Ecological applications of niche theory - Ecological Applications: Toward a Sustainable World - page 55

Niche theory
Conditions are physicochemical features of the environment such as temperature,
humidity and pH. Extreme conditions may be lethal, with a continuum of more
favorable values between the extremes, but species differ in their tolerance ranges.
Resources, in contrast to conditions, are consumed (e.g. photons by plants, plants
by herbivores). The fundamental niche defi nes the conditions and resources needed
by a species to practice its way of life. Because there are so many factors affecting
each species, the fundamental niche is multidimensional. Usually, a species has a
larger ecological niche in the absence of enemies (competitors, predators, parasites)
than in their presence. The realized niche describes the more limited spectrum of
conditions and resources that allow a species to persist even in the presence of
enemies.

Summary

Unwanted aliens
Managers need to differentiate among potential new invaders according to their
likelihood of establishing should they arrive in a new region. This is largely depend-
ent on their niche requirements. Managers increasingly use the process of ecological
niche modeling (generally of the fundamental niche), where occurrence patterns in
a species' native range are used to build a model that can be projected to identify
other areas that are potentially habitable. Habitat disturbance by human activities
may sometimes affect conditions or resources in a way that facilitates the success
of invaders.

Conservation of endangered species
Conservation may involve establishing protected areas or translocating individuals
to new, safer locations. Both approaches involve identifying geographical areas that
provide for the niche requirements of the species concerned. In the case of migratory
species, ecological niche modeling may be required at both ends of the migration
route, or at the end that is under particular threat. In cases where species' ranges
have shrunk to a tiny part of their original distribution, a misleading impression of
their fundamental niche may be gained - historical data may then be crucial.

Restoration of habitats
Land that has been damaged by mining is usually unstable, liable to erosion and
devoid of vegetation. Candidate plants for restoration are those that are tolerant of
the toxic heavy metals present - species, in other words, that have fundamental
niches incorporating the extreme conditions. Many plants characteristic of metal-
rich soils have evolved biochemical systems for nutrient acquisition and detoxifi ca-
tion. Managers can turn to phytoremediation , a process that involves introducing
such plants to contaminated soil, with the aim of reducing the concentrations of
heavy metals and other toxic chemicals.
Grasslands that have lost biodiversity because of intensive agriculture can be
restored (after reducing use of fertilizer/pesticide and/or grazing pressure) by rein-
troducing species with appropriate fundamental niches. The agricultural production
lost during restoration can be equated to the price of adding biodiversity (150-
200 euros per grassland species in one study).
One of the most pervasive of human infl uences on river ecosystems has been to
change patterns of discharge. River restoration often involves re-establishing