Lesson 26: Biodiversity and Its Decline
In this lesson, we will learn how biodiversity is measured. We will then take a
look at biodiversity around the globe and the troubling trend towards less
biodiversity, and the resulting consequences.
Scientists use 2 measures to calculate biodiversity:
- the number of species
- a measure of how "even" species are
A habitat has low biodiversity if it only has one species. In this case, there
are few members of other species that might leave or die. Diversity is higher
when one species is not completely dominant. While 8.7 million species have
been identified, there are an estimated 6 million more species that have not
been named or properly identified.
Biodiversity varies by region. Some areas are richer in
biodiversity than others. Costa Rica, for example, which is less than half the
size of New York, contains 5% of the world's living species. Biodiversity
represents an amazing and diverse storehouse of biological wealth.
Biodiversity is declining in many parts of the world due to
overpopulation, clear cutting, pollution and climate change effects. In North
America, over 500 native species in the United States have gone extinct. This
includes 100 vertebrates or animals with spines. Species that depend on
freshwater habitats such as crayfish, fishes, amphibians and mussels are at the
greatest risk.
Species population is an important element of biodiversity along with the
species' existence. Populations of species occupy different habitats and
contribute to biological wealth as they provide goods and services important to
ecosystems.
Birds lead the category of all species at the highest risk of extinction,
followed by amphibians, mammals and reptiles in an extensive report published
by the UN in 2010. HIPPO is the term used to describe the five factors that
contribute to decline in biological diversity.
These 5 factors are:
- habitat destruction
- invasive species
- pollution
- overpopulation
- overexploitation
Both Asia and Africa have lost almost two thirds of their original habitats,
leading to dramatic loss of biodiversity and changes in climate. Habitat change
has occurred largely due to conversion of areas into farms, housing, shopping
areas, malls, industrial centers and marinas. Small habitats have quickly
disappeared under the onslaught of human development that breaks up natural
areas, resulting in a mosaic of different habitats that no longer support prior
species. This is called fragmentation. Invasive species come from foreign areas
and decimate local populations of food and other competitors in the space. An
example is the black rat that came from Europe where it caused the plague, and
has been deadly to birds. Rats also eat crops, destroy property and cause other
harm to humans. Pollution directly kills both plants and animals. It can also
spread disease.
Human population growth has exploded in the past fifty to sixty years and has
led to overconsumption of natural resources and lands, destroying habitats and
also wildlife. Overexploitation occurs when people consume too many natural
resources without giving them time to replenish and thus decimate areas and all
life in the area. This happens as a result of greed, ignorance and desperation.
Also, illegal trade of wildlife is a destructive trade with poachers getting
over $12 billion in income illegally, right after drugs and guns.
What are the consequences of losing biodiversity?
Losing species is not only a moral issue but has serious effects on human life
- food, fuel, fiber and ecosystem integrity.
Natural ecosystems are
essential for human life. Forests and coral reefs also act as buffers against
storms and floods.
If the loss of biological diversity continues unabated,
the natural world as we know it will be far different. It will be a lot less
beautiful and varied.
Moving forward, education, conservation efforts and
public policy make the difference.