Issues in the Ecology of Highway Design and Construction

Population Ecology 121

For Highway Engineers, Designers, Planners, Biologists, Construction

Managers, and Equipment Operators

Population Ecology 121

• Population dynamics– N0 - number at time 0– Nt - number at time t– - r – rate of natural increase of a population– - r = b – d (birth minus death) per unit time– Nt = N0 e t[b-d]

• Where will you see r as a highway engineer?

Pop Dynamics

• - r selected species – selected for fast reproduction. High birth and death rates, very dynamic species – dynamic environments

• - k selected species – k is the density dependent limit in a population. Selected for survival and competition. Lower birth and death rates, more stable populations from generation to generation

• Survival rate = ?

Pop Dynamics

• Density dependent interactions

• Coefficients of competition [k dependent] - Compensatory responses – r species– -b goes up, d goes ?– Compensatory fecundity– - d goes up, b goes ?– What are the limiting factors?

Pop Dynamics

• K selected species – compensatory response

• - b goes up, d goes up

• - d goes down, b goes down

• Depensatory responses – The Dark Side

• density related– - b goes down, d stays the same, or increases– - d goes up, b goes down or stays the same

Pop Dynamics

• Environmental effects • Weather

– Seasonal or annual– Longer cycles

• Long term habitat alteration– Natural change – succession, fire– Man caused change

• Predators, invaders

Terminology

• Diversity – variability – kinds of diversity• Metapopulations – a group of local

populations; a regional population• Extinction - scales

– Random or Stochastic– catastrophes– Time integrated cumulative response

• Genetics - population– Genetic drift, genefixation

Terminology

• Examples of Phony terminology– META-ANALYSIS– FOCAL SPECIES– DIVERSITIFICATION– “r” values for small populations carried out to

three decimal places – example grizzly bears

Ecological Issues in Transportation

Connectivity, Fragmentation

And Dispersal

Dispersal

• Movement of individuals between habitats, populations, or landscape elements – tends to be random, forced, and non regular

• Versus migration – a regular movement of populations between seasonal habitats

• Maintains genetic diversity

• Maintains scattered local populations

Connectivity

• Integration of functional elements

• Stability– Species composition– Genetic composition

• Diversity and Distribution

• Maximizes Energy and Material Cycling

• Maintains Population densities

Connectivity

• Different Scales– Connections between habitat patches– Connections between landscapes [ecosystems]

• Considerations in mitigation and conservation measures– Off site banks versus on site spot mitigation

Connectivity

• Do we always want connectivity

• If not, Why not?– Artificial connections which introduce

invasives, exotics

• Well then, when– Maintain or restore natural interactions and

functional linkages

Fragmentation

• Fragmentation versus Connectivity – Opposite sides of the same coin

• Fragmentation – process of breaking down landscapes into smaller and smaller functioning elements

• Connectivity – characteristic of landscapes through which elements are connected or can interact

FragmentationCharacteristics

• Isolation of small or local populations from each other or habitat elements

• Creation of new edges and habitat types • Introduction of new species • Alteration of plant communities – invasives

– Can reduce habitat diversity– Eliminates or alters Niches– Response in other community elements

FragmentationOutcomes

• Changes in biological parameters of species populations– Birth rate – isolation from needed seasonal

habitat– Death rate – road kill a new mortality factor– competition, predation, disease– Genetic composition

• Reduced Species Diversity and Distribution

• Random population extinctions

How do we establish or maintain connectivity?

Aspect or Openess Ratio

• Is the ratio of area of the opening to length of the crossing structure

• Operational minimum of 2 in feet/yards• Varies with species• For ungulates height is important

– 8 feet minimum– Wyoming study showed 8x24x100 worked ok

for mule deer

Animal Responses

• Varies with species

• Some show learned behaviour

• Crossing rate varies with environmental pressure

• Fencing can be important

Structures

• Where do we put ‘em?– Avoid developing sites – can get isolated– Establish land use control if practicable– Look for natural connections– Constructability– Economy– Safety

Where do we put these things?

• Avoid areas of dynamic land use– Structures can be quickly isolated

• Select areas of critical need where environmental pressure to cross is high

• Design the structure to the species of primary concern, but multispecies designs are to be desired

• One size may not fit all

U. S. 93 Montana Ecosystem Approach

• OBJECTIVE: strategy and approach to Ecosystem based mitigation for the 93 corridor.

• Goals: – maximize the conservation benefits, – sustain ecosystem integrity, – timely implementation of planned highway

improvements.

Framework for an Ecosystem Approach

•  A method for assessing ecosystem impacts of transportation projects.

• A valuation system for determining conservation credits and debits when out of kind mitigation alternatives are preferred.

• An inventory and regional maps of habitat, land cover type and use in the region of concern.

Framework for an Ecosystem Approach

• An approach to identifying and prioritizing practicable conservation needs within the region of concern.

• An approach to determining reasonable costs for participation with transportation funds in ecosystem mitigation measures.

• Authority to exercise regulatory and administrative flexibility to achieve practicable, integrated conservation goals and needs based on ecosystem functions, values, and benefits.

Framework for an Ecosystem Approach

• An interagency group which will identify and recommend appropriate mitigation options based on regional and local conservation needs.

• Elevation authority so that administrative procedural roadblocks can be rapidly resolved.

Corridor Mitigation Concepts

The basic concepts of the Ecosystem based Corridor Mitigation Concept developed by the IRT include:

1. Integrated mitigation based on the definition of Ecologically Similar Areas (EcSA), defined by practical and functional boundaries.

2. Mitigation measures for impacts occurring in those areas would be prioritized toward location within the same EcSA, similar to the concept of a ecological mitigation bank’s service area.

Corridor Mitigation Concepts

• Aquatic and terrestrial mitigation addressed separately or concurrently, depending on agreed-to conservation objectives and regulatory/ administrative flexibility, as provided through appropriate agencies.

• Highest priority conservation needs within the EcSA.

• Flexibility to sustain ecosystem integrity, functions, and values.

• A consensus based steering group

Corridor Mitigation Concepts

• Integrated local and regional conservation planning– Forest Management Plans– the Montana State Habitat Conservation Plan,– Endangered species recovery plans, and – local, regional, and tribal conservation management

efforts.

• Local input and participation in defining and establishing conservation priorities and mitigation alternatives

TOOLS

• Available tools and information used to the maximum extent practicable.

• new tools or data developed on a consensus basis with shared funding and responsibilities

• The Statewide Habitat Conservation and Management Plan, which is required of each state to get federal wildlife funds. These plans will designate habitat conservation priorities for the State within specific ecoregions, based on habitat types, risks, and species conservation needs.

TOOLS

• State Regional Wildlife and Fisheries Management Plans

• Regional ecosystem linkage zone and habitat use models developed for specific species by the US Fish and Wildlife Service and cooperating agencies.

• The Corps of Engineers Mitigation Matrix developed for the Section 404 Regulatory Program. This matrix is compatible with the State Habitat Conservation plan.

TOOLS

• Other reports and plans, such as The Assessment of Wildlife and Fish Habitat Linkages on Highway 93 – Western Montana (Ruediger, Lloyd, et al, 2004, USFS report).– State Wildlife Agency Regional Management Plans.– Tribal conservation, wildlife, and habitat conservation

and management plans.– Forest Management Plans for wildlife and habitat

management.– Local land use and conservation plans, goals, and

objectives.

TOOLS

• The Critter Book - 2005• Performance Measures for Ecosystem

Management and Ecological Sustainability (The Wildlife Society, 2002).

• NAS report: Ecological Impacts of Road Density (due early 2005)

• NAS report: Valuing Ecosystem Service: Toward Better Environmental Decision Making

• Reports of the International Grizzly Bear Committee

CRITICAL NEEDS

1. An impact assessment approach for direct and cumulative ecosystem impacts and mitigation needs.

2. A method to value credits and debits so that mitigation will be appropriate to impacts

3. Procedures to enhance flexibility in regulatory programs at the field office level

4. An approach to rapid administrative elevation to resolve procedural roadblocks

Exemplary Ecosystem Initiatives

•Purpose: To identify and promote activities that can restore, enhance, and sustain natural systems and their functions and values, while continuing to meet safety and mobility needs.

Exemplary Ecosystem Goals

• Ecosystem/habitat conservation was chosen to measure environmental stewardship in FHWA’s Strategic goals because:– It focuses on specific contributions of federally-

funded highway projects to ecosystem conservation; – a particularly high and growing priority for

environmental review and regulatory agencies, environmental interest groups, and the public;

– provides highly visible examples of proactive environmental stewardship by transportation agencies;

Exemplary Ecosystem Initiatives

•Purpose: To identify and promote activities that can restore, enhance, and sustain natural systems and their functions and values, while continuing to meet safety and mobility needs.

Exemplary Ecosystem Initiatives

• Thirty examples of exemplary ecosystem initiatives in at least 20 states by 2007.

• Full information at http://www.fhwa.dot.gov/environment/ecoinitc.htm