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

THREATSEcological | Management | Social | Understanding or Attitudes | OrganizationalDESTRUCTIVE RESOURCE USE/EXTRACTIONThe use or extraction of a resource can beconsidered destructive if it severely disruptsnatural processes or species. This may cause morespecific threats discussed in the previous pages,such as over-exploitation of individual species,compaction of the soil or fragmentation of thelandscape.This section gives measures related to somecommon destructive resource uses or extractionactivities so that you can track what is often thesource of other threats to the ecosystem. For userelated to recreation, see p. 130.EXAMPLES OF DESTRUCTIVE RESOURCE USE/EXTRACTIONOver-grazing or over-browsing – can happen when animals feed excessively in a particular area,often completely consuming the vegetation, leading to soil erosion and significant threats to nativespecies (see also http://www.sierraclub.org/grazing/). Examples include some livestockoperations and over-browsing of hyper-abundant deer populations.Clear-cut logging – when all trees (usually > 1-2 inches in diameter) are harvested from an area,some simply to access to economically valuable species, reducing forest habitats and biodiversity.Destructive mining – when a large area of the land and vegetation covering a natural resource isstripped by bulldozers, power shovels, or stripping wheels, resulting in deep pits and “valley fills.”This can alter the flow of water, soil and nutrients, reducing habitat quality for many organisms,and in some cases, such as coal mining, lead to acid drainage.Cyanide bomb fishing – use of poison (potassium cyanide) to stun and capture valuable tropicalreef fish for aquariums and for “live fish” entrees at restaurants can damage coral reef habitat.Bottom-trawl fishing – large stern trawlers drag nets weighted with large, heavy, metal doorsacross the bottom of the ocean floor which alters the structure of sensitive benthic habitats.Sample evaluation questions and indicatorsX To what extent are the natural resource harvesting methods in our area destructive? Amount of sedimentation in rivers and streams near mining/clearcut areasNumber of fish kills downstream from mining/clearcut eventsArea of bare ground before and after tree harvestNumber of fish caught with ruptured bladdersNumber of dead coral polyps in fished areasAmount of by-catch or by-kill (non-target marine species harvest)Number and type of native plant species in grazed versus ungrazed areasExtent of soil erosion and/or compaction in grazed or logged areas (seeDisruption of soil p. 122)Ecosystem Management Initiative 128