Humans in the Biosphere
A.Earth as an Island-
1. all organisms that live on Earth sharelimited resource base
2. Understanding how humans interact iscrucial to protecting resources
The iiwi (Hawaiian honeycreeper), anative species in Hawaii isbecoming scarce due to disease,habitat loss, and predation byintroduced species
1. Industry and Technology give humansadvantage in competing with other species forlimited resources such as food, energy, andspace
2. Today, humans most important source forenvironmental change
B. Human Activities
a. Hunting and Gathering-have changedenvironment since pre-historic times
Human hunters arrived in North America about12,000 years ago. They caused one of major massextinctions of large animals (woolly mammoths,giant ground sloths, saber tooth cats, cheetahs,zebras, etc.)
3). Green Revolution- global effort toincrease food production for fast-growing world population (new,intensive farming practices thatincrease yields)
C.Renewable and NonrenewableResources
a. Renewable- can regenerate (arereplaceable) not necessarily unlimited
b. nonrenewable- one that cannot bereplenished by natural processes (eg.Fossil fuels, oil and natural gas
1. Two types of environmental resources
2. Sustainable use- using natural resourcesso that you don’t deplete them (based onprinciples of ecology and economics)
3. Land Resources- provides space forcities, materials for industry, soils in whichcrops are grown.
desertification- in certain parts of theworld with dry climates, a combinationof farming, overgrazing, and droughthave turned once productive areasinto deserts
4. Forest Resources- provides products,habitats and food for organisms, moderatesclimate, limits soil erosion, protectsfreshwater supplies, “lungs” of the Earth”
deforestation- loss of forest. Canlead to severe erosion.Sustainable-use strategiesinclude selective harvestingand replanting.
5. Ocean Resources- provides valuablefood resources.
How do you explain graph #2 (fish catch perperson remains the same despite steadyincrease in world fish catch)?
6. Air Resources- Air is common resource.Preserving air quality remains a challenge formodern society.
a. Smog- common pollutant in largecities. (pollutant- harmful material thatcan enter the biosphere through land,air, or water)
b. Acid rain- acidic gasses releasedinto air and combine with water vaporforming drops of nitric and sulfuric acid.Can kill plants, change chemistry ofsoils and standing water ecosystems
Photomicrograph ofdrop of acid rain.Serious threat toenvironment
7. Water Resources- water is renewableresource but must be protected becausesupply is limited.
a. Water pollution- threatened bychemicals, domestic sewage, wastesdiscarded on land- all can seep intounderground water supplies.
City sewage must be treated insewage-treatment plants.Organic wastes are broken downby bacteria and then chemicalsare added to kill harmfulmicroorganisms.
D. Biodiversity- sum total of the geneticallybased variety of all organisms in thebiosphere
a. Ecosystem diversity- includes varietyof habitats, communities, and ecologicalprocesses in the living world
b. Species diversity- number of differentspecies in the biosphere
c. Genetic diversity- sum total of all thedifferent forms of genetic informationcarried by all living organisms
1. Forms of diversity
2. Biodiversity is one of Earth’sgreatest natural resources. Species ofmany kinds have provided us with foods,industrial products, medicines, etc.
3. Threats to Biodiversity-human activity can reducebiodiversity by alteringhabitats, hunting species toextinction, introducing toxiccompounds into food webs,and introducing foreignspecies into newenvironments
a. Pollution- many forms ofpollution can affect biodiversity.
Biological magnification-concentrations of harmfulsubstances increase inorganisms at higher trophiclevels. Affects all levels, buttop-level carnivore are athighest risk
By what number is theconcentration of DDTmultiplied at each successivetrophic level?
b. Introduced Species- one of mostimportant threats. Introduced eitherintentionally or unintentionally theyhave destroyed habitats of speciesnative to those ecosystems.
Fire ants wereaccidentally importedfrom Brazil about 45years ago. Now found inSan Clemente
4. Conserving Biodiversity- manyconservation efforts focusing on entireecosystems as well as single species
D. Charting a Course for the Future- two majorconcerns
1. Ozone depletion- naturally occurringozone gas (20-50 km above Earth’ssurface) absorbs good deal of harmfulultraviolet radiation from sunlight before itreaches Earth’s surface.
a. Beginning in 1970’sscientists found evidenceshowing ozone “hole” overAntarctica
b. Problem caused bycompounds calledchlorofluorocarbons (CFCs)
(CFCs act as catalysts that enableUV light to break apart ozone
2. Global Warming- an increase in averagetemperature of the biosphere.
a. Hypothesize that humanactivities have added carbondioxide and other greenhousegasses (methane, H20) into theatmosphere
b. Scientific models suggestthat could cause polar ice capsto melt and raise sea level. Thiscould also cause more severeweather disturbances
D. The Value of a Healthy Biosphere
1. Human society dependson healthy, diverse, andproductive ecosystemsbecause of theenvironmental andeconomic benefits theyprovide
2. People need to makewise choices in use ofresources and disposal orrecycling of materials