Chapter 26: Economic Development and

Global Ecology

Robert E. RicklefsThe Economy of Nature, Fifth Edition

1

Looking to the Future

As the human population continues to grow and humans dominate ecological systems worldwide, the question of how we can create a sustainable future for both humans and other species becomes increasingly important:

there is considerable room for pessimistic conclusionspositive steps have been taken in the United States:

Clean Air Act (1970)Clean Water Act (1972)Endangered Species Act (1973)But…

In Lebanon?

Positive Steps Toward Sustainability

Laws regarding endangered species, clean air, and clean water have been implemented worldwide.

Straightforward ecological and engineering solutions exist for environmental problems.

People worldwide share a concern for the environment.

What can Ecologists Contribute?

The challenge to ecologists is to provide the scientific information needed to develop social consensus, build political commitment, and inform decision making on issues concerning the environment.

Ecological processes hold the key to environmental policy.

Conserving ecological processes is the key to maintaining a sustainable biosphere:

the fundamental processes of energy use and recycling of materials have built-in mechanisms to restore imbalances when these occur:

when consumers increase to high numbers, declining birth rates and increasing death rates restore a sustainable relationship between consumer and resource

if natural processes are disrupted, ecosystems may not be able to maintain themselves

Human activities threaten local ecological processes.

All human activities have consequences for the environment:

emphasis on short-term returns can lead to collapse of a resource:

one after another of the commercial whale species were hunted to near-extinction, forcing the industry to turn progressively to less profitable species

many profitable fisheries have collapsed because of overfishing

Human activities threaten local ecological processes.

Some consequences of human activities have indirect effects:

clearing of watershed land for agriculture or timber leads to undesirable consequences downstream:

alteration of riverine habitats

siltation of dams

damage to reef habitats

Overexploitation

Fishing, hunting, grazing, and logging are classic consumer-resource interactions:

in natural systems, such interactions come into equilibrium:

efficiency of exploitation by consumers and resistance to exploitation by resources have evolved over long periods

humans have used technology to escalate beyond all natural limits their ability to overexploit natural resources, with undesirable consequences:

when resources are exhausted, human populations suffer

Sustainable and Unsustainable Practices

Consider the lowland tropics:soils contain few nutrients, with natural fertility maintained by recycling of nutrients between detritus and living plants:

clearcutting, especially when followed by grazing, breaks this cycle, resulting in a badly degraded systemhumans have learned to live sustainably in such ecosystems through the practice of shifting agriculture

by clearing 1-2% of the land per year and cultivating for 2 or 3 years, farmers allow sufficient time in fallow for nutrient stocks to recover from agriculture

Introduction of Exotic Species

Humans have taken other species with them everywhere they have traveled; for example:

50,000 nonindigenous species have been introduced to the United StatesNew Zealand has a predominantly alien flora and fauna:

most of the area is occupied by introduced plants and animals:

native forests were cut and replaced by eucalyptus

native moas were killed by Maori natives, replaced by European transplants

Why did aliens prosper in New Zealand?

Of the total New Zealand flora of 2,500 species, 500 are introduced:

introduced species account for most of the vegetation

why were these species so successful?most natural habitats had been disturbed

because of low diversity and simple structure, island ecosystems are generally more easily invaded

Can effects of aliens be predicted?

Alien species may displace natives, but do not necessarily disrupt ecosystems:

introduced species may simply assume the ecological roles of natives

effects of introduced species are hard to predict:

aliens may also be disruptive, altering ecosystem function and community structure:

Nile perch in Lake Victoria eliminated an entire trophic level of planktivorous fish

Habitat Conversion

Altering habitats can upset natural processes:cutting of tropical forests:

breaks the tight cycle of nutrient regeneration

results in increased erosion

plowing of prairies set the stage for the “dust bowl” conditions of the 1920s and 1930s in the United Statesdisruption of mangroves in tropical coastal areas have left the land vulnerable to hurricane-driven floodwatersdamming rivers increases silt transport, blocks fish migrations, alters downstream ecosystems

Irrigation

Benefits of irrigation are often offset by substantial environmental problems:

environmental costs associated with infrastructure (dams, canals, etc.)lowered water tables where wells are usedreduction of groundwater quality (through introduction of pesticides and fertilizers)

– accumulation of salt in irrigated lands– transmission of diseases by aquatic

organisms

Fertilization and Eutrophication 1

• Inorganic fertilizers (e.g., nitrates, phosphates) inevitably make their way into aquatic systems:– fertilization of aquatic systems

(eutrophication) leads to overproduction:• waters are no longer attractive for

recreational use• decaying organic matter can lead to

deoxygenation of water and fish kills

Fertilization and Eutrophication 2

• Addition of organic wastes poses a serious problem for water quality:– organic matter increases biological oxygen

demand, decreasing oxygen levels:• killing fish and other obligate aerobes• cutting migration routes for other species

• Problems associated with eutrophication can be avoided by:– cutting off or diverting sources of nutrients– improving treatment of organic wastes

Toxins

• Toxins are poisons:– these chemicals kill animals and plants by

interfering with normal physiological functions

– many toxins occur naturally, but humans have increased their accumulation in the environment

– various classes of toxins exist, including:• acids• heavy metals• organic compounds• radiation

Acids

• Two principal sources of acidity are associated with human activities:– acid mine drainage:

• oxidation of sulfur and thiol in mine wastes by bacteria creates sulfates, which become sulfuric acid in mine drainage– mine drainage may be sufficiently acidic as to

sterilize aquatic environments downstream

– acid rain, the result of combusting fossil fuels

Acid Rain• Burning of coal and oil releases nitrogen

oxides and sulfur dioxide into the atmosphere:– these gases dissolve in raindrops, creating acids:

• pH of rain may drop to as low as 3-4

– consequences of acid rain have been especially severe in industrialized areas:• direct impacts of acidity on aquatic systems• depletion of fertility in terrestrial systems

• Reducing emissions of sulfur and nitrogen oxides, reductions in energy use are solutions to acid rain.

Heavy Metals

• Mercury, arsenic, lead, copper, nickel, zinc, and other heavy metals are toxic even in low concentrations:– these enter the environment as byproducts of

mining, manufacturing, fungicides, fuels– emissions of heavy metals from smelting

operations have been especially troublesome:• emissions adversely affect mosses, lichens, fungi,

other soil organisms, vascular plants, and higher animals

• adverse effects may extend many km downwind of smelters

Organic Compounds 1

• Organic compounds have been introduced to many ecosystems in the form of pesticides:– classes include:

• organomercurials (methylmercury)• chlorinated hydrocarbons (DDT)• organophosphorus compounds (parathion)• carbamate insecticides• triazine herbicides

– these compounds may accumulate in ecosystems with adverse effects on unintended targets

Organic Compounds 2

• Can the adverse effects of pesticides be reduced?– modern pesticides and efficient delivery systems can

reduce unintended impacts– alternatives to chemical warfare against other

organisms can be explored– bioremediation (using biological agents to restore

habitats) can be explored

• Another anthropogenic impact caused by organic compounds is oil spills (3-6 x 106 tons annually):– oil kills by coating organisms, disrupting membranes

Radiation

• Of special concern are extremely energetic (short wavelength) forms of radiation and subatomic particles emitted by disintegration of atomic nuclei:– low levels occur naturally as background– extreme radiation hazards are posed by

nuclear power plants, nuclear wastes of various kinds, and nuclear war

– even peaceful uses of nuclear materials are limited by problems associated with disposal of long-lived wastes

Atmospheric Pollution

• Pollution of the oceans and atmosphere are of particular concern:– circulation leads to widespread distribution

of pollutants far beyond their sources– of greatest concern are two anthropogenic

effects on the atmosphere:• destruction of the ozone layer• increase in carbon dioxide, other greenhouse

gases

The Ozone Layer and Ultraviolet Radiation

• Ozone (O3) is molecular oxygen in a highly reactive form:– ozone readily oxidizes organic molecules– anthropogenic ozone near the earth’s

surface is a byproduct of combustion of fossil fuels:• nitrous oxide (NO2) combines with oxygen to

form ozone in the presence of sunlight • high levels of ozone are damaging to human

health, crops, and natural vegetation

Ozone in the Upper Atmosphere

• Naturally occurring ozone in the upper atmosphere absorbs ultraviolet radiation:– ozone thus shields earth’s surface from

damaging effects of UV radiation– reaction of chlorine with ozone in the upper

atmosphere breaks down ozone:• chlorine has increased as result of emissions of

CFCs (chlorofluorocarbons)• depletion of stratospheric ozone at high latitudes

has been referred to as ozone holes

Damaging Effects of Ozone Depletion

• Depletion of stratospheric ozone leads to increased UV radiation at the earth’s surface:– Consequences include

• damage to DNA and resultant cancers• reduced photosynthetic production by plants

• Ozone depletion is now addressed by conventions phasing out use of CFCs:– Vienna Convention for Protection of the Ozone

Layer (1985) – Montreal Protocol (1987)

Carbon Dioxide and the Greenhouse Effect 1

• Carbon dioxide (CO2) is a naturally occurring atmospheric component, at about 280 ppm in the preindustrial atmosphere.

• CO2 and several other atmospheric gases form an insulative layer, passing visible light, but absorbing longwave radiation emitted by the earth:– referred to as the greenhouse effect

Carbon Dioxide and the Greenhouse Effect 2

• CO2 levels have varied considerably during earth’s history:– at times in the past when CO2 levels were high,

earth was much warmer

• CO2 levels are now creeping upward as a result of combustion of fossil fuels and forest clearing:– CO2 level is now 350 ppm and increasing

– we are now faced with increasing global temperatures and related effects (such as rising sea levels)

Carbon Dioxide and the Greenhouse Effect 3

• Humans now add carbon to the atmosphere at a rate of about 7 billion tons annually:– the oceans absorb about 2.4 billion tons:

• this is insufficient to balance anthropogenic additions, so atmospheric levels will continue to rise

• Most effects of increased atmospheric CO2 and global warming will be negative:– increasing drought stress in arid environments– inundation of coastal areas by rising sea level

Human ecology is the ultimate challenge.

• If we are to leave a habitable world for future generations, our top priority must be to achieve a sustainable relationship with the rest of the biosphere. This will require:– putting an end to population growth– developing sustainable energy sources– providing for regeneration of nutrients

and other materials– restoring deteriorated habitats

Arable Land

Food Security

Population Growth

Food Production

Self Sufficiency Rate

Rise in Food PricesFood Deficit

Over Demand for Fish

Unsustainable Fishing Practices

Sea Food Supply

Fisherman Income

Over Demand

Increase in Oil and Energy Prices

Droughts

Biofuel and Food Competition

Increase in Speculative Trading

Market Policies

Water Shortage

Use of Cultivable Lands Desert Areas

Desertification

Overgrazing

Salination

Urban Expansion

Direct Compensating Variation (DCV)

Poverty

Rise in Extreme Poverty

Population Growth

Over DemandClimateChange

Migration to Urban Areas

Farmer’s Low Income

Future Scenarios

• Potential consequences of unrestrained population growth and human impacts are devastating:– energy and material shortages– many living in poverty and disease– a badly polluted environment– escalating social and political strife

• The future need not be like this…

Positive Alternatives

• Humankind has the choice of adopting a new attitude toward its relationship with nature. We are a part of nature, not apart from nature.

• To the extent that our intelligence, culture, and technology have given us the power to dominate nature, we must also use these abilities to impose self-regulation and self-restraint.

• We have succeeded famously in becoming the technological species. Our survival now depends on our becoming the ecological species and taking our appropriate place in the economy of nature.

Summary 1

• The key to human survival is the development of sustainable interactions with the biosphere.

• Local threats to integrity of natural systems are overexploitation of resources, introductions of exotic species, habitat conversion, irrigation, eutrophication, and production of toxic materials.

Summary 2

• Global threats to integrity of natural systems include depletion of stratospheric ozone and global warming caused by increasing atmospheric carbon dioxide.

• Solutions to the environmental crisis will require new attitudes promoting sustainability and self-restraint.