Humans and the Environment Threats to Biodiversity

Biodiversity refers to the variety of species in a specific area. Most biologists are confident that there are at least 10 million species on Earth— and as many as 30 million. After about 200 years of cataloging, scientists have named and described fewer than 3 million species.

The simplest and most common measure of biodiversity is the number of different species that live in a certain area (pg 111) Tropical regions contain two-thirds of all land species on Earth. The richest places for biodiversity seems to be warm places:

Places of great biodiversity Tropical rainforest Coral reef and large tropical lakes.

Biodiversity is important. 1)Living things are interdependent. Animals could not exist without green plants. Many flowering plants could not exist without animals to pollinate them. Plants are dependent on decomposers that break down dead or decaying materials into nutrients they can absorb.

In a rain forest, a tree grows from nutrients released by decomposers. A sloth eats leaves of the tree. Moss grows on the back of a sloth. Thus living things can be niches for other living things.

Populations are adapted to live together in communities. Although ecologists have studied many complex relationships among organisms, many relationships are yet to be discovered.

2) Scientists do know that if a species is lost from an ecosystem, the loss may have consequences for other living things in the area.

An organism suffers when a plant or animal it feeds upon is removed permanently from a food chain or food web. A population may soon exceed the area’s carrying capacity if its predators are removed.

If the symbiotic relationships among organisms are broken due to the loss of one species, then the remaining species will also be affected.

3) Biodiversity can bring stability to an ecosystem. A pest could easily destroy all the corn in a farmer’s field, but it would be far more difficult for a single type of insect or disease to destroy all individuals of a plant species in a rain forest.

4) Humans depend on other organisms for their needs. Oxygen is supplied & carbon dioxide is removed from the air by diverse species of plants and algae living in a variety of ecosystems throughout the world.

5) Think of all the food products that people eat, yet only a few plant and animal species supply the major portion of food eaten by the human population. Biodiversity could help breeders produce additional food crops.

6) Biodiversity can be used to help improve people’s health. Living things supply the world pharmacies. Active chemical compounds in many manufactured drugs are usually first isolated in living things.

The Extinct and the Endangered. Species can become extinct if every last member disappears. It is a natural process --- natural background extinction occurs at a rate of about one species per year per one million species. However, the current rate is many times that. Scientists hypothesize that this may be due to needs of the expanding human population, habitat loss, and land exploitation.

A species is considered endangered when its numbers become so low that extinction is possible. (Pg 115) When a population of a species is likely to become endangered, it is said to be a threatened species.

Threats to Biodiversity: Habitat loss - rain forests cleared to create farmland and supply firewood. Much of the land soon becomes useless for farmland due to the lack of nutrients.

Habitat fragmentation is separation of the wilderness areas from other wilderness areas ----usually due to development of the land for human population. It increases extinction of local species, disrupts ecological processes, changes local climate, and contributes to the species migration. Habitats can become too small for finding food and mates.

Damage to habitats by pollution: Air, water and land pollution Acid precipitation is linked to deterioration of forests and lakes. Sulfur dioxide from coal- burning factories and nitrogen oxides from car exhaust combine with water vapor in the air to form acidic droplets.

This moisture leaches calcium, potassium, and other nutrients from the soil. It has been linked to degrading lake ecosystems.

Ozone layer depletion – less ozone in the atmosphere means that less UV radiation is blocked causing damage to living organisms. (pg 118) (CFCs – Chlorofluorocarbons – the enemy of ozone)

Global warming: Excess, manmade CO 2 pollution has been seen as contributing to global warming. CO 2 is a greenhouse gas that traps heat from escaping the Earth. Burning fossil fuels adds a great deal of CO 2 which scientists claim will raise global temperature and cause climate changes. This may have a disastrous effect on the populations of many organisms around the world.

Water pollution A variety of pollutants can affect aquatic life. Excess fertilizers and animal wastes are often carried by rain into streams and lakes. These nutrients causes the excessive growth of algae (algal blooms). The algae dies, sinks, decays, & removes O2 from the water. Silt from eroded soil can enter the water and clog fish gills. Detergents, heavy metals and industrial chemicals can cause death of aquatic organisms.

Land pollution Trash, solid wastes-cans, paper, plastics, metals, dirt and spoiled food are thrown away every day. The average American produces about 1.8 kg of solid waste daily. Billions of tons of solid waste are buried in landfills. Strict controls on the design, construction and placement of landfills are meant to reduce groundwater contamination.

Pesticides and other chemicals can lead to habitat degradation. DDT, a chemical used to control mosquitoes, found its way into the food chain in birds, insects, fish and other small animals. The DDT was passes on to animals that preyed upon these affected animals.

Bald eagles and peregrine falcons were found to lay eggs with shells that cracked easily, killing the chicks. This caused a sharp decline in their populations. DDT has been banned since 1972 in the U.S..

Invasion species or exotic species are those accidently introduced into an ecosystem. They can be a problem for native species. After the Erie canal was built, the sea lamprey found its way to the Great Lakes and totally eliminated certain fish species from some of the Great Lakes.