Chapter 12Human Impacts upon Earth• Historical Basis of Pollution• Pollution: Human released products in the

amounts and durations that cause adverse effects.• Two primary factors that affect damage done

– technological “inventions”– population size 

• Biodegradable– Easily broken down into simpler compounds

• Non-biodegradable– Won’t break down or break down very slowly

Chapter 12• Population size: wastes produced faster than ecosystem

could dispose.– Sewage

• Urban centers enhanced this problem. 

• Eliminate “misery and disease”: often causes other problems.

 • Pesticides. • Often, pollution is in the eye of the beholder.

– Uranium ore – arsenic in water

Chapter 12Renewable and Nonrenewable Resources• Natural Resources: things usable by humans, but

which cannot be “created” by humans.• limited and unlimited• intensive exploitation moves unlimited to limited

resources.

 • renewable• vs. “natural• nonrenewable processes”

Chapter 12Mineral Resources—non-renewable• Locations of mineral resources is not based on

political boundaries• international trade required to bring in all types

needed• (U.S. & Canada has about 5.2% of world’s

population, and consumes about 30% of mineral resources.)

• Costs– Economic Costs ($$ to exploit resource)

– Energy Costs (to do the exploiting)

– Environmental Costs (pollution, habitat loss etc)

Chapter 12Steps : each step has costs•  Exploration

– time & technology– some energy– some environmental– becomes more intense as “easy” resources are consumed.

• Mining– Labor – Equipment – Energy (large costs)– Environmental (significant)

• mine tailings• water pollution & erosion• land disturbance

Chapter 12Refining (often part of mining)

– labor– equipment– energy– environmental

• air pollution• water pollution

Transportation– energy– some environmental

Manufacturing– labor– equipment– energy– environmental

Chapter 12Recycling• Can save significant costs by using materials which

do not require all of the above steps. 

• As energy costs go up, recycling will become more common. 

• Many pay the environmental costs, rather than the few who use a product.

• H/W must be able to collect easily and must have high economic value

Chapter 12Pristine Areas• Remote areas with harsh conditions are typically

pristine (e.g. arctic poles, mountain tops, open ocean)– Areas that won’t support agriculture.– Won’t support dense human population

• Other areas which until recently have been unaffected are being impacted.– will support limited agriculture or other human uses.

 • As human population grows.....

Chapter 12

• Many “parks” and protected areas have been designated as pristine areas become more rare.

 • “Wilderness” areas: where humans are visitors,

and do not remain. (U.S. definition)

• Parks becoming more noticeable in Africa, C/S/N America, Australia– Until recently had large amount of relatively untouched

land, now trying to preserve it

Chapter 12Modifications by Humans

About 40% of world’s land surface converted to cropland and permanent pasture.

Forest• Originally, 1/2 of U.S., 3/4 of Canada, 9/10 of

Europe, and much of rest of world.• Very large demand for wood.• Sustained yield: harvest rate equals rate of regrowth.

• Tropical forests are currently treated as nonrenewable resource, with extremely fast rate of depletion

Chapter 12

Forests reduce energy in rainfall, and practically stop erosion by slowing runoff.– Water is “evapo-transpirated” in large volumes.

– Shade and humidity moderate temperature extremes.

Tropical forests trap much CO2 but are in areas

of highest population growth pressures.

Chapter 12Management of forests require a compromise

between economic forces and environmental viewpoints.– Clear-cutting– Patchwork clear-cutting– Selective harvesting– Reforestation

•  Different species need different things in a forest (e.g. Red-Cockaded Woodpecker)

Chapter 12

• Deciding what to do with a forest requires a conscious decision:– known value of world’s forests– can assign value to wildlife and water within– Wilderness value is very difficult to

determine .... and forest can not be both an economic resource and a wilderness area.

• Have to choose in some cases or find way to satisfy both sides of issue

Chapter 12Rangelands • Arid and semiarid lands that can’t support typical

agriculture, but can support some grazing animals. • Grazing animals selectively reduce some plant species

(and inadvertently encourage others). Managers do the same. 

• Most grazing animals which are herded are “exotic” species, and reduce native species.

• Population pressures force people to graze too many animals (Tragedy of the Commons), remove trees for wood (nutrient removal) and push land towards “desertification”.

Chapter 12Aquatic Systems• Large areas of the ocean are still considered

pristine.• Most productive areas in the oceans are close to

shore:– nutrients/sunlight/ offshore currents bring nutrients up

from bottom– Concentrates pressure

• Fishing selectively removes some species. • Methods for catching bottom dwellers disturbs

habitat and wastes 25% of fish caught

Chapter 12• Most freshwater systems have been altered by

humans.– water quality changes– exotic species– thermal pollution

 • Many systems are manipulated to enhance some

desirable species.– Recreational and commercial interests

• Difficult to predict all the consequences of managing large natural systems.

• Difficult to manage all inputs to lake that may affect ecosystem

Chapter 12Wildlife Management• Improving conditions for species desirable to

humans. Manipulate one of the following: • -food and water• -cover (shelter):

– -escape from competitors

– -protection from weather

– -resting and sleeping

– -mating and raising young

• Quail

Chapter 12

• Must understand niche very well before attempting “habitat management”.

 

• Trying to improve the habitat for one species often harms the habitat of another.– Difficult role to try and take over mgmt of

 

• Migrating species require special considerations.

Chapter 12Natural Selection and Extinction• Extinction: elimination of all individuals of a

particular species (local and global). • Natural phenomenon .... estimated that only about 1

or 2% of all species which have existed are still alive today.

 • Speciation: appearance of a new species.

• Since things change, a species must adapt or become extinct.

Chapter 12

Extinction happens more often when: 

• species has small population/low reproduction rate

• dispersed individuals

• species occurs in small, restricted areas

• species is very specialized

Chapter 12Accelerated Extinction• Humans are among the most successful species currently

on earth:– adaptable– Intelligent– high reproductive capability– few enemies

As human population grows:– other species displaced (habitat alteration)– species utilized as food– used as ornaments– used for medicine– eliminated as pests

=accelerated extinction

Chapter 12Why worry? • Many species may be useful to us.

– food & medicine

 • Certain species play key roles in the ecosystems that

we utilize. • Most people find nature beautiful, and

“monocultures” are found disturbingly sterile. • Do all species have a fundamental right to exist?

Chapter 12Actions:• Protection of “threatened” and “endangered” species. • More action in developed nations than in less developed

nations. • Bias in protecting certain types of species:

– birds– mammals– butterflies– a few mollusks, fish and plants

Chapter 12World Conservation Union (former International Union

for the Conservation of Nature) Work (without much power, but much prestige) around

the world, especially in less developed nations.

U.S. Endangered Species Act (1973) • Attempts to protect threatened and endangered

species from governmental actions.• Political amendments and effects

– Endangered Species Review Committee• Can sanction extinction if economic benefits warrant

– Weakened ability to add species to list