Humans in the Biosphere

A Changing Landscape

• * Human activities change the flow of energy in an ecosystem and can reduce the ability of ecosystems to recycle nutrients. Some activities that have transformed the biosphere:– Hunting and gathering– Agriculture – domestication of animals, modernization of

practices – Green Revolution (farming practices that increased yields of rice, wheat, and other crops)

– Industry – machines and factories during 1800s – cities grow rapidly

– Urban development – spread of suburban communities to new lands

• All of this activity by humans has affected ecosystems

Renewable and Non-renewable Resources

• Renewable – can regenerate and are replaceable, but not necessarily unlimited

• Non-renewable – cannot be replenished by natural means (fossil fuels – coal, oil, gas, uranium)

• Sustainable Use – using natural resources at a rate that does not deplete them

• * Human activities affect the supply and quality of renewable resources, including resources such as land, forests, ocean resources, air, and water.

Renewable Resources

• There are several renewable resources available:– Land – Forest – Ocean– Air– Water

Renewable Resources (continued)

• Land Resources – soil – should be renewable if managed properly – plowing leads to increased rate of soil erosion – leads to desertification

Renewable Resources (continued)

• Forest Resources – lumber – should be renewable – selective cutting vs. clear cutting – deforestation = erosion

Renewable Resources (continued)

• Ocean Resources – commercial fishing – should be renewable – overfishing leads to stock collapse – Aquaculture (farming of aquatic ecosystems) an option or limiting fishing amounts

Renewable Resources (continued)

• Air Resources – air pollution – smog – asthma – acid rain, ozone depletion, global warming – all affect air as a renewable resource

Renewable Resources (continued)

• Water Resources – industrial pollution, domestic pollution, groundwater contamination– Need to protect water supply to keep it as a

renewable resource

Biodiversity

• * Biodiversity is the sum total of the genetically based variety of all organisms in the biosphere

• Three divisions of biodiversity– Ecosystem diversity– Species diversity– Genetic diversity

Ecosystem Diversity

• Ecosystem Diversity – variety of habitats, communities, ecological processes

Species Diversity

• Species Diversity – number of different species in biosphere

Insects

BacteriaFungi

Plants

Protists Other Animals

54.4%

4.2%

18%

3.4%0.3%

19.7%

Genetic Diversity

• Genetic Diversity – sum total of all the different forms of genetic information carried by all organisms

Biodiversity (continued)

• *****Biodiversity is one of Earth’s greatest natural resources. Biodiversity provides us with foods, industrial products, and medicines.*****

• * Human activity can reduce biodiversity by altering habitats, hunting species to extinction, introducing toxic compounds into food webs, and introducing foreign species to new environments.– Extinction and endangered species (possibly due to over-

hunting) – can destroy food webs/ecosystems– Development of land = habitat fragmentation (split ecosystem

into pieces) – less species can live here– Pollution - DDT – biological magnification – concentrations of a

harmful substance increases in organisms at higher trophic levels – can destroy food webs/ecosystems

– Introduced species – invasive species – transported/not native – crowd out native species, often killing native species

PollutionFish-Eating Birds

Magnification ofDDT Concentration

10,000,000

100,000

10,000

1,000,000

1

1000

LargeFish

Small Fish

Zooplankton

Producers

Water

Biodiversity (continued)

• Conservation efforts focus on protection of entire ecosystems as well as single species. This will ensure that the natural habitats and the interactions are preserved.

Charting a Course for the Future

• 2 major concerns: Thinning/Depletion of Ozone and Global Warming– Ozone Depletion – Ozone absorbs UV radiation –

“hole” in ozone layer = damaging UV radiation. Must limit CFCs which destroy ozone

– Global Warming – human activities vs. natural variations in climate (not sure which is the cause…must study more with models)

• Value of a Healthy Biosphere- recycle, energy conservation – will help maintain a healthy biosphere