens to S. alterniflora & Distichlis spicata

•Low marsh at greatest risk (greatest increase in inundation)•Where seawalls or development form landward boundary, marshes will become narrowerGiven that marshes move, should we be trying to maintain status quo?

Sea Level and Mangroves

Mangroves are likely to be favored over marsh grass where they co-occur under conditions of rising sea level and warming waters. Expecially if grasses are stressed.

Alternatives for protecting wetlands from rising sea level(USA EPA)

1) Increase wetlands’ ability to keep pace with sea level (supply sediment) - e.g., supply sediment2) Protect coastal barriers (barrier islands, spits)3) Create no development buffers4) Construct tide protection systems (dikes, pumps, gates)

SAV Response to Climate Change - Jacoby USGS•A rise in sea level along the Gulf Coast will lead to changes in hydrology, salinity, and other abiotic factors that impact SAV.

•While projected climate changes may be under debate, changes in regional hydrology, salinity and nutrient regimes are certain

•While native SAV plays an important role in estuarine communities, invasive, exotic SAV species can play a harmful role ecologically, by out-competing and replacing native species. Several of these alien SAV species can, under certain conditions,become so prolific they create water quality problems and hinder navigation. Changes in SAV communities thus have profound implications for local and regional biota, shoreline geomorphology, biogeochemical cycles, and human activities.

The productivity, distribution, and extent of SAV are extremely susceptible to the direct and indirect effects of global change processes.

Excerpts of "Climate Change and its Impacts: A Global Perspective" Some recent results from the UK research programme; Department of the Environment Transport and the Regions, The Met Office, December 1997 & November 1998.

•Without specific adaptation, sea-level rise will significantly increase theflood risk to coastal populations (e.g., via loss of wetlands)

•Coastal wetlands are expected to decline due to sea-level rise, with the largest losses around the Mediterranean and Baltic and on the Atlantic coast of Central and North America.

•There is a commitment to sea-level rise which means that some impacts will continue to occur for centuries even if climate change is halted.

Increased CO2 Concentration

•predicted: 0.5% rise per year, increase to 500 ppm •doubling of pre industrial levels by 2100•Wetland plant response studied by: -growth at natural CO2 springs -artificial enhancement (tundra, brackish marsh, salt marsh)

3.6 percent of Earth’s land area that is now wetlands may stockpile between 10 and 30 percent of all the carbon stored on planet surface

loss of wetlands may release this as CO2 back into the atmosphere

Carbon dioxide chambers in Maryland brackish marsh study

C3 vs C4 plants

•Plants are only 80% efficient at removing CO2 for photosynthesis, and efficiency decreases at higher temperatures

•C4 plants have a mechanism to increase concentration of CO2 at Rubisco site, increasing efficiency of CO2 uptake

•C4 - involves 4 carbon intermediate in the outer cells, but requires ATP… most effective in warmer climate where ratios of O2 and CO2 change.

•Carbon storage in C3 plants may also be increased by a decrease in the respiration rate of plants--the rate at which stored carbon compounds are converted into CO2, water and energy.

•Consistent increase in photosynthesis and a decrease in respiration was observed in a C3 brackish marsh dominated by Scirpus olneyi exposed to 700 ppm CO2(twice ambient concentrations) (Arp and Drake 1991; Drake 1992; Arp et al. 1993, Drake et al. 1996a).

•There is no direct effect of CO2 on C-4 plants because the carbon fixing enzyme is not oxygen inhibited

•Photosynthesis is stimulated by elevated CO2 in C3 plants becausethe enzyme that helps fix CO2 into sugars is less inhibited by oxygen in the leaf at high CO2 concentrations.

•Increased carbon assimilation in C-3 dominated marsh but notin C-4 marsh. But effects change over time.

•Tundra experiments show CO2 stimulation of C fixation is short lived (1 year), due to nutrient limitation







CO2 effects on plant water use

•The size of the stomatal opening is controlled by the concentration of CO2 and water vapor inside the leaf,

•Elevated concentrations of atmospheric CO2 tend to decrease the size of the stomatal opening, which results in a decrease in transpiration.

•Elevated CO2 has significantly decreased water loss in both C3 and C4 communities in MD marshes by as much as 30%. This decrease in water loss paired with the increase in carbon uptake, has translated to an increase in plant water use efficiency, in some years an increase of over 100% (Drake 1992).

• Elevated CO2 may help some wetlands stay wetter

What are effects of increase assimilation efficiency and water use efficiency?

•litter decomposition•plant-microbe interactions,•plant-animal interactions•plant-plant interactions

C3 plants at elevated CO2 levels:•Increased resistance to fungal damage•Greater N2 fixation by root bacteria•Increased methane formation, nematodes, foraminifera • Shift in C3/C4 composition

Anne Marsh, National Wetlands Newsletter, Vol. 21, No. 3.(1999)Dacey et al. 1994; Drake and Ruiz, unpublished dataArp et al. 1993

CO2 Effect on Soil Respiration(Ball and Drake 1998)

Hypothesis - Increased resource use efficiency may stimulate soilmicrobial processes, increasing nutrient turnover and leading to increased soil respiration and soil carbon accumulation.

Observations: Soil respiration rates in chambers with elevated CO2

were always higher than in chambers with ambient CO2. Largereffect with C3 plants present than C4 plants (related to root biomassand root exudation response to CO2).

BUT: Uncovered soil respiration rates always higher than chamberrates. Could be related to limited insect access in chambers.

Tropical plants - respiration rate not stimulated (nutrient limitation?)

CO2 Effect on N2 Fixation(Dakora and Drake 2000)

Examined in salt marsh via: nitrogenase activity (acetylene reduction method)15N incorporation via 15N2 gas

Taxon Nitrogenase activity 15N incorporation

Scirpus olneyi 35% rise 73% riseSpartina patens 13% rise 23 % rise

•Results comparable to stimulation of photosynthesis by CO2.•Indicates that increased C fixation of plants will be passed ontoendophytic and below ground microbes



Dakora and Drake 2000

Mangroves:•Enhanced water content•May not increase canopy photosynthesis growth and litterfall•Increased rate of vertical accretion•Species responses will vary

Seagrasses:•Excess epiphyte growth•Increased ratio below: above ground biomass•Possible increase in C:N ratio -• changing quality as food

Response to Elevated CO2



Ocean acidification• CO2 dissolves in seawater to make carbonic acid

• Carbonic acid is corrosive to the shells and skeletons of many marine organisms

Photo: Missouri Botanical Gardens

Corals

http://www.biol.tsukuba.ac.jp/~inouye

Calcareous plankton

Caldeira & Wickett, Nature, 2003

NOAA (Feely et al., in press)Atmospheric CO2 = 785

ppmAtmospheric CO2 = 280

ppmAtmospheric CO2 = 370

ppm

Atmospheric CO2 = 680 ppm

Atmospheric CO2 = 780 ppm

Future ocean chemistryMost corals require over 3.5 saturation

Small pH changes can affect growth of sea urchins

What will happen to wetlands as oceans acidify?

Wetland calcifiers include:

• Bivalves (mussels, clams, oysters, scallops)

• Foraminifera

• Fish (otoliths)

Processes that could be affected by pH

Decomposition, Photosynthesis, N cycling

Methane as a greenhouse gas

Sources of methane: (1) anaerobic decay in wetlands(2) anaerobic fermentation in cattle rumens (3) natural gas leakage

Current levels:1.7 ppm, rising at 1-2% per yearWarming may accelerate methane releaseCO2 additions will stimulate methane release

Sedimentation

Causes:

•deforestation•logging•grazing•road building•development:

plant removal, paving•FENCES

New Zealand - can receive 10 y delivery in 1 day.

Experimental application of terrigenous slurry (Lohrer et al.)

•Number of indiv. declines with 7 mm deposit•Number of species declines with 7 mm deposit•Massive change in macrobenthos community structure

Temperature Rise

•Global Warming:•More warming over land than ocean (land warms faster)•More warming at high than low latitudes (albedo)•More warming in N. than S. hemisphere (more land in N)•More warming in winter than spring (albedo - ice)

•Global trends toward hotter, dryer climate

Warming and Oxygen•Warmer, saltier water holds less oxygen (seawater incursion)

•Warmer water increases oxygen demand by organisms

•Biota near thermal limits may not have circulatory capacity to supply oxygen

•Changes in organisms distributions, local extinctions are likely.

•DO water quality standard for estuaries: 5 mg/l•Small temp. increase drops estuaries below the standard (Texas)

•Levings et al. 120 exotic species in GA - small change in tempcan lead to significant changes in abundance in species whoseN and S range are limited by water temperature.

Mangroves: Temperature Rise

•Expansion into higher latitudes•Increase in photosynthesis, respiration, litterfall•Increased rates of microbial decomposition•Increase in plant and animal biodiversity•Change in densities, composition, growth and reproduction•Reduced rate of vertical accretion.

Wetlands can modify climate•Wetlands cover 6% of land surface but contain 35% of theterrestrial biosphere carbon pool. (770Gt) Of this 540 Gt is peat.

•Wetlands are carbon reservoirs. These will supply C to theatmosphere if water levels are lowered or land use increasesoxidation of soils. Significant CO2 can be released.

•Wetlands release C as CO2, dissolved C and methane

•3-4oC warming would eliminate 85% of wetlands in So. Europe

•1 m rise in sea level would eliminate 50% of coastal wetlands.

•Major threats to biodiversity

Marshall Pielke, Steyaert Nature 426: 29 ( 2003)

•Land use is one way humans affect climate

•Extensive drainage of So. FL wetlands to convert land intowinter vegetable, sugar cane and citrus crops

•Severe freeze on Jan 19 1997 led to 300 million loss in vegetable/sugar cane agriculture, and displaced 100,000 migrant farm workers

•Computer simulation of climate under pre 1900 and 1993 land-use conditions demonstrates different minimum temperatures asa function of land use.

•Draining wetlands leads to more frequent, more intense freezes in south Florida



Marshall et al.2003

pre 1900 1993

landuse

MinTemp

Drought•Longer periods without precipitation•Higher maximum temperature•Drier conditions•Increased temperature and precipitation variability

Mississippi R. drought 1998-2001 - low river input, low water levelsled to “Brown Marsh Event” in FL, TX, LA wetlands>100,000 acres of marsh affected in patches 300 m2 to 5 km 2.50-100% plant mortality, pH drop from 7 to 4Elevated Na, K, oxidized ironS. alterniflora and S. patens affected. (C-4 plants)Avicennia germinans and Juncus roemerianus unaffected (C-3)

Experiments show moisture and iron had big effects on S.alterniflora.

Brown Marsh EventThe Saltwater Marsh Dieback was declared an emergency by Louisiana Governor Mike Foster in the form of Executive Proclamation #55-MJF-2000 issued on October 23, 2000. In response, Congress allocated approximately three million in funds through the National Atmosphericand Oceanic Administration to the Louisiana Department of Natural Resources (LDNR) to examinecauses and effects of the Brown Marsh phenomenon.





Black mangrove (Avicennia) made major incursions into the salt marsh.

El Niño Southern OscillationWill increase in frequency

•Compaction is proportional to Southern Oscillation Index (drought)Higher compaction - mores subsidence, greater Grey Mangroveencroachment of salt marsh.

S. Williams - 1997-8 El Niño in Southern California - 3oC warmer in seagrass bedZostera declines to 1/3 density, Ruppia proliferates

•Ruppia does poorly in warm water but grows faster than Zostera, especially without competition•Zostera does not persist over winter.•Both species provide trophic support

Increased Precipitation

•Decreased soil salinity and increased water content - increase plant growth in many wetlands•Changes in animal composition and zonation dependent on salinity tolerance•damage from storms, flooding.•Grass zonation affected by changing salinities.

Eutrophication

Current Seagrass Paradigm:Nutrient overload -- epiphyte growth -- seagrass decline(=bottom-up control)

Alternative: Trophic Cascades with top down controlTop predator removal ---small predators increase ---Mesograzers decline (peracarids, shrimp, gastropods, pinfish)--

Epiphytes bloom --- seagrass declines

Ken Heck - 2003 ERF Meeting

Freshwater Export/Regime Shift•Striped Bass introduced to SF Bay from Hudson R. in 1879. •used as an indicator of environmental health.•Decline of Striped Bass in 1977and Delta smelt in 1982 attributed to water exports. (smelt listed as threatened).

BUT Bill Bennet proposes there was a behavioral response towarmer ocean water. Older individuals migrated to ocean.

(ERF 2003)

UV Damage - Bridgham et al.•Attenuation of UV radiation is an exponential function of dissolved organic matter (DOM) concentration

•UV-B penetration in darkly stained waters is limited to only a few cm.

•The strongest correlate of DOM concentrations in aquatic ecosystems is the percentage of wetlands in the watershed.

•Climate change may reduce DOM concentrations in aquatic ecosystems, thereby exacerbating UV effects, by changing the amount and flowpaths

of DOM from upland and wetland ecosystems.

Hypothesis: this linkage between wetland area and type, DOM, and climate will be the single most important factor determining the amount of UV damage to aquatic ecosystems at the landscape scale

RAMSAR Convention on Wetlands

The Convention on Wetlands, signed in Ramsar, Iran, in 1971, is an intergovernmental treaty which provides the framework for national action and international cooperation for the conservation and wise use of wetlands and their resources. There are presently 138 Contracting Parties to the Convention, with 1317 wetland sites, totaling 111 million hectares, designated for inclusion in the Ramsar List of Wetlands of International Importance.

Mission Statement: "The Convention's mission is the conservation and wise use of all wetlands through local, regional and national actions and international cooperation, as a contribution towards achieving sustainabledevelopment throughout the world" (Ramsar COP8, 2002).

Wetlands may store as much as 40% of global terrestrial carbon; peatlands and forested wetlands are particularly important carbon sinks.

Conversion to agricultural use and destruction of wetlands will release large quantities of carbon dioxide, the gas that accounts for at least 60% of the global warming effect.

As the full effects of global warming are felt over the next 100 years, the ability of coastal wetlands in some parts of the world to mitigate the effects of storm surges and other extreme weather effects will be put to the test; maintaining wetlands in a healthy state, avoiding further wetland losses and restoring and rehabilitating wetlands in the frontline of defences would be sensible tactics.

The ability of coastlines and coastal wetlands to "migrate" inland with sea-level rise is increasingly restricted through the infrastructure associated with human habitation in coastal areas – more than half the world’s population already lives in coastal zones and this proportion is increasing. Dense human habitation of coastal zones and intense economic activity will limit the capacity of some coastal wetlands to adapt quickly to sea level rise and more frequent storm surges.

RAMSAR Resolution VIII.3Climate change and wetlands: impacts,

adaptation, and mitigation

14. CALLS UPON Contracting Parties to manage wetlands so as to increase their resilience to climate change and extreme climatic events,and to reduce the risk of flooding and drought in vulnerable countries by, inter alia, promoting wetland and watershed protection and restoration;

15. CALLS UPON all relevant countries to take action to minimize the degradation, as well as promote restoration, and improve management practices of those peatlands and other wetland types that are significant carbon stores, or have the ability to sequester carbon and are considered as mitigation factors, as well as to increase the adaptive capacity of society to respond to the changes in these ecosystems due to climate change

Climate Change ConventionsJoint action between the UNFCCC (UN Framework Convention on Climate Change) and the Convention on Wetlands

i. Promoting linkages between the two Conventionsii. Predicting and monitoring the impacts of climate change on wetland areasiii. The role of wetlands in adapting to, and mitigating the impacts of, iv. climate changeiv. The role of wetlands in reducing greenhouse gas emissions.

The goal of these joint actions is to facilitate mutually supportive implementation of the UNFCCC and the Convention on Wetlands.

Issues to Ponder•To what aspects of climate change are southern Californiawetlands most vulnerable?

•Given susceptibilities to climate change, what conservation measures might you prioritize?

•How might elevated carbon dioxide levels affect the structureand function of southern California wetlands?

•How might climate change interact with other wetland stressorsof anthropogenic origin (e.g., eutrophication, pollutants,habitat loss, hydrologic alteration)?



Uncertain Future?

i. forms of climate change ii. long-term change iii. climate cycles iv. human- induced wetlands and...

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