Invasive predators, competitors, and pathogens threaten many species
• People have moved many species to regions outside their original range,
deliberately or accidentally.
• Some become invasive –they spread widely and become unduly abundant at
a cost to the native species of the region.
• Invasive plants can have many negative effects on ecosystems: while native
plants must devote considerable energy to defending themselves against the
native herbivores. The invasive plants typically have high rates of growth and
reproduction b/c they invest less energy in producing defensive compounds.
Invaders tend to take advantage of soil nutrients in ways native plants
Rapid climate change can cause species extinctions
• If the climate warms by only 1̊ C, the average temperature currently found at
any particular location in N. America today will be found 150km to the north.
• If the climate warms 2̊C to 5C, some species will need to shift their ranges by
as much as 500-800km within a single century.
• Conservation biologists cannot alter rates of global warming.
• Organisms that are able to disperse easily may be able shift their ranges are
rapidly as the climate changes, provides that appropriate habits exist in the
• If the earth’s surface warms as predicted, entirely new climates will develop,
and some existing climates will disappear.
• New climates are certain to develop at low elevations in the tropics b/c a
warming of 2̊ C would result in climates near sea level that are warmer than
those found anywhere in the humid tropics.
57.4 What Strategies Do Conservation Biologists Use?
• Use data, concepts, and tools from a variety of disciplines.
• Determine what factors are affecting species health and numbers; use that
information to devise a plan.
Protected areas preserve habitat and prevent overexploitation
• Establishing protected areas is an important component of efforts to preserve
biological diversity; they serve as nurseries from which individuals disperse
into exploited areas, replenishing damaged populations.
• How should we select the areas to be protected? Two important criteria are
the number of species living in an area (species richness) and the number of
• Norman Meyers identified a number of biodiversity “hotspots” of unusual
richness and endemism (occupy only 15.7 percent of the Earth’s land surface,
but are home to 77 percent of the Earth’s terrestrial vertebrate species). BUT
this concept does not represent all of the Earth’s biodiversity.
• World Wildlife Fun identified 200 ecoregions of great conservation importance
from which biologists can develop a conservation strategy involving a
detailed analysis of distributions of species and locations of special resources.
• Conservation biologists have analyzed distributions of mammals, birds,
reptiles, amphibians, and conifers and have identified 595 “centers of
imminent extinction.” These regions are concentrated in tropical forests, on
islands, and in mountainous regions. The sites harbour 794 species judged to
at risk of extinction. Degraded ecosystems can be restored
• If the cause of a species’ endangerment is modification (rather than loss of
habitat), preserving the species may require tha