Human Impact On the Earth

Pollution

DDT (dichloro diphenyl trichloro ethane)

Starting in the 1940's, the chlorinated hydrocarbon DDT was used in vast quantities all over the world for killing insects. It was cheaper and much more effective than other insecticides against nearly all insects. It saved millions of lives by killing the mosquitoes that spread malaria and saved millions from starvation by killing crop pests..
But: in the 1950's and 1960's there was an alarming decline in the populations of several predatory birds, particularly fish-eaters such as bald eagles, cormorants, ospreys and brown pelicans.

DDT is toxic at high levels; but at lower levels it interferes with calcium deposition in eggshells, causing them to be thin, fragile, and often crushed by the parents in the nest.

Although DDT was suspected, the levels to which the birds had been exposed were nowhere near high enough to have killed them. But when the bird's bodies were analyzed, they were found to have up to one million times the concentration that was present in the sprayed water. This led to the discovery of bioaccumulation (also known as biological magnification), which means the steady increase in concentration of a contaminant with increasing level in the food chain. In the case of DDT, it results from the following factors:

1. DDT is not metabolized, and does not break down in the body.
2. It is much more soluble in fat than in water. So it accumulates in body fat and is not excreted.
3. The transfer of energy from lower trophic levels to higher ones is inefficient -so herbivores eat large quantities of plant material, and carnivores eat many times their body weight of prey during their lifetime. Since DDT is not excreted, the carnivore accumulates most of the DDT that was present in all of the prey organisms.

AIR POLLUTION AND ACID RAIN

Each year the U.S. discharges into the atmosphere:
15 million tons sulfur dioxide:
70% from power plants burning coal or oil.
30% from smelters and refineries.
20 million tons nitrogen oxides:
40% from cars, trucks, planes
30% from power plants
30% from other industrial sources.

Sulfur dioxide and nitrogen oxides combine with water in the air to form sulfuric acid and nitric acid, causing acid rain, Acid rain destroys plants and animals in several different ways:
1. Acidification of lakes directly kills algae, invertebrates, amphibians, and ultimately fish. The result is a crystal clear lake that is beautiful but dead
2. Removal of soil nutrients. Acid rain dissolves essential nutrients, including calcium and potassium, out of the soil thus reducing their availability to plants. It also kills microorganisms, preventing decomposition from returning nutrients to the soil.
3. Dissolving toxic metals. Acid rain also dissolves toxic metals, such as aluminum and mercury, which are otherwise insoluble and harmless.

CLIMATE CHANGE
The earth's climate may be warming as a result of the accumulation of "greenhouse gases", notably carbon dioxide. The kinds of data supporting this conclusion are.

Record breaking daily temperatures
Heat waves
Rise in sea level
Retreat of glaciers
Icebergs breaking of Antarctica
Early thaws
Increased rain and snow falls

*Many scientists feel that this is not enough data (over too small of a time period) to judge

LOSS OF BIODIVERSITY (Extinctions)

Habitat Loss **
Pollution
Overexploitation
International Trade (Poaching)
Disease
Introduction of Exotic Species

THE U.S. ENVIRONMENTAL PROTECTION AGENCY (EPA)

EPA's purpose is to ensure that:

• All Americans are protected from significant risks to human health and the environment where they live, learn and work.
• National efforts to reduce environmental risk are based on the best available scientific information.
• Federal laws protecting human health and the environment are enforced fairly and effectively.
• All parts of society-communities, individuals, business, state and local governments, tribal governments-have access to accurate information sufficient to effectively participate in managing human health and environmental risks.
• Environmental protection contributes to making our communities and ecosystems diverse, sustainable and economically productive.
• The United States plays a leadership role in working with other nations to protect the global environment.

**Some people feel the EPA is not doing what it was intended to do. That, the EPA often finds itself in conflict with landowners, towns, and individuals --> Remeber the Stossel Report on the Lead in Aspen?

The EPA's Pesticide Program

Over 20,000 pesticide products have been registered for use in the United States.
EPA is responsible for regulating the sale and use of pesticides, and the allowable levels in or on food.
EPA is responsible for registering, or licensing pesticide products - based on assessment of the potential effects on human health and the environment, when used according to label directions.

EPA's Strategy for Persistent, Bioaccumulative and Toxic pollutants (PBT) :

When a company or individual introduces a new chemical or a significant new use of a chemical, they must obtain a permit from the EPA. Tests include:
biodegradability in a single-organism test
biodegradability in a laboratory microcosm
bioaccumulation potential
chronic toxicity to fish (rainbow trout) and daphnids

CITES

International trade puts enormous economic pressure on suppliers and threatens the existence of many rare plants and animals. For this reason in 1975 the U.S., along with nine other countries, signed the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). The objective of CITES, which now involves over 150 countries, is to ensure that trade will not cause the extinction of plant or animal species.
CITES maintains lists of threatened species and regulates the import and export of those species.

Examples of animals on CITES lists: Great apes, Great whales, African elephant, All rhinoceros species, Giant Panda, sea turtles, crocodilians, Large cats, Several orchids, cacti and cycads

The U.S. Endangered Species Act of 1973 (ESA)

Unlike previous legislation, the act was not designed to protect only those species that were economically useful or potentially useful to man; it is based on the idea that species are of "aesthetic, ecological, educational, historical, recreational and scientific value to the nation and its people". The ultimate purpose of the Endangered Species Act is to bring about the recovery of endangered and threatened species. The Supreme Court has interpreted the act to mean that the value of species cannot be calculated, and that listed species should be protected whatever the cost. The ESA requires the following:

• It requires the Secretary of the Interior (through the U.S. Fish and Wildlife Service or, for marine species, the National Marine Fisheries Service) to identify and publish lists of species that are endangered (in imminent danger of going extinct) or threatened (likely to become endangered in the foreseeable future).
• A decision whether to list must be based solely on the biological evidence; economic factors are not relevant at this stage. Anybody that can provide adequate evidence can make a proposal for listing.
• Endangered species are given full legal protection against exploitation: they cannot be "taken ". "Take" means harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect, or to attempt to engage in such conduct. Such activities directed against animals are illegal even on private land.
• The federal government is prohibited from engaging in activities that could jeopardize the continued existence of listed species or adversely affect their designated critical habitat.
• A recovery plan must be developed and the recovery of the species must be monitored.
• The species or its products cannot be exported or imported.
  

Criticisms of the ESA
1. It doesn't help endangered species
2. It makes enemies of landowners
3. Species listing becomes political
4. It interferes with human (and homeowners) rights
5. It damages the economy

Animal Welfare Act

Requires that animals have:
proper and sufficient food and water
adequate shelter
the opportunity to display normal patterns of behavior
physical handling in a way which minimizes the likelihood of unreasonable or unnecessary pain or distress
protection from, and rapid diagnosis of, any significant injury or disease.
Act covers: pet stores, research, hunting, pets, zoos, circuses

Clean Air Act
The 1990 Clean Air Act is a federal law covering the entire country; states do much of the enforcement. For example, a state air pollution agency holds a hearing on a permit application by a power or chemical plant or fines a company for violating air pollution limits.
Under this law, EPA sets limits on how much of a pollutant can be in the air anywhere in the United States. This ensures that all Americans have the same basic health and environmental protections. The law allows individual states to have stronger pollution controls, but states are not allowed to have weaker pollution controls than those set for the whole country.