Environmental Encyclopedia

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Environmental Encyclopedia 3

Conservation biology

biodiversity to include the spatial and temporal changes of

communities on the greater landscape or seascape.

About 1.7 million of Earth’s species have been identi-

fied and given a scientific name. However, biologists have

not yet “discovered” most species, especially those living in

tropical habitats. According to some estimates, Earth may

support as many as 30–50 million species, of which 90%

occur in tropical ecosystems, particularly in old-growth rainf-

orests. Biologists believe that most of the unknown species

are invertebrates, especially species of beetles and other in-

sects. Compared with invertebrates, the numbers of species

of plants and vertebrate animals are relatively well known.

Biodiversity is valuable for many reasons, but these

can be grouped into the following three classes:

(1) Intrinsic value. Regardless of its worth in terms of

the needs of humans, biodiversity has its own,

intrinsic

value

(2) Utilitarian value. Humans have an undeniable need

to harvest wild and domesticated species and their communi-

ties as sources of food, materials, and energy. Although

harvests of biodiversity can be conducted in ways that foster

renewal, these potentially renewable resources are often har-

vested or managed too intensively, resulting in degradation

extinction

of the resource.

(3) Provision of ecological services. Biodiversity provides

numerous ecological services that are directly and indirectly

important to human welfare. These services include biologi-

cal productivity,

nutrient

cycling, cleansing of water and air,

control of

erosion

, provision of atmospheric oxygen and

removal of

carbon dioxide

, and other functions related to

the health and integrity of ecosystems. According to the

American biologist Peter Raven: “Biodiversity keeps the

planet habitable and ecosystems functional.”

Threats to biological diversity

Biodiversity at local, regional, continental, and global

scales is critically threatened by human activities. The dam-

ages that are being caused to Earth’s species and ecosystems

are so severe that they are referred to by ecologists as a

biodiversity crisis. Many permanent losses of biodiversity

have already been caused by human influences, including the

extinctions of numerous species and the losses of distinctive,

natural communities. Unless there are substantial changes

in the ways that humans affect ecosystems, there will be

enormously greater losses of biodiversity in the near future.

Earth’s natural biodiversity has always been subjected

to extinction (that is, the permanent loss of species and other

groups) The fossil record shows that species, families, and

even entire phyla have appeared and disappeared on Earth.

For example, many invertebrate phyla proliferated during

an evolutionary radiation at the beginning of the Cambrian

307

era about 570 million years ago, but most of these are now

extinct.

Many of the natural extinctions occurred simultane-

ously, apparently as a result of an unpredictable catastrophe.

For instance, about 65 million years ago a

mass extinction

occurred that resulted in the loss of the last of the dinosaurs

and as many as 76% of the then-existing species. That catas-

trophe is believed to have been caused by a meteorite im-

pacting Earth. In other cases, natural extinctions have been

caused by more gradual environmental changes, for example

in climate or in the intensity of disease or predation.

More recently, however, humans have been responsi-

ble for almost all of the extinctions that are occurring. In

fact, species are now being lost so quickly that the changes

represent a modern mass extinction. Well-known examples

of extinctions caused by humans include the

dodo

passen-

ger pigeon

, and great auk. Numerous other species have

been taken to the brink of extinction, including the plains

bison

whooping crane

ivory-billed woodpecker

, and

right whale. These losses have been caused by over-hunting

and the disturbance and conversion of natural habitats.

In addition to these famous cases involving large ani-

mals, an even more ruinous damage to Earth’s biodiversity

is being caused by extensive losses of tropical ecosystems,

particularly the conversion of tropical rain forests into ag-

ricultural habitats. Because tropical ecosystems are particu-

larly rich in numbers of species, loss of natural tropical

habi-

tat

causes extinctions of numerous species. Many of those

species occurred nowhere else but in particular tropical lo-

cales.

The mission of conservation biology is to understand

the causes and consequences of the modern crisis of extinc-

tion and degradation of Earth’s biodiversity, and then to

apply scientific principles to preventing or repairing the dam-

ages. This is largely done by conserving populations and by

protecting natural areas.

Conservation at the population level

In some cases,

endangered species

can be enhanced

by special programs that increase their breeding success and

enhance the survival of their populations. Usually, a variety

of actions is undertaken, along with the preservation of

appropriate habitat, under a scheme that is known as a

population recovery plan. Components of a population re-

covery plan may include such actions as (1) the careful moni-

toring of wild populations and the threats that they face;

(2) research into the specific habitat needs of the endangered

species; (3) the establishment of a captive-breeding program

and the release of surplus individuals into the wild; (4) re-

search into genetic variation within the species; and (5) other

studies of basic biology and ecology that are considered

necessary for preservation of the species, particularly in its

natural habitats. Unfortunately, population recovery plans

Environmental Encyclopedia 3

Conservation easements

have only been developed for a small fraction of endangered

species, and most of these have been prepared for species

that occur in relatively wealthy countries.

One example involves the whooping crane (Grus amer-

icana), an endangered species in North America. Because

of excessive hunting and

critical habitat

loss, this species

declined in abundance to the point where as few as only 15

individuals were alive in 1941. Since then, however, the wild

population of whooping cranes has been vigorously protected

in the United States and Canada, and their critical breeding,

migratory, and wintering habitats have been preserved. In

addition, the basic biology and behaviour of whooping cranes

have been studied, and some wild birds have been taken

into captivity and used in breeding programs to increase the

total population of the species. Some of the captive-bred

animals have been released to the wild, and whooping crane

eggs have also been introduced into the nests of the closely

related sandhill crane (Grus canadensis), which serve as foster

parents. These applications of conservation biology have

allowed the critically endangered population of whooping

cranes to increase to more than 150 individuals in the mid-

1980s, and to about 300 birds in 1997, of which about half

were in captivity. Because of these actions, there is now

guarded optimism for the survival of this endangered species.

Protected areas

Protected areas such as parks and ecological reserves

are necessary for the conservation of biodiversity in wild,

natural ecosystems. Most protected areas are established for

the preservation of natural values, particularly the known

habitats of endangered species, threatened ecological com-

munities, or representative examples of widespread commu-

nities. However, many protected areas (particularly parks)

are also used for human activities, as long as they do not

severely threaten the ecological values that are being con-

served. These uses can include

ecotourism

, and in some

cases fishing, hunting, and even timber harvesting. In 1993

there were about 9,000 protected areas globally, with a total

area of almost two million acres (792 million ha). Of this

total, about 2,500 sites comprising 1.15 million acres (464

million ha) were fully protected, and could be considered to

be ecological reserves.

Ideally, a national system of protected areas would

provide for the longer-term conservation of all native species

and their natural communities, including terrestrial, freshwa-

ter, and marine ecosystems. So far, however, no country has

implemented a comprehensive system of ecological reserves

to fully protect the natural biodiversity of the region. More-

over, many existing reserves are relatively small and are

threatened by environmental changes and other distur-

bances, such as illegal hunting of animals and plants and

sometimes intensive tourism.

308

Ecological knowledge has allowed conservation biolo-

gists to make important contributions to the optimized de-

sign of networks of protected areas. Important considerations

include: (1) the need to protect areas that provide adequate

representation of all types of natural ecosystems; (2) the need

to preserve all endangered ecosystems and the habitats of

threatened species; (3) the requirement of redundancy, so

that if one example of an endangered

ecosystem

becomes

lost through an unavoidable natural disturbance (such as a

hurricane

wildfire

), the type will continue to survive in

another protected area; (4) the need to decide whether or

not the network of protected areas should be linked by

corridors, a matter of some controversy among ecologists.

Conservation biology has also made important contri-

butions towards the spatial design of individual protected

areas. Important considerations include (1) the need to make

protected areas as large as possible, which will help to allow

species and ecosystems to better cope with disturbances and

environmental changes; (2) a preference for smaller reserves

to have a minimal amount of edge, which helps to avoid

damages that can be caused by certain predators and invasive

species; (3) the need to take an ecosystem approach which

ensues that the reserve and its surrounding area will be

managed in an integrated manner.

Although conservation biology is a relatively young

field, important progress is being made towards development

of the effective ecological and biological tools necessary to

preserve biodiversity.

[Bill Freedman Ph.D.]

ESOURCES

OOKS

Freedman, B. Environmental Ecology, 2nd edition. Academic Press, San

Diego, 1995.

Primack, R.B. Essentials of Conservation Biology. Sunderland, MA: Sinauer

Associates, 1993.

Wilson, E.O. (ed.). Biodiversity. Washington, D.C: National Academy

Press, 1988.

Conservation design

see

Urban sprawl

Conservation easements

conservation

easement is a covenant, restriction, or

condition in a deed, will, or other legal document that allows

the owner to maintain ownership and control of real prop-

erty, but restricts the use of that property so the land is

conserved in its natural state, or, in the case of a historic

conservation easement, so that it provides a historic benefit.

Environmental Encyclopedia 3

Conservation Reserve Program

The uses allowed by the easement can include

recreation

agriculture, cultural uses, and establishment of

wildlife hab-

itat

. The federal government allows tax deductions for con-

servation easements that provide a certified value to the

public, such as protecting ecologically valuable natural habi-

tat or, in the case of an easement based on the historical

conservation of the property, that contribute to the historic

character of the district in which the property is located.

Conservation easements are legal instruments enabled by

many states as well as non-United States governments, in-

cluding Canada and most of its provinces.

[Marie H. Bundy]

Conservation International

Conservation International (CI) is a non-profit, private orga-

nization dedicated to saving the world’s endangered rain

forests and the plants and animals that rely on these habitats

for survival. CI is basically a scientific organization, a fact

which distinguishes it from other conservation groups. Its

staff includes leading scientists in the fields of botany, orni-

thology, herpetology, marine biology, entomology, and zo-

ology.

Founded in 1987 when it split off from

the Nature

Conservancy

, CI now has over 55,000 members. The

group, headed by Peter A. Seligmann, has gathered accolades

since its inception. In 1991 Outside Magazine gave CI an

A- (one of the two highest grades received) in its yearly

report card rating 14 leading environmental groups.

The high praise is well founded. CI tends to success-

fully implement its many projects and goals. Many CI pro-

grams focus on building local capacity for conservation in

developing countries through financial and technical support

of local communities, private organizations, and government

agencies. Their “ecosystem conservation” approach balances

conservation goals with local economic needs. CI also funds

and provides technical support to local communities, private

organizations, and government agencies to help build sus-

tainable economies while protecting

rain forest

ecosystems.

Four broad themes underlie all CI projects: 1) a focus

on entire ecosystems; 2) integration of economic interests

with ecological interests; 3) creation of a base of scientific

knowledge necessary to make conservation-minded deci-

sions; and 4) an effort to make it possible for conservation

to be understood and implemented at the local level.

CI is involved with projects in 30 countries, including

Botswana, Brazil, Canada, Colombia, Indonesia, Mexico,

New Guinea, and the Philippines. In 2000, CI expanded

into Cambodia and China, among others.

Among CI’s many successful projects is the Rapid

Assessment Program (RAP), which enlists the world’s top

309

field scientists to identify

wilderness

areas in need of urgent

conservation attention. RAP teams have completed surveys

in Bolivia, Ecuador, Belize, Peru, and Mexico, and CI plans

at least 12 more surveys on four continents in the next

three to five years. CI has also helped establish important

biosphere

reserves in rain forest countries. These efforts

successfully demonstrate CI’s

ecosystem

conservation ap-

proach, and prove that the economic needs of local commu-

nities can be reconciled with conservation needs. No harvest-

ing or

hunting

is allowed in the reserves, but

buffer

zones,

which include villages and towns, are located just outside

the core areas.

CI strongly supports many educational programs. In

1988, it signed a long-term assistance agreement with Stan-

ford University which involves exchange and training of

Costa Rican students and resource managers. In 1989 CI

began a program with the University of San Carlos which

provides financial and technical support to the research activ-

ities in northern Guatemala of the university’s Center for

Conservation Studies. An educational program of a different

kind, the Sorcerer’s Apprentice, is designed to record ethno-

botanical knowledge, protect useful

species

, and pass this

information on to the next generation in indigenous commu-

nities. Young men and women in forestry services learn from

traditional village healers and midwives.

In 2002, CI has already established several new ways

to educate the people and help the

environment

, such as

Centers for

Biodiversity

Conservation, the Global Conser-

vation Fund, and a joint venture with Ford Motor Company

called the Center for Environmental Leadership in Business.

CI also focuses on activities in the major wilderness areas

identified as the most endangered. The organization also

has expanded its conservation efforts to new ecosystems,

including marine,

desert

, and temperate rain forest regions.

[Cathy M. Falk]

RGANIZATIONS

Conservation International, 1919 M Street, NW Suite 600, Washington,

D.C. USA 20036 (202) 912-1000, Toll Free: (800) 406-2306, Email:

inquiry@conservation.org, <http://www.conservation.org>

Conservation Reserve Program

The Conservation Reserve Program (CRP) is a voluntary

program for agricultural landowners, that encourages farmers

to plant long-term resource-conserving vegetative ground

cover to improve

soil

and water, and create more suitable

habitat

for fish and

wildlife

. Ground cover options include

grasses, legumes, shrubs, and tree plantings. The program

is authorized by the federal Food Security Act of 1985,

as amended, and is implemented through the Commodity

Environmental Encyclopedia 3

Conservation Reserve Program

Credit Corporation (CCC). It aims to promote good

land

stewardship

and improve rural aesthetics.

The CRP offers annual rental payments, incentive

payments, and cost-share assistance to establish approved

cover on eligible cropland. The CCC provides assistance of

as much as 50% of the landowner’s cost in establishing an

approved conservation program. Contracts remain in effect

for between 10 and 15 years. Annual rental payments are

based on the agriculture rental value of the land used in the

program. The program provides needed income support for

farmers, and helps to curb production of surplus commod-

ities.

Eligibility for participation in CRP extends to individ-

uals, partnerships, associations, Indian tribal ventures corpo-

rations, estates, trusts, other business enterprises or legal

entities. States, political subdivisions of states, or agencies

thereof owning or operating croplands, may also apply.

The CCC via the Farm Service Agency (FSA) man-

ages the CRP. The Natural Resources Conservation Service

(NRCS) and the Cooperative State Research and Education

Extension Service provide support. State forestry agencies

and local soil and

water conservation

districts also provide

assistance.

To be eligible for the CRP, cropland should have been

planted or considered planted to an agricultural commodity

in two of the five most recent crop years. Eligibility encom-

passes highly

erodible

acreage, cropped

wetlands

, and land

surrounding non-cropped wetlands. The cropland must be

owned or operated for at least 12 months before the close

of the sign-up period. Exceptions can be made for land that

was acquired by will or

succession

, or if the FSA determines

that ownership was not acquired for the purpose of placing

the land in the conservation reserve.

Initially,

erosion

reduction was the sole criterion for

acceptance in the CRP, and in 1986–87, 22 million acres

(8.9 million ha) were enrolled for this purpose. CRP proved

to be effective. According NRCS

statistics

, average erosion

on enrolled acres declined by about 90%. It was estimated

that the program reduced overall erosion nationwide by more

than 22% even though less than 10% of the nation’s cropland

was enrolled.

An Environmental Benefits Index (EBI) is used to

prioritize applications for the CRP. EBI factors include:

Wildlife habitat benefits,

water quality

benefits from re-

duced erosion,

runoff

, and

leaching

, and

air quality

bene-

fits from reduced wind erosion. The NRCS collects data for

each of the factors and, based on its analysis, applications

are ranked. Selections are made from that ranking.

The CCC bases rental rates on the productivity of

soils within a county, and the average rent for the past three

years of local agricultural land. The maximum CRP rental

rate for each applicant is calculated in advance of enrollment.

310

Applicants may accept that rate, or may offer a lower rental

rate to increase the likelihood that their project will be

funded.

The CCC encourages restoration of wetlands by pro-

viding a 25% incentive payment of the costs involved to

establish approved cover. This is in addition to the normal

50% cost share for non-wetlands. Eligible acreage devoted

to special conservation practices, such as riparian buffers,

filter strips, grassed waterways, shelter belts, living snow

fences, contour grass strips, salt tolerant vegetation, and

shallow water areas for wildlife, may be enrolled at any time

and is not subject to competitive bidding.

When CRP contracts expire, participants must con-

tinue to follow approved conservation plans. They must

comply with wetland,

endangered species

and other fed-

eral, state, and local environmental laws, and they must

respect any continuing conservation easement on the

property.

The United States Department of Agriculture

(USDA) provides information and technical assistance to

CRP participants who wish to return CRP land to row-

crop producing status as their contracts expire. This is to

ensure that the land is developed in a sound, productive, and

sustainable manner, preventing excessive erosion, protecting

water quality, and employing other measures that enhance

soil moisture-retaining ability.

In states such as North Dakota, the landscape has

been changed dramatically since the introduction of the

CRP. In the 1970s and early 1980s, fields with steep hills

and areas of light soil were often cultivated from fencerow-

to-fencerow. The result often was severe erosion and perma-

nent loss of soil fertility. In some areas, winters were domi-

nated by “snirtstorms” when a combination of dirt and snow

blew across the landscape depositing a dark coating on coun-

tryside downwind. In contrast, today’s travelers find these

landscapes covered with green vegetation in summer and

white snow in winter.

The CRP has particularly benefited migratory birds

in states such as North Dakota, South Dakota, and Montana.

The perennial vegetation on marginal farmland has provided

refuge for migrating birds, and added breeding habitat for

others. North Dakota farmers have enrolled about 10% of

the state’s cropland in the CRP.

The fiscal year 2000 federal agricultural appropriations

bill authorized a pilot project of harvesting of

biomass

from

CRP land to be used for energy production. Six projects

were authorized, no more than one of which could be in

any state. Vegetation could not be harvested more often than

once every two years, and no commercial use could be made

of the harvested biomass other than energy production. An-

nual CRP rental payments are reduced by twenty five percent

during the year the acreage is harvested. Land that is devoted

Environmental Encyclopedia 3

Conservation Reserve Program

to field windbreaks, waterways, shallow water ways for wild-

life, contour grass strips, shelter belts, living snow fences,

permanent vegetation to reduce

salinity

, salt tolerant vegeta-

tive cover, filter strips, riparian buffers, wetland restoration,

and cross-wind trap strips is not eligible for this program.

By 2002, contracts had been approved in Iowa, Illinois,

Oklahoma, Minnesota, New York, and Pennsylvania.

In June of 2001, the USDA announced a six-state

pilot program as part of the CRP to restore up to 500,000

acres (202,000 ha) of farmable wetlands and associated buff-

ers. The Farmable Wetlands Pilot Program is intended to

help producers improve the

hydrology

and vegetation of

eligible land in Iowa, Minnesota, Montana, Nebraska, North

Dakota, and South Dakota. Restoring wetlands in these

states should reduce downstream flood damage, improve

surface and

groundwater

quality, and recharge ground-

water supplies. Essential habitat for migratory birds and

many other wildlife

species

, including threatened and en-

dangered species will be created and enhanced. Recreational

activities such as hiking and bird watching will also be im-

proved.

In 1985, the year in which CRP originated, spring

surveys by the U.S

Fish and Wildlife Service

estimated

waterfowl breeding populations at 25.6 million ducks. A fall

flight of 54.5 million was predicted. Several species of ducks

including mallards, pintails, and blue-winged teal appeared

to be fading away. Numbers were at or near their lowest

ebb in 30 years. Between 1986 and 1990, farmers enrolled

8.2 million acres (3.3 million hectare) of cropland in CRP

within an area known as the

prairie

pothole region. This

large glaciated area of the north central United States and

southern Canada is where up to 70% of North America’s

ducks are hatched. Through CRP, nearly 13,000 mi

(34,000

) was converted to superior nesting habitat through

CRP.

In the early 1990s, increased precipitation filled the

prairie potholes and many waterfowl ended their spring

mi-

gration

on CRP land, rather than continuing migration to

their usual breeding grounds in Canada. Nesting densities

increased many fold. Potholes surrounded by CRP grass

provided more secure habitat for nests, and hatchlings were

no longer easy targets for predators. Nesting success tripled,

from 10 to 30%, and waterfowl

mortality

no longer exceeded

annual additions. By 1995, ten years after the start of CRP,

36.9 million ducks were included in the annual spring survey

numbers, a 40% increase in 10 years.

Waterfowl are not the only bird species to benefit from

CRP. In one study, breeding birds were counted in about

400 fields in eastern Montana, North and South Dakota,

and western Minnesota. These states have nearly 30% of all

land included in the CRP. Fields were planted mostly to

mixtures of native and introduced grasses and legumes. For

311

most of the seventy-three different species counted, numbers

were far higher in CRP fields than in cropland. Differences

were greatest for several grassland species whose numbers

had been markedly declining in recent surveys. Two species,

lark buntings (Calamospiza melanocorys ) and grasshopper

sparrows (Ammodramus savannarum ), were 10 and 16 times

more common in CRP

environment

than in cropland. The

investigators concluded that restoration of suitable habitat

in the form of introduced grasses and legumes can have an

enormous beneficial effect on populations of grassland birds.

When CRP was due to expire in 1995, restoration of

prairie pothole breeding grounds was in jeopardy. United

States farm policy was undergoing major change and it ap-

peared that the CRP would not be continued.

Ducks Unlim-

ited

and other wildlife organizations lobbied heavily, and

funding of one billion dollars was included in the 1996

Farm Bill to continue the program for another seven years.

Moreover, the guidelines for the continuing program were

geared more directly to the preservation of wetlands and

waterfowl conservation. The prairie pothole region was des-

ignated a national conservation priority area, and during the

March 1997 sign-up more acres in the prairie pothole region

were enrolled in CRP than were due to expire.

In its first 10 years, the CRP cost nearly $2 billion

per year. Opponents have argued that this is too expensive,

while proponents maintain that the costs are offset by its

conservation and environmental benefits. Estimates of the

annual value of benefits range from slightly less than $1

billion to more than $1.5 billion. Some analysts claim that

the value of benefits approaches or exceeds costs in some

sites.

The USDA announced that there would not be general

CRP signup for Fiscal Year 2002 although producers could

continue to enroll acreage eligible under continuous enroll-

ment provisions. Later, they announced that CRP contracts

expiring in 2002 could be extended for another year.

[Douglas C. Pratt Ph.D.]

ESOURCES

ERIODICALS

2002 Ducks Unlimited, Inc. May 31, 2002 [June 2002]. <http://www.duck-

s.org/conservation/crp.asp>.

Conservation Reserve Program Biomass Pilot Projects. U.S. Department of

Agriculture, Farm Service Agency Online. Fact Sheet Electronic Edition.

November 2000 [May 2002].

Kantrud, Harold A., Rolf R. Koford, Douglas H. Johnson, and Michael

D. Schwartz.” The Conservation Reserve Program—Good for Birds of

Many Feathers.” North Dakota Outdoors 56, no. 2: 14–17.

Johnson, D. H., and M. D. Schwartz. “The Conservation Reserve Program

and Grassland birds.” Conservation Biology 7: 934–937.

New Conservation Reserve Program The University of Georgia, Cooperative

Extension Service Extension, Forest Resources Unit. FOR. 97-003. 1997

[May 2002].

Environmental Encyclopedia 3

Conservation tillage

USDA To Help Restore Wetlands Through Six-state Pilot Programs. Farm

Service Agency Public Affairs Staff June 4, 2001 [June 2002].

Conservation tillage

Conservation

tillage is any

tilth

sequence that reduces loss

soil

or water in farmland. It is often a form of non-

inversion tillage that retains significant amounts of plant

residues on the surface. Thirty percent of the soil surface

must be covered with plant residues at crop planting time

to qualify as conservation tillage under the Conservation

Technology Information Center definition. Other forms of

conservation tillage include ridge tillage, rough plowing, and

tillage that incorporates plant residues in the top few inches

of soil.

A number of implements for primary tillage are used

to retain all or a part of the residues from the previous crop

on the soil surface. These include machines that fracture the

soil, such as chisel plows, combination chisel plows, disk

harrows, field cultivators, undercutters, and strip tillage ma-

chines. In a no-till system, the soil is not disturbed before

planting. Most tillage systems that employ the moldboard

plow are not considered conservation tillage because the

moldboard plow leaves only a small amount of residue on

the soil surface (0–10%).

When compared with conventional tillage (moldboard

plow with no residue on the surface), various benefits from

conservation tillage have been reported. Chief among the

benefits are reduced wind and water

erosion

and improved

water conservation

. Erosion reductions from 50–90% as

compared with conventional tillage are common. Conserva-

tion tillage often relies on herbicides to help control weeds

and may require little or no post-planting cultivation for

control of weeds in row crops. Depending on the manage-

ment system used,

herbicide

amounts may or may not be

greater than the amounts used on conventionally tilled land.

Yields from conservation tillage, particularly corn, may be

greater or smaller than from conventional tilled soil. Crop

yield problems are most frequent on wet soils in the northern

United States. Costs of tillage may be lower, but not always,

from conservation tillage as compared with conventional.

[William E. Larson]

ESOURCES

OOKS

Little, C. E. Green Fields Forever: The Conservation Tillage Revolution in

America. Covelo, CA: Island Press, 1987.

312

Consultative Group on International

Agricultural Research

The Consultative Group on International Agricultural Re-

search (CGIAR) was founded in 1971 to improve food

production in developing countries. Research into agricul-

tural productivity and the management of

natural re-

sources

are the two goals of this organization, and it is

dedicated to making the scientific advances of industrialized

nations available to poorer countries. The CGIAR empha-

sizes the importance of developing sustainable increases in

agricultural yields and creating technologies that can be used

by farmers with limited financial resources.

Membership consists of governments, private founda-

tions, and international and regional organizations. The

goals of this association are carried out by a network of

International Agricultural Research Centers (IARCs). There

are currently 18 such centers throughout the world, all but

four of them in developing countries, and they are each

legally distinct entities, over which the CGIAR has no direct

authority. The group has no constitution or by-laws, and

decisions are reached by consensus after consultations with

its members, either informally or at their semiannual meet-

ings. The function of the CGIAR is to assist and advise the

IARCs, and to this end it maintains a Technical Advisory

Committee (TAC) of scientists who review ongoing research

programs at each center.

Each IARC has its own board of trustees as well as

its own management, and they formulate individual research

programs. The research centers pursue different goals, ad-

dressing problems in a particular sector of agriculture, such

as livestock production or agricultural challenges in specific

parts of the world, such as crop production in the semi-arid

regions of Africa and Asia. Some centers conduct research

into integrated plant protection, and others into forestry,

while some are more concerned with policy issues, such as

food distribution and the international food trade. One of

the priorities of the CGIAR is the

conservation

of seed and

plant material, known as germplasm, and the development of

policies and programs to ensure that these resources are

available and fully utilized in developing countries. The In-

ternational Board for Plant Genetic Resources is devoted

exclusively to this goal. Besides research, the basic function

of the IARCs is educational, and in the past two decades

over 45,000 scientists have been trained in the CGIAR

system.

The central challenge facing the CGIAR is world

population growth

and the need to increase agricultural

production by nearly 50% in the next 20 years while preserv-

ing natural resources. The group was one of the main con-

tributors to the so-called “Green Revolution.” It helped de-

velop new high-yielding varieties of cereals and introduced

Environmental Encyclopedia 3

Container deposit legislation

them into countries previously unable to grow the food;

some of these countries now have agricultural surpluses. In

2001, CGIAR in South Africa worked on developing two

new types of maize, which have a 30–50% larger crop than

what is currently being produced by the smaller farmers.

The CGIAR is working to increase production even further,

narrowing the gap between actual and potential yields, while

continuing its efforts to limit

soil erosion

desertification

and other kinds of

environmental degradation

The

World Bank

, the Food and Agriculture Organi-

zation (FAO) and the United Nations Development Pro-

gram (UNDP) are among the original sponsors of the

CGIAR, and the organization has its headquarters at the

offices of the World Bank, which also funds central staffing

positions. Combined funding has grown from $15 million

in 1971 to over $340 million in 1999, and the CGIAR has

a staff of 12,000 worldwide. The group publishes a newsletter

called CGIAR Highlights.

[Douglas Smith]

ESOURCES

RGANIZATIONS

CGIAR Secretariat, The World Bank, MSN G6-601, 1818 H Street NW,

Washington, D.C. USA 20433 (202) 473-8951, Fax: (202) 473-8110,

Email: cgiar@cgiar.org, <http://www.cgiar.org>

Container deposit legislation

Container deposit legislation requires payment of a deposit

on the sale of most or all beverage containers and may require

that a certain%age of beverage containers be allocated for

refillables. The legislation shifts the costs of collecting and

processing beverage containers from local governments and

taxpayers to manufacturers, retailers and consumers.

While laws vary from state to state, even city to city,

container deposit legislation generally provides a monetary

incentive for returning beverage cans and bottles for

recycl-

ing

. Distributors and bottlers are required to collect a deposit

from the retailer on each can and bottle sold. The retailer

collects the deposit from consumers, reimbursing the con-

sumer when the container is returned to the store. The

retailer then collects the deposit from the distributor or

bottler, completing the cycle. Consumers who choose not

to return their cans and bottles lose their deposit, which

usually becomes the property of the distributors and bottlers,

though in some states, unredeemed deposits are collected

by the state.

Oregon implemented the first deposit law or “bottle

bill” in 1972. In the 1970s and 1980s, industry opponents

fought container deposit laws on the grounds that they would

result in a loss of jobs, an increase in prices, and a reduction

313

in sales. Now opponents denounce the legislation as being

detrimental to curbside recycling programs. But over the

past two decades, container deposit legislation has proven

effective not only in controlling litter and conserving

natural

resources

but in reducing the

waste stream

as well.

Recovery rates for beverage containers covered under

the deposit system depend on the amount of deposit and the

size of the container. The overall recovery rate for beverage

containers ranges from 75 to 93%. The reduction in con-

tainer litter after implementation of the deposit law ranges

from 42 to 86%, and reduction in total volume ranges from

30 to 60%. Although beverage containers make up just over

5% by weight of all

municipal solid waste

generated in

the United States, they account for nearly 10% of all waste

recovered, according to the

Environmental Protection

Agency

(EPA). While the cans and bottles that are recycled

into new containers or new products ease the burden on the

environment

, recycling is a second-best solution.

As recently as 1960, 95% of all soft drinks and 53%

of all packaged beer was sold in refillable glass bottles. Those

bottles required a deposit and were returned for

reuse

or more times. But the centralization of the beverage indus-

try, the increased mobility of consumers, and the desire

for convenience resulted in the virtual disappearance of the

reusable beverage container. Today, refillables make up less

than 6% by volume of packaged soft drinks and 5% by

volume of packaged beer, and these percentages shrink every

year, according to the National Soft Drink Association and

the Beer Institute.

Reuse is a more environmentally responsible

waste

management

option, and is superior to recycling in the

waste reduction

hierarchy established by the EPA. While

the container industry has been unwilling to promote refill-

able bottles, new interest in container deposit legislation may

move industries and governments to adopt reuse as part of

their waste management practices.

Industry-funded studies have found that a refillable

glass bottle used as few as eight times consumes less energy

than any other container, including recycled containers. A

study conducted for the National Association for Plastic

Container Recovery found that the 16-oz (1 pt) refillable

bottle produces the least amount of waterborne waste and

fewest atmospheric emissions of all container types.

To date, 10 states and one city have enacted beverage

container deposit systems, designed to collect and process

beverage bottles and cans. A deposit of 5–10 cents per can

or bottle is an economic incentive to return the container.

The states that have some form of container deposit legisla-

tion and accompanying deposit system include Oregon, New

York, Connecticut, Maine, Iowa, Vermont, Michigan, Mas-

sachusetts, Delaware, and California. Legislation is pending

in 25 state legislatures, and on

Earth Day

1993, a national

Environmental Encyclopedia 3

Contaminated soil

bottle bill was introduced in the U.S. Congress by sponsors

from the House of Representatives.

Despite the fact that opinion polls show the public

supports bottle bills by a nearly three-to-one margin, for

two decades the beverage and packaging industries have

successfully blocked the passage of bottle bills in nearly 40

states and even the most successful container deposit pro-

grams have come under attack and are threatened with

repeal.

Connecticut has one of the highest percentages of

refillable beer bottles in the nation, according to

statistics

from the Beer Institute. Despite the success of the state’s

five-cents-per-container deposit legislation, Governor Low-

ell Weicker Jr. has pushed for repeal of the legislation, to

be replaced by a five-cents-per-container tax to benefit the

state parks system. Opponents to Weicker’s plan insist that

the repeal of the deposit law would result in greater numbers

of bottles and cans left strewn across the state.

Others predict the repeal of the bottle bill would im-

pact the state in other ways: about 1,000 jobs would be lost;

small redemption centers would go out of business; and

recycling rates for glass,

aluminum

and plastic would drop.

In addition, it has been estimated that repeal would cost

municipal curbside recycling programs in Connecticut be-

tween $5.4 and $12.5 million annually.

The United States has a long way to go to catch up

to progressive countries such as Sweden, which does not

allow aluminum cans to be manufactured or sold without

industry assurances of a 75% recycling rate. Concerned that

voluntary recycling would not meet these standards, the

beverage, packaging and retail industries in Sweden have

devised a deposit-refund system to collect used aluminum

cans. Consumers in Sweden return their aluminum cans at

a rate that has not been achieved in any other country. The

75% recycling rate was achieved in 1987, and industry experts

expect the rate to exceed 86% in 1993. Most North American

deposit systems rely on the distributor or bottler, but the

deposit in Sweden originates with the can manufacturer or

drink importer delivering cans within the country. Also,

retail participation is voluntary: retailers collect the deposit

but are not required to redeem the containers, though

most do.

In 1991, 122 billion containers, weighing about 7.2

million tons, were produced in the United States—a 100%

increase in packaging waste since 1960. Containers and

packaging are the single largest component of the waste

stream and they offer the greatest potential for reduction,

reuse, and recycling, according to the EPA. Where individu-

als, industries, and governments will not voluntarily comply

with recycling programs, container deposit legislation has

314

decreased the amount of

recyclables

entering the waste

stream.

[Linda Rehkopf]

ESOURCES

ERIODICALS

Franklin, P. “Sweden’s Aluminum Can Return System.” Resource Recycling

(March 1993): 66.

Langer, G. “Many Happy Returns.” Sierra 73 (March-April 1988): 19-22.

Williams, T. “The Metamorphosis of Keep America Beautiful.” Audubon

92 (March 1990): 124-133.

Containment structures

see

Nuclear power

Contaminated soil

The presence of pollutants in soils at concentrations above

background levels that pose a potential health or ecological

risk. Soils can be contaminated by many human actions

including the

discharge

of solids and liquid pollutants at

the

soil

surface;

pesticide

application; subsurface releases

from leaks in buried tanks, pipes, and landfills; and deposi-

tion of atmospheric contaminants such as dusts and particles

containing

lead

. Common contaminants include volatile

hydrocarbons—such as

benzene

toluene

, ethylene, and

xylene

(BTEX compounds)—found in fuels; heavy paraf-

fins and chlorinated organic compounds such as polychlori-

nated biphenyl (PCB) and

pentachlorophenol

(PCP); in-

organic compounds such as lead,

cadmium

arsenic

and

mercury

; and

radionuclides

such as tritium. Often, soil is

contaminated with a mixture of contaminants. The nature of

soil, the contaminant’s chemical and physical characteristics,

and environmental factors such as

climate

and

hydrology

interact to determine the accumulation, mobility, toxicity,

and overall significance of the contaminant in any specific

instance.

Fate of soil contaminants

Contaminants in soils may be present in solid, liquid,

and gaseous phases. When liquids are released, they move

downward through the soil. Some may fill pore spaces as

liquids, some may partition or sorb onto mineral soil surfaces,

some may dissolve into water in the soft pores, and some may

volatilize. For most

hydrocarbons

, a multiphase system is

common. When contaminants reach the

water table

(where

the voids between soil particles are completely filled with

water), contaminant behavior depends on its density. Light

BTEX-type compounds float on the water table while dense

chlorinated compounds may sink. While many hydrocarbon

compounds are not very soluble, even low levels of dissolved

Environmental Encyclopedia 3

Contaminated soil

contaminants may produce unsafe or unacceptable

ground-

water

quality. Other contaminants such as inorganic salts,

such as

nitrates

, may be highly soluble and move rapidly

through the

environment

. Metals demonstrate a range of

behaviors. Some may be chemically bound and thus quite

immobile; some may dissolve and be transported by ground-

water and

infiltration

Contaminated pore water, called leachate, may be

transported in the groundwater flow. Groundwater travels

both horizontally and vertically. A portion of the contami-

nant, called residual, is often left behind as the flow passes,

thus contaminating soils after the major contaminant

plume

has passed. If the groundwater velocity is fast, for example,

hundreds of feet per year, the zone of contamination may

spread quickly, potentially contaminating extraction

wells

or other resources. Over years or decades, especially in sandy

or porous soils, groundwater contaminants and leachate may

be transported over distances of miles, producing a situation

that is very difficult and expensive to remedy. In these cases,

immediate action is needed to contain and clean up the

contamination. In cases where soils are largely comprised of

fine-grained silts and clays, contaminants may spread very

slowly. Such examples show the importance of site-specific

factors in evaluating the significance of soil contamination

as well as the selection of a cleanup strategy.

Superfund and other legislation

Prior to the 1970s, inappropriate land disposal prac-

tices, such as dumping untreated liquids in lagoons and

landfills, were common and widespread. The presence and

potential impacts of soil contamination were brought to

public attention after well-publicized incidents at

Love Ca-

nal

, New York and the Valley of the Drums. Congress

responded by passing the

Comprehensive Environmental

Response, Compensation, and Liability Act

in 1980 (com-

monly known as CERCLA or Superfund) to provide funds

with which to cleanup the worst sites. After five years of

much litigation but little action, Congress updated this law in

1986 with the Superfund Amendments and Reauthorization

Act. At present, about 1,200 sites across the United States

have been selected as

National Priorities List

(NPL) sites

and are eligible under CERCLA for federal assistance for

cleanup. These Superfund sites tend to be the nation’s largest

and worst sites in terms of the possibility for adverse human

and environmental impacts and the most expensive ones to

clean up. While not as well recognized, numerous other sites

have serious soil contamination problems. The U.S. Office

of Technology Assessment and

Environmental Protection

Agency

(EPA) estimate that about 20,000 abandoned waste

sites and 600,000 other sites of land contamination exist in

the United States. These estimates exclude soils contami-

nated with lead in older city areas, the accumulation of

fertilizers, pesticides, and insecticides in agricultural lands,

315

and other classes of potentially significant soil contamina-

tion. Federal and state programs address only some of these

sites. Currently, CERCLA is the EPA’s largest program,

with expenditures exceeding three billion dollars over the

last 15 years. However, this is only a fraction of the cost to

government and industry that will be needed to cleanup all

waste sites. Typical estimates of funds required to mitigate

the worst 9,000 waste sites reach at least $500 billion; a 50-

year time period is anticipated. The problem of contaminated

soil is significant not only in the United States but in all

industrialized countries.

U.S. laws such as CERCLA and the

Resource Con-

servation and Recovery Act

(RCRA) attempt to prohibit

practices that have led to extensive soil contamination in the

past. These laws restrict disposal practices; mandate financial

liability to recover cleanup costs (as well as personal injury

and property damage) and criminal liability to discourage

willful misconduct or negligence; require record keeping to

track waste; and provide incentives to reduce waste genera-

tion and improve

waste management

Soil cleanups

The cleanup or

remediation

of contaminated soils

takes two major approaches: source control and containment,

or soil and residual treatment and management. Typical

containment approaches include caps and covers over the

waste in order to limit infiltration of rain and snow melt

and thus decrease the leachate from the contaminated soils.

Horizontal transport in near-surface soils and groundwater

may be controlled by vertical

slurry

walls. Clay, cement,

or synthetic membranes may be used to encapsulate soil

contaminants. Contaminated water and leachate may be

hydraulically isolated and managed with groundwater pump-

and-treat systems, sometimes coupled with the injection of

clean water to control the spread of contaminants. Such

containment approaches only reduce the mobility of the

contaminant, and the barriers used to isolate the waste must

be maintained indefinitely.

The second approach treats the soil to reduce the

toxicity and volume of contaminants. These approaches may

be broken down into extractive and in situ methods. Extrac-

tive options involve the removal of contaminated soil, gener-

ally for treatment and disposal in an appropriate

landfill

for

incineration

where contaminants are broken down by

thermal oxidation. In situ processes treat the soil in-place.

In situ options include thermal, biological, and separation/

extraction technologies. Thermal technologies include ther-

mal desorption and in-place vitrification (glassification). Bi-

ological treatment includes biodegradation by soil

fungi

and

bacteria that ultimately renders contaminants into

carbon

dioxide

and water. This process is called mineralization.

Biodegradation may produce long-lived toxic intermediate

products. Separation technologies include soil vapor extrac-

Environmental Encyclopedia 3

Contaminated soil

tion for volatile organic compounds that removes a fraction

of the contaminants by enhancing volatilization by an in-

duced subsurface air flow; stabilization or chemical fixation

that uses additives to bind organics and

heavy metals

, thus

eliminating contaminated leachate; soil washing and flushing

using dispersants, solvents, or other means to solubilize cer-

tain contaminants such as PCBs and enhance their removal;

and finally, groundwater pump and treat schemes that purge

the contaminated soils with clean water in a flushing action.

The contaminated groundwater may then be treated by air

stripping, steam stripping,

carbon absorption

, precipita-

tion and flocculation and contaminant removal by

ion ex-

change

. A number of these approaches—in situ soil vitrifi-

cation and enhanced

bioremediation

using engineered

microorganisms—are experimental.

The number of potential remediation options is large

and expanding due to an active research program that is

driven by the need for low cost and more effective solutions.

The selection of an appropriate cleanup strategy for contami-

nated soils requires a thorough characterization of the site

and an analysis of the cost-effectiveness of suitable contain-

ment and treatment options. A site-specific analysis is re-

quired since the distribution and treatment of wastes may

be complicated by variation in geology, hydrology, waste

characteristics, and other factors at the site. Often, a demon-

stration of the effectiveness of an innovative or experimental

approach may be required by governmental authorities prior

to full scale implementation. In general, large sites use a

combination of remediation options. Pump and treat and

vapor extraction are the most popular technologies.

Cleanup costs and cleanup standards

The cleanup of contaminated soils can involve signifi-

cant expense and risk. In general, in situ containment is

cheaper than soil treatment, at least in the short run. While

the Superfund law establishes a preference for permanent

remedies, many cleanups that have been funded under this

law have used both containment and treatment options. In

general, in situ treatment methods such as groundwater

pump and treat are less expensive than extractive approaches

such as soil incineration. In situ options, however, may not

achieve cleanup goals. Like other processes, costs increase

with higher removal levels. Excavation and incineration of

contaminated soil can cost $1,500 per ton, leading to total

costs of many millions of dollars at large sites. Superfund

cleanups have averaged about $26 million (however, a sub-

stantial fraction of this is for site investigations). In contrast,

small fuel spills at

gasoline

stations may be mitigated using

vapor extraction at costs under $50,000.

Unlike air and water, which have specific federal laws

and regulations detailing maximum allowable levels of con-

taminants, no levels have been set for contaminants in soils.

Instead, the Environmental Protection Agency and states

316

A contour farm in southeastern Pennsylvania.

(Photograph by Jerry Irwin. Photo Researchers Inc. Repro-

duced by permission.)

use several approaches to set specific acceptable contaminant

levels. For Superfund sites, cleanup standards must exceed

applicable or relevant and appropriate requirements (AR-

ARs) under federal environmental and public health laws.

More generally, cleanup standards may be based on achieving