Unit 2 Ecology

Ch. 6 Humans in the Biosphere

Earth as an Island

Earth is an island, that all organisms, including humans, live on & share a limited resource base, & depend on for their long-term survival

We all rely on the natural ecological processes that sustain these resources

Earth as an Island

To protect these resources, we have to understand how humans interact with the biosphere

We must also learn how to predict what will happen in the future

Human Activities

Some human activities that affect the biosphere are hunting & gathering, agriculture, industry, & urban development

Human Activities

Hunting & Gathering:For most of human history, our ancestors

got food by hunting & gatheringToday, groups of people in different parts

of the world follow the hunter-gatherer way of life

As a result of overhunting, species have become extinct

Human Activities

Agriculture:Agriculture - the practice of farmingPeople in different regions grow wheat,

rice, & potatoesThe development of agriculture included

raising animals like sheep, goats, cows, pigs, etc.

Human Activities

Agriculture:Agriculture provides a stable & predictable

food supply for humansMonoculture - large fields are planted with

a single variety of crop, year after yearChemical fertilizers boosted plant growth &

pesticides controlled crop damaging insects

Human Activities

Agriculture:Green revolution - period of time in the

middle of the 20th century, when governments began a major push toward an increase in the world’s food supply

Over the last 50 years, the green revolution has helped world food production double

Human Activities

Agriculture:While increasing food supply, modern

agriculture has created ecological challenges

Chemical pesticides have contaminated water supplies, usable water has declined, etc.

Human Activities

Industrial Growth & Urban Development:Cities have greatly contributed to pollution

of air, water, & soilHuman wastes have been dumped into

habitats, polluting those habitats, etc.

Renewable & Nonrenewable Resources

Environmental goods & services may be either renewable or nonrenewable

Renewable resources - can be replenished by biochemical cycles if they are nonlivingEx.) Water is a renewable resource that

can become limited by drought or overuse

Renewable & Nonrenewable Resources

Nonrenewable resource - 1 that cannot be replenished by natural processesEx.) Fossil fuels like coal, oil, & natural gas

are nonrenewable resourcesFossil fuels formed millions of years ago

from deeply buried organic materialsWhen they are depleted, they are gone

forever

Renewable & Nonrenewable Resources

The classification of a resource as renewable or nonrenewable depends on its context

A single tree is renewable, but a population of trees in an ecosystem, may not be renewable because the ecosystem may change forever once those trees are gone

Sustainable Development

Human activities can affect the quality and supply of renewable resources like land, forests, fisheries, air, & fresh water

Sustainable development - a way of using natural resources without depleting them & of providing for human needs without causing long-term environmental harm

Land Resources

Land is a resource that provides space for human communities & raw materials for industry

It also includes the soils where crops are grown

If managed properly, it is a renewable resource, but could become nonrenew.

Land Resources

Plowing the land removes the roots that hold the soil in place, which increases soil erosion

Soil erosion - the wearing away of surface soil by water & wind

Land Resources

In dry climates, a combination of farming, overgrazing, & drought has turned once productive areas into deserts - Desertification

Forest Resources

Deforestation - loss of forestsIt can lead to severe erosion, can wash

away nutrients, grazing after deforestation can deplete nutrients permanently

Fishery Resources

Fishes & other animals that live in water are a valuable source of food for humanity

Overfishing, or harvesting fish faster than they can be replaced by reproduction, has greatly reduced the amount of fish in the ocean’s

Fishery Resources

People from several countries were taking advantage of a resource, fisheries

Until recently, fisheries seemed to be a renewable resource, that could be harvested indefinitely

Overfishing has destroyed that resource

Air Resources

Air is a common resource that we use every time we breathe

Large cities often have smog - mixture of chemicals that occurs as a grayish haze in the atmosphere

It is primarily due to car exhausts & industrial emissions

Air Resources

Pollutant - harmful material that can enter the biosphere through the land, air, or water

Burning of fossil fuels can release pollutants that cause smog & other problems

Air Resources

When chemical compounds combine with water vapor in the atmosphere, they form drops of nitric & sulfuric acid - Acid rain

Acid rain can kill plants by damaging their leaves & change the chemistry of soils & standing-water ecosystems

Freshwater Resources

Pollution threatens water supplies in the following ways:Wastes discarded on land can seep

through soil & enter underground waterChemicals can enter streams & riversSewage can encourage the growth of

algae & bacteria in aquatic habitats

The Value of Biodiversity

Biodiversity - the sum total of the genetically based variety of all organisms in the biosphere

Ecosystem diversity - the variety of habitats, communities, & ecological processes in the living world

The Value of Biodiversity

Species diversity - the # of different species in the biosphere

Genetic diversity - all the different forms of genetic information carried by all organisms living on Earth today

The Value of Biodiversity

Biodiversity is 1 of Earth’s greatest natural resources

Species of many kinds have provided us with foods, industrial products, & medicines - including painkillers, antibiotics, heart drugs, antidepressants, & anticancer drugs

Threats to Biodiversity

Human activity can reduce biodiversity by altering habitats, hunting species to extinction, introducing toxic compounds into food webs, & introducing foreign species to new environments

Threats to Biodiversity

Extinction - when a species disappears from all or part of its range

Endangered species - a species whose population size is declining in a way that places it in danger of extinction

Habitat Alteration

When land is developed, natural habitats may be destroyed

As habitats disappear, species that lived in those habitats also vanish

Development also splits ecosystems into pieces - habitat fragmentationEx.) Central Park

Demand for Wildlife Products

Humans have pushed some animal species to extinction by hunting them for food & other products

Today, endangered species are protected from hunting in the U.S.

Hunting still threatens rare animals in other countries, however

Pollution

Many forms of pollution can threaten biodiversity, especially when toxic compounds accumulate in the tissues of organisms

Biological magnification - when concentrations of a harmful substance increase in organisms at higher trophic levels in a food chain/ food web

Pollution

Introduced Species

1 of the most important threats to biodiversity today comes from apparently harmless plants & animals that humans transport around the world either accidentally or intentionally

Introduced Species

Introduced into new habitats, these organisms often become invasive species that reproduce rapidly

Invasive species - increase their populations because their new habitat lacks the parasites & predators that control their popul. “back home”

Conserving Biodiversity

Conservation - describes the wise management of natural resources, including the preservation of habitats & wildlife

Today, conservation efforts focus on protecting entire ecosystems as well as single species

Conserving Biodiversity

Protecting an ecosystem will ensure that the natural habitats & the interactions of many different species are preserved at the same time

By focusing on protecting specific ecosystems, biologists hope to preserve global biodiversity

Charting a Course for the Future

Researchers are gathering data to monitor & evaluate the effects of human activities on important systems in the biosphere

2 of these systems are the ozone layer high in the atmosphere & the global climate system

Ozone Depletion

Ozone layer - 20-50Km above Earth’s surface, a layer of high concentration of ozone gas exists

Ozone at ground level is a pollutant, but in the atmosphere, serves an important function

Ozone Depletion

It absorbs a harmful UV radiation from sunlight before it reaches Earth

Global Climate Change

Global warming - describes the increase in average temperature of the biosphere

1 sign is the melting polar ice cap