DECREASING POPULATIONS AND EXTINCTION
- When the population of an indicator species diminishes, the simplest reason is that its habitat is being negatively affected.
What is responsible?
- Often it is a complex accumulation of effects related to human development. We drain swamps and clear woodlands. We build roads that crisscross the countryside. We develop industries that release a huge range of chemicals.
- Some liquids are responsible for water pollution.
- Certain gases cause air pollution. Still other gases are linked to climate changes and endangering the protective layer of ozone encircling the Earth.
Q. Amphibians have delicate, heat sensitive, moist skin through which gases can easily pass. How would the effects of human activity listed above affect a frog's health?
The continued loss of population leads to extinction
Extinctions are both natural and manmade.
Natural extinctionsin the past have been dramatic, sometimes with about an 80% wipe out of species.
- A common hypothesis about the disappearance of the dinosaurs is that an asteroid crashed into Earth, causing huge tidal waves, earthquakes and fires. Dust from the impact and from fires would blot out the sun for years - temperatures would plummet and plants would die off. Soon, so would most animals in the food chains.
Humans and their activitiesare the major cause of extinctions.
- Some predictions suggest that each half hour, another species becomes extinct.
- A major irony in this whole thing is the loss of species we have not even discovered, especially in sections of rain forest being destroyed for land development.
- Who knows what new medicinal cures may be lost because the plant whose bark or flower or root contained a special chemical has been cut down and burned.