The Biological

Foundation

of Critical Habitat

for Species at Risk

A Literature Review

Loggerhead Shrikeastrobirdphoto.com

Definition of Habitat• “The resources and

conditions present in an area that produce occupancy – including survival and reproduction – of a given organism.” (Hall et al. 1997)

• “The area or type of site where an individual or wildlife species naturally occurs or depends on directly or indirectly in order to carry out its life processes, or formerly occurred and has the potential to be reintroduced.” (Species At Risk Act 2003)

Grassland lbap.org.uk

Wetland eitangrunwald.com

Sagebrush tarleton.edu

Critical Habitat Definition• “The habitat that is necessary for the

survival or recovery of a listed wildlife species and that is identified as the species’ critical habitat in the recovery strategy or in an action plan for the species.” (SARA 2003)

Northern Spotted Owl commondreams.org

Old Growth Temperate Rain

Forestkathleenwelker.com

Criteria for Characterising Critical Habitat• Life History Requirements

– Primary biological needs• Shelter, food, reproduction,

dispersal, roosting, molting, metamorphosis, hibernation, migration etc.

– Variability• Temporal or demographic

Leopard frog Environment Canada

Pallid bat Texas Parks and Wildlife

Eastern Massasauga chicagoherp.org

Eastern Soft Shell Turtle carolinian.org

Community and Ecosystem Considerations

• Species interactions and ecological processes– Co-evolved obligate relationships– Disturbance dynamics

Small white lady slipperChicago Wilderness

Magazine

Soapweed naturephotographers.net

Yucca mothwildphotosphotography.com

Piping ploverIowa Dept. of Agriculture

Future Shifts in Habitats ~ Climate Change

• Distributions shifting to higher elevations and latitudes as global warming increases

Garry Oak Ecosystem Recovery Teamwww.goert.ca

Population-Level Requirements ~ Landscape Ecology

Fig. 1: Patch Size and Shape (Barnes 2000) ca.uky.eduFig. 3: Matrix quality and edge effects (Betts 2000, after Baskent and Jordan 1995) unbf.ca

• Minimum habitat amount (MHA) ~ Amount of suitable habitat necessary for long-term viability of a population.– Depends on species characteristics and requirements– Affected by size and shape of habitat patches– MHA increases as fragmentation increases– MHA increases as matrix quality decreases

Fig 2: Fragmentation (Barnes 2000) ca.uky.edu

Area Sensitivity

Hazel dormouse Encyclopaedia Brittanica

American Martencommons.wikimedia.org

• Levels of tolerance to habitat fragmentation and decreasing patch size– Individual-level response with population-level effects– Expressed in population density or nesting success

Henslow’s Sparrowindianaaudobon.org

Greater Prairie Chickenchickendancetrail.com

Margin for Error and Flexibility

• Patch size ~ bigger is better• Buffers ~ protective surrounding areas• Redundancy ~ more is better

• Emergency habitats ~

provide temporary refuges

Florida Snail Kitenaturescapes.net

Landscape-scale Considerations• Matrix quality ~ Improving the landscape mosaic

• Landscape connectivity ~ Movement between patches

• Habitat configuration ~ Spatial arrangement of patches

• Landscape complementation ~ Linking different habitats

http://www.biodiversitypartners.org/habconser/cnd/principles.shtml

Management Implications• Obtain as much species-specific

information as possible to determine critical habitat

• Consider requirements of individuals, populations, and all life stages

• Include matrix and landscape-scale effects on critical habitat and populations of species at risk

• Critical habitat designation must be adaptive, continuously adjusting to new information about a species

Criticism and Additional Literature

• “How Useful Is The Concept Of Habitat? – A Critique” (Mitchell 2005)– May be many more factors than habitat determining the

viability of a population or species

• “Habitat, Environment and Niche – What Are We Modelling?” (Kearney 2006)– Knowledge of how a species interacts with various aspects

of its environment is crucial in understanding its distribution and abundance

• “Habitat Restoration – Do We Know What We’re Doing?” (Miller, Hobbs 2007)– No “one size fits all” approach, must balance species

requirements with various constraints on restoration work

• Wildlife-Habitat Relationships, Concepts and Applications (Morrison, et al 2006)– From evolutionary perspective to experimental approach

and analysis, with an emphasis on relationships and interactions between species and habitat

Literature Cited• Barnes, T.G. 2000. Landscape Ecology and Ecosystems Management.

University of Kentucky Cooperative Extension Service. Companion publication to FOR-75, "An Ecosystems Approach to Natural Resources Management"

• Betts, M. 2000. In Search of Ecological Relevancy: A Review of Landscape Fragmentation Metrics and Their Application for the Fundy Model Forest. Greater Fundy Ecosystem Research Group (GFERG), University of New Brunswick

• Kearney, M. 2006. Habitat, environment and niche: what are we modelling? Oikos 115:1 pp. 186-191

• Miller, J.R. and R.J. Hobbs. 2007 Habitat restoration – do we know what we’re doing? Restoration Ecology 15:3, pp. 382–390

• Mitchell, S.C. 2005. How useful is the concept of habitat? – A critique. Oikos 110:3 pp. 634-638

• Morrison, M.L., B.G. Marcot and R.W. Mannan. 2006. Wildlife-Habitat Relationships, Concepts and Applications. Island Press, Washington D.C.

• Vance, M. 2003. The biological foundation of critical habitat for species at risk: A literature review. Canadian Wildlife Services

Discussion Questions

• What kind of relationships between an organism and its environment are likely to be the most important to the protection of species at risk and their habitats, and why?

• What are the biggest conflicts involved in trying to balance the needs of a species at risk and its habitat with those of an expanding human population?