Download Text – Threats to Biodiversity

African Wildlife – A wonder and a challenge
The Problem:
The Extinction Crisis: The human species, one of millions of life forms on this planet, is
threatening the very existence of many other species. Biological diversity, or biodiversity,
is the variety of life forms that interact to support and sustain the balance of nature.
Why it Matters: Should it matter to humans that other life forms are disappearing?
Many people think so. Human populations depend on plants and animals for much of
their food, medicines, clothing, and shelter. We also depend on plants for oxygen and
clean air.
Threatened and Endangered Species: A species or subspecies is regarded as
"endangered" when it is in danger of extinction throughout all or a significant part of its
normal range. In the last 500 years, human activity has forced over 800 species into
extinction, and there are currently 41,415 endangered species on the planet.
Examples - A Snapshot of Endangered Species of Africa:
Black Rhino - The black rhino has not fared so well. As recently as 1970, an estimated
65,000 black rhinos could be found throughout sub-Saharan Africa. But in eastern Africa,
90 percent of them were killed in the 1970s. Now there are fewer than 2,500 left, in
pockets in Zimbabwe, South Africa, Kenya, Namibia, and Tanzania.
Elephant - Demand for ivory, combined with habitat loss from human settlement, has led
to a dramatic decline in elephant populations in the last few decades. In 1930, there were
between 5 and 10 million African elephants. By 1979, there were 1.3 million.
Lemur - No comprehensive surveys have been done, but it is estimated that there may be
more than 10,000 black lemurs surviving in the wild. Black lemurs are limited to the
extreme northwestern tip of Madagascar and a few outlying islands.
Crocodile - The dwarf crocodile, at no more than 5 feet (1.5 m) long, is the smallest of 3
species of crocodile which occur in Africa. It is found in swamps and slow-moving
streams in the Tropical rain forests of West and Central Africa. The dwarf crocodile is
now regarded as rare throughout its range.
Turtle - The leatherback sea turtle is a circumglobal species, meaning that it can range
throughout almost all the oceans of the world. It nests on tropical beaches in the Atlantic,
Indian, and Pacific Oceans. Once abundant throughout the world's oceans, all eight
species of sea turtles are now threatened or endangered.
Causes - Factors Contributing to Loss of Biodiversity:
1. Habitat Loss: The most common cause of endangerment is habitat loss due to
urbanization and deforestation. Plants and animals need space to live and energy
provided by food, just as humans do. As human population and consumption
increase, wildlife habitat is converted to houses and highways. Forests are cut down
for building materials, fuel, and paper.
Plants and animals need space to live and energy provided by food, just as humans
do. As human population and consumption increase, wildlife habitat is converted to
houses and highways. Forests are cut down for building materials, fuel, and paper.
Prairies and forest land are turned into crop land and grazing land for our livestock,
and shopping malls stand where wetlands once existed. The damming of rivers to
create hydropower has flooded river valleys, making it hard for ocean-going fish to
migrate. Even if habitat is not completely destroyed, it can be fragmented or
degraded so much that it can no longer support the species it once did. Many
species, particularly large mammals, need large areas of habitat to survive and
reproduce. Patches of forest or grassland surrounded by farms or cities, or divided
by roads, will not support these species. (For more discussion of the effects of
fragmentation, see Island Biogeography).
2. Overexploitation: Humans also deplete wildlife populations by capturing or
killing individuals for their own use. Animals are killed for food, fur, feathers, oil,
medicines, crafts, and a host of other uses. Poachers kill animals such as elephants
because their ivory tusks are valuable. Animals are also shot to stop them from
killing livestock, or simply for sport. Humans also deplete wildlife populations by
capturing or killing individuals for their own use. Animals are killed for food, fur,
feathers, oil, medicines, crafts, and a host of other uses. They are also shot to stop
them from killing livestock, or simply for sport. Animal eggs are taken for food,
and species are captured for pets or to use in medical experiments. Sophisticated
technology allows ever-increasing numbers of animals to be captured at once,
depleting seemingly limitless species like ocean fish. As the developing nations of
the world accumulate more wealth, the demand for animal products grows. The
international market for animals and animal parts is a huge and growing cause of
wildlife endangerment.
3. Pollution: One of the ways habitat is degraded is by pollution. Pollution occurs as
a result of urbanization. Creatures that depend on either freshwater or saltwater for
all or part of their life cycles, like fish, frogs, marine mammals, and many
invertebrates, are especially vulnerable to pollution.
One of the ways habitat is degraded is by pollution. Creatures that depend on either
freshwater or saltwater for all or part of their life cycles, like fish, frogs, marine
mammals, and many invertebrates, are especially vulnerable to pollution.
Water is polluted by things like run-off of fertilizers and pesticides from farms, oil
and other chemicals from roads, and human sewage that flows untreated into rivers,
lakes, and oceans. In addition to polluting waterways, we divert fresh water from
rivers and lakes for irrigation, drinking water, and industrial uses. There is less
water left in the rivers and lakes to dilute the polluting chemicals. Ships pollute
saltwater by dumping waste. Oil spills kill large numbers of animals. Many smaller
spills and leaks go relatively undetected, but their cumulative effects over the years
also can injure wildlife.
Water is not the only element that suffers from pollution. Factories and cars release
chemicals into the air. The chemicals are deposited on land by rain, causing
pollution, including what is known as acid rain. Acid rain weakens and kills plant
life, decreasing the food supply for animals that eat the plants.
Pesticides are another source of pollution. Farmers use pesticides to keep insects
from eating crops. Pesticides remain in crops and in wild plants eaten by herbivores
(plant eaters). Insects also carry pesticides. Animals that eat herbivores (like
predatory birds) and insects (like birds and amphibians) get high concentrations of
these chemicals in their systems. The chemicals can disrupt physical functions like
reproduction in these animals.
Possible Solutions:
1. Conservation Biology: The new discipline of conservation biology has developed
to respond to the increased threats to biological diversity. Its main goals are to
determine human impacts on other species and to develop practical solutions to
reduce the extinction rate.
2. Conservation Actions: There are many ways conservation biologists are
addressing the extinction crisis. These include 1) Establishing protected areas
where wildlife habitat is preserved or restored 2) Developing new ways to farm,
log, and graze livestock, that preserve habitat values; and many more...
Questions for Thought:
Society does not have the resources to save every species from human-caused extinction.
How should we decide where to put our energy and resources in conserving species?
Should we concentrate on the species people like best? What other criteria might we
use?