Evaluation Sourcebook (.pdf) - School of Natural Resources and ...

THREATSEcological | Management | Social | Understanding or Attitudes | OrganizationalEcological threatsHABITAT DEGRADATION, LOSS ORFRAGMENTATIONEcological communities or habitats aredegraded or lost if they no longer support thelevel of biodiversity or ecosystem functionthat is natural or characteristic for that area.For example, a forest community can bedegraded by the use of heavy machinery oroff-trail biking, because these activities leadto a loss of species and/or soil and waterquality. A habitat can be lost if it is not only degraded, but more fully changed, such as aforest being converted into monoculture farmland or a heavily-paved development.Habitat fragmentation goes hand in hand with both habitat degradation and loss.Fragmentation occurs when previously continuous habitat is converted into smaller andseparated pieces or fragments of habitat. It can also be the result of added infrastructure(roads, power lines, fences or dams). Fragmentation is a threat to ecological integrity notonly because it reduces the total amount of available habitat (directly and by creating lowqualityfragment “edge” habitat), but also because it prevents or hinders species interactionsand movement. The result is often a slow to rapid loss of the species that were found in theoriginal habitat.Measuring changes in the extent and severity of habitat degradation, loss andfragmentation and the factors causing this change can be a powerful measure of projectprogress.Sample evaluation questions and indicatorsX To what extent are we fragmenting the landscape?At what rate are natural areas converted to other uses? What is the rate of loss ofnatural areas? Change in land use or cover, including:Number of acres and rate of increase of developed land or sprawlNumber of acres grazedNumber of stream miles with vegetative coverPercent of land with impervious surface (paved, compacted, etc.)Percent loss of wetlandsRoad densityDifference in species composition (and other measures of habitat quality, p.32) between patches of interest and surrounding matrixX Are we reducing the level of habitat fragmentation? Average patch sizeNumber of patches in different size classesRatio of edge to interior areaEcosystem Management Initiative 110