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

Global Climate Change The sun’s light hits the earth as UV light. It is reflected back to space as IR light. UV light can get through the atmosphere. IR light gets trapped by greenhouse gases such as CO2 and CH4. This traps the heat energy around the planet, warming the Earth.

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 hole in ozone layer at 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.