Ecological applications of niche theory - Ecological Applications: Toward a Sustainable World - page 49

the species became confi ned to a much narrower realized niche by people who
hunted them, mammalian invaders such as red deer ( Cervus elaphus scoticus ) that
compete with them for food, and stoats ( Mustella erminea ) that prey upon them. The
current distributions of species like takahe, which have been driven very close to
extinction, may provide misleading information about niche requirements. It is
probable that neither the Murchison Mountains nor offshore islands (with pasture
rather than tussock grasses) coincide with the optimal set of conditions and resources
of the takahe's fundamental niche. Historical reconstructions of the ranges of endan-
gered species can be expected to help managers identify the best sites for reserves.

2.4 Restoration of
habitats impacted by
human activities

The term 'restoration ecology' can be used, rather unhelpfully, to encompass almost
every aspect of applied ecology (recovery of overexploited fi sheries, removal of
invaders, revegetation of habitat corridors to assist endangered species, etc.)
(Or merod, 2003). I restr ict my discussion to restoration of landscapes and water-
scapes whose physical nature has been affected by human activities, dealing specifi -
cally with mining (Section 2.4.1), intensive agriculture (Sections 2.4.2, 2.4.3) and
water abstraction from rivers (Section 2.4.4).

2.4.1 Land
reclamation -
prospecting for
species to restore
mined sites

Land that has been damaged by mining is usually unstable, liable to erosion and
devoid of vegetation. The simplest solution to land reclamation is the re-establish-
ment of vegetation cover, because this will stabilize the surface, be visually attractive
and self-sustaining, and provide the basis for natural or assisted succession to a
more complex community (Bradshaw, 2002). Candidate plants for reclamation are
those that are tolerant of the toxic heavy metals present; such species are charac-
teristic of naturally metal-rich soils (e.g. Alyssum bertolonii in serpentine geological
regions in Italy) and have fundamental niches that incorporate the extreme
conditions.
Of particular value are ecotypes - different genotypes, within a species, that have
different fundamental niches - which have evolved resistance in mined areas.
Antonovics and Bradshaw (1970) were the fi rst to note how the intensity of selection
for tolerant genotypes changes abruptly at the edge of contaminated areas - popula-
tions on contaminated areas may differ sharply in their tolerance of heavy metals
over distances as small as 1.5 m (e.g. sweet vernal grass, Anthoxanthum odoratum ).
Against this background, metal-tolerant grass genotypes (or cultivars) have been
selected for commercial production in the UK for use on neutral-to-alkaline soils
contaminated by lead or zinc ( Festuca rubra cultivar 'Merlin'), acidic lead and zinc
wastes ( Agrostis capillaris cultivar 'Goginan') and acidic copper wastes ( A. capillaris
cultivar 'Parys') (Baker, 2002).
Since plants lack the ability to move, many species characteristic of metal-rich
soils have evolved biochemical systems for nutrient acquisition, detoxifi cation and
the control of local geochemical conditions - in effect, they help create the condi-
tions appropriate to their fundamental niche. Phytoremediation involves placing such
plants in contaminated soil with the aim of reducing the concentrations of heavy
metals and other toxic chemicals.
Phytoremediation can take a variety of forms (Susarla et al., 2002). Phytoaccumula-
tion occurs when the contaminant is taken up by the plants but is not degraded
rapidly or completely; these plants, such as the zinc-accumulating herb Thlaspi
caerulescens , are harvested to remove the contaminant and then replaced. Similarly,