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<br />OD25.~3 <br /> <br />Probable Effects that Each Alternative Will <br />Have on the White River National Forest <br /> <br />Biodiversity <br /> <br />Biodiversity is not static -- it fluctuates in response to ever-changing human and <br />environmental influences. The environment of the Forest today is not the same as it was <br />before western Colorado was settled by people of European origin. Nor is it the same as <br />it was during the early settlement period from 1870 to about 1900, when unregulated <br />resource exploitation was common. <br /> <br />One way to understand how the biodiversity of the White River National Forest has <br />changed is to examine the Forest's historic range of variability, or HRV. Revision of the <br />Forest Plan included a study of this range, which shows what ecological conditions were <br />present in the area before large-scale settlement began, as well as how these conditions <br />have changed since then. <br /> <br />Some conditions are essentially unchanged, while others have departed from earlier <br />norms. Some conditions have changed because such variability is natural for them. <br />These conditions can be said to be within their HRV. Other conditions have changed due <br />to human intervention to a point that they are not within the range of long-term fluctuation <br />(over the 200-400 year period before settlement) that is natural for them. These <br />conditions are considered to be outside their HRV. In short, the HRV represents the <br />Forest's baseline ecological conditions, to which we can compare current conditions and <br />better understand the effects of forest management activities. <br /> <br />Analysis of these conditions reveaied that most components of biodiversity on the Forest <br />are within their HRV, but some are not: <br /> <br />. Rangelands have been affected by the spread of noxious weeds and reseeding with <br />non-native species. These impacts are expected to continue in all alternatives. <br /> <br />. Some forest stands are outside of the HRV conditions because of management <br />activities, such as fire suppression and ski area development. Alternatives F, E and <br />B allocate the most acres to ski-based resorts; therefore, they will have the most <br />impact to HRV conditions within permit boundaries. Other management activities are <br />not expected to change HRV conditions significantly in any alternative. Fire <br />suppression is expected to remain at a comparable level in all alternatives. <br /> <br />. Alternatives D and C both stress the need to manage within HRV parameters, while <br />Alternatives Band F do not emphasize managing within the HRV. Impacts to HRV <br />conditions will be the most significant under Alternatives Band F. <br /> <br />Another way to assess the biodiversity of the Forest is to determine how wildlife habitats <br />have been affected by changes in forest and rangeland vegetation. Two key aspects of <br />how these habitats have changed are fragmentation and perforation. <br /> <br />. Fragmentation of wildlife habitat is defined as the breaking up of contiguous blocks <br />of habitat into progressively smaller patches that are increasingly isolated from one <br />another. It may also be viewed as the process of interspersing blocks of suitable <br />habitat within areas that are hostile to plant or animal life, such as highways or <br /> <br />-- 23 -- <br />