Humans in the Biosphere Humans Affect the Biosphere

Humans in the Biosphere

Humans Affect the Biosphere in Four Major Ways: A. Global Climate Change B. Destroying the Ozone Layer C. Bioaccumulation D. Threatening Biodiversity

Our Global Climate • The sun’s light hits the earth as UV light. • It is reflected back to space as IR light. • IR light gets trapped by greenhouse gases such as CO 2 and CH 4. • This traps the heat energy around the planet, warming the Earth. • This “Greenhouse Effect” is a good thing, but the balance of gases is changing.

Sources of greenhouse gases (U. S. 2012)

Common Effects of Global Warming

The Ozone Layer • The ozone layer protects us from UV light. • UV light causes cancer, eye damage, and can damage plant tissue.

The South Pole

What Destroys the Ozone Layer? • Chlorofluorocarbons (CFC’s) are broken apart by UV light. This causes a chain of chemical reactions that results in ozone being broken apart. • CFC’s were used in aerosol cans, and as coolants in freezers and air conditioners. They are now banned in most countries.

Bioaccumulation (a. k. a. Biological Magnification) • Bioaccumulation is when pesticides and other toxins build up in animal tissue as you move up a food chain.

Bioaccumulation

DDT in Borneo • DDT was used on the Indonesian island of Borneo to kill mosquitoes. Lizards ate the mosquitoes. Cats ate the lizards. Cats began dying. • With no cats, the rat population grew. • Rats began spreading disease. • The government came up with a very interesting solution…. .

Parachuting Cats

DDT in the United States • DDT was used to kill mosquitoes. • DDT bioaccumulated and was found in high levels in the bald eagle. • DDT caused the birds to lay eggs with very thin shells and lots of pores. • When the parent birds sat on the eggs, the eggs broke. • Your national bird almost became extinct!

• DDT is still in the environment, despite the fact the last time it was sprayed was over 20 years ago.

Threatening Biodiversity • • Introducing non-native species Hunting organisms to extinction Introducing toxins Habitat destruction

Why is biodiversity important?

• At least 40 per cent of the world’s economy and 80 per cent of the needs of the poor are derived from biological resources. • The richer the diversity of life, the greater the opportunity for medical discoveries, economic development, and adaptive responses to climate change.

Medicines come from nature • We get digitalis, a very common heart medication, from the foxglove plant.

Human use.

Genetic diversity in crops • Most crop plants have wild relatives with useful traits. • We can visit this “library” when we need genes to improve our crop plants.

Ecosystems are more stable Ecosystems with more organisms are more stable.