8095

• UCREFRP Catalog Number: 8095
• Author: National Research Council.
• Title: Impacts of Emerging Agricultural Trends on Fish and Wildlife Habitat.
• USFW Year: 1982.
• USFW - Doc Type: Washington, D.C.
• Copyright Material: NO

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patterns of vegetation important to wildlife (Thomas 1979). It long
has been known that borders, or edges, between two vegetative types
are rich in number of species (diversity) and sometimes in numbers of
individuals of a species (abundance). Many contiguous different types
of vegetation and the edges between them form a horizontal pattern,
which is attractive to wildlife. vertical layering, such as in
forests, is another habitat pattern that induces use by a variety of
species, and this is regarded as beneficial to wildlife.
The habitat diversity of an area may be a result of natural,
local, climatically controlled vegetation, but it also is influenced
by time. Natural or man-made disturbances of vegetation induce a
succession, which begins with pioneering plants that are subsequently
replaced with change in microclimate and soil conditions, including
nutrient level and nutrient exchange. Different wildlife communities
have adapted to these various vegetative stages because of the
different food and cover available in each. Thus wildlife communities
are dynamic. In streams and lake~, similar processes occur that are
influenced by physical conditions, age, and nutrient level.
There are other general patterns in fish and wildlife
communities. In communities with few species, the species occupy
broad niches. In more complex communities with many species, the
niches are narrow (MacArthur and Wilson 1967). Essentially,
competition for resources induces specialization and reduces niche
breadth. A more complex vegetative structure then produces more
potential sites for animals with different requirements while it
reduces competition. Hence habitat diversity generally produces a
greater diversity of fish and wildlife.
Natural processes such as fire, flood, and grazing cause a
continuing plant successi?n, and hence wildlife diversity, in natural
systems. However, severe natural effects such as fire can decrease
wildlife diversity. The management practice of temporarily lowering
the water level in a marsh, known as drawdown, produces this effect
also. Management goals often include setting back succession to
stimulate and hold a particular plant community, such as quail habitat
management by fire or manageme.nt of an endangered species habitat in
which a reduced habitat would be further endangered by natural
succession toward local mature communities.

EFFECTS OF AGRICULTURAL ACTIVITIES ON WILDLIFE HABITAT

Agricultural activities on cropland, rangeland, pasture, and forest
land have been altering wildlife habitat, in both positive and
negative ways, throughout America's history. Agricultural and
forestry production has increased to meet the growing demands of an
expanding and more affluent population for food, fiber, and forest
products. During the early periods, the clearing of forests for
small, scattered farms created habitat diversity that provided a
fertile environment for species like robins, woodchucks, and bobwhite
quail. But, at the same time, it decreased favorable habitat for
other native populations, such as wild turkeys, black bears, and