Environmental Encyclopedia

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Environmental Encyclopedia 3

Ethnobotany

from about three and a half million to over 15 million,

bringing with it an increase in

pollution

and

overfishing

of the bay.

Sewage treatment

plants contribute large

amounts of

phosphates

, while agricultural, urban, and sub-

urban discharges deposit

nitrates

, which in turn contribute

to algal blooms and oxygen depletion. Pesticides and indus-

trial toxics also contribute to the bay’s problems. Since the

early 1980s concerted efforts to clean up the Chesapeake Bay

and restore its seafood productivity have been undertaken by

state and federal agencies. Progress has been made but there

is still much to be done, both to restore this vital

ecosystem

and to insure prolonged cooperation between government

agencies, industry, and the general populace. See also Agricul-

tural pollution; Aquatic chemistry; Commercial fishing; Dis-

solved oxygen; Nitrates and nitrites; Nitrogen cycle; Restora-

tion ecology

[Eugene C. Beckham]

ESOURCES

OOKS

Baretta, J. W., and P. Ruardij, eds. Tidal Flat Estuaries. New York: Springer-

Verlag, 1988.

McLusky, D. The Estuarine Ecosystem. New York: Chapman & Hall, 1989.

ERIODICALS

Horton, T. “Chesapeake Bay: Hanging in the Balance.” National Geographic

183 (1993): 2–35.

Ethanol

Ethanol is an organic compound with the chemical formula

OH. Its common names include ethyl alcohol and

grain alcohol. The latter term reflects one method by which

the compound can be produced: the distillation of corn,

sugar cane, wheat and other grains. Ethanol is the primary

component in many alcoholic drinks such as beer, wine,

vodka, gin, and whiskey. Many scientists believe that ethanol

can and should be more widely used in automotive fuels.

When mixed in a one to nine ratio with

gasoline

, it is sold

gasohol

. The reduced costs of producing gasohol have

only recently made it a viable economic alternative to other

automotive fuels. See also Alternative fuels

Ethnobotany

The field of ethnobotany is concerned with the relationship

between indigenous cultures and plants. Plants play a major

and complex role in the lives of

indigenous peoples

, pro-

viding nourishment, shelter, and medicine. Some plants have

had such a major effect on traditional cultures that religious

527

ceremonies and cultural beliefs were developed around their

use. Ethnobotanists study and document these relationships.

The discovery of many plant-derived foods and medi-

cines first used by indigenous cultures has changed the mod-

ern world. On the economic side, the field of ethnobotany

determines the traditional uses of plants in order to find

other potential applications for food, medicine, and industry.

As an academic discipline, ethnobotany studies the interac-

tion between peoples and plant life to learn more about

human culture, history, and development. Ethnobotany

draws upon many academic areas including anthropology,

archeology, biology,

ecology

, chemistry, geography, history,

medicine, religious studies, and sociology to help understand

the complex interaction between traditional human cultures

and the plants around them.

Early explorers who observed how native peoples used

plants then carried those useful plants back to their own

cultures might be considered the first ethnobotanists, al-

though that is not a word they would have used to describe

themselves. The plant discoveries these explorers made

caused the expansion of trade between many parts of the

globe. For example, civilizations were changed by the discov-

ery and subsequent trade of sugar, tea, coffee, and spices

including cinnamon and black pepper.

During his 1492 voyage to the Caribbean, Christopher

Columbus discovered

tobacco

in Cuba and took it back

with him to Europe, along with later discoveries of corn,

cotton, and allspice. Other Europeans traveling to the Amer-

icas discovered tomatoes, potatoes, cocoa, bananas, pineap-

ples and other useful plants and medicines. Latex

rubber

was discovered in South America when European explorers

observed native peoples dipping their feet in the rubber

compound before walking across hot coals.

The study of plants and their place in culture has

existed for centuries. In India the vedas, which are long

religious poems that have preserved ancient beliefs for thou-

sands of years, contain descriptions of the use and value of

certain plants. Descriptions of how certain plants can be

used have been found in the ancient Egyptian scrolls. More

than 500 years ago the Chinese made records of medicinal

plants. In ancient Greece, Aristotle wrote about the uses of

plants in early Greek culture, and theorized that each plant

had a unique spirit. The Greek surgeon Dioscorides in

A.D.

77 recorded the medicinal and folk use of nearly 600 plants

in the Mediterranean region. During the Middle Ages, there

existed many accounts of the folk and medicinal use of plants

in Europe in books called herbals.

As the study of plants became more scientific, ethno-

botany evolved as a field. One of the most important contrib-

utors to the field was Carl Linnaeus, a Swedish botanist

who developed the system of naming organisms that is still

used today. This system of binomial classification gives each

Environmental Encyclopedia 3

Ethnobotany

organism a Latin genus and

species

name. It was the first

system that enabled scientists speaking different languages

to organize and accurately record new plant discoveries. In

addition to naming the 5,900 plants known to European

botanists, Linnaeus sent students around the world looking

for plants that could be useful to European civilization.

This was an early form of economic botany, an offshoot of

ethnobotany that is interested primarily in practical develop-

ments of new uses for plants. Pure ethnobotany is more

sociology-based, and is primarily interested in the cultural

relationship of plants to the indigenous peoples who use

them.

In the nineteenth century, bioprospecting, (the active

search for valuable plants in other cultures) multiplied as

exploration expanded across the globe. The most famous

ethnobotanist of the 1800s was Richard Spruce, an En-

glishman who spent 17 years in the Amazon living among

the native people and observing and recording their use of

plants. Observing a native treatment for fever, Spruce col-

lected cinchona bark from which the drug quinine was devel-

oped. Quinine has saved the lives of millions of people

infected with

malaria

. Spruce also documented the native

use of hallucinogenic plants used in religious rituals and the

accompanying belief systems associated with these halluci-

nogenic plants.

Many native cultures on all continents believed that

certain psychoactive plants that caused visions or hallucina-

tions gave them access to spiritual and healing powers.

Spruce discovered that for some cultures, plants were central

to the way human life and the world was perceived. Thus,

the field of ethnobotany began expanding from the study of

the uses of plants to how plants and cultures interacted on

more sociological or philosophical/religious grounds.

An American botanist named John Harshberger first

coined the term “ethnobotany” in 1895, and the field evolved

into an academic discipline in the twentieth century. The

University of New Mexico offered the first master’s degree

in ethnobotany. Their program concentrated on the ethno-

botany of the Native Americans of the southwestern United

States.

In the twentieth century one of the most famous eth-

nobotanists and plant explorers was Harvard professor Rich-

ard Evans Schultes. Inspired by the story of Richard Spruce,

Schultes lived for 12 years with several indigenous tribes in

South America while he observed and documented their use

of plants as medicine, poison, and for religious purposes.

He discovered many plants that have been investigated for

pharmaceutical use. His work also provided further insight

into the use of hallucinogenic plants by native peoples and

the cultural significance of that practice.

Interest in ethnobotany increased substantially in the

1990s. One study showed that the number of papers in the

528

field doubled in the first half of the 1990s, when compared

to the last half of the 1980s. By the early 2000s, several

universities around the world offered graduate programs in

ethnobotany, and undergraduate programs were becoming

more common. By the start of twenty-first century, ethnobo-

tany was an accepted academic field. In addition, the phar-

maceutical industry continued to research plants used by

indigenous cultures in a quest for new or more effective

drugs.

Many countries conduct ethnobotanical studies of

their native cultures. A research survey showed that nearly

40% of ethnobotanical studies are being conducted in North

America, but other countries including Brazil, Columbia,

Germany, France, England, India, China, and Kenya, are

also active in the field. For instance, ethnobotanists in China

and India are recording traditional medicine systems that

use native plants. Researchers are also studying traditional

sustainable agriculture

methods in Africa in the hope of

applying them to new drought-management techniques.

Interest in the field of ethnobotany has increased as

scientists have learned more about indigenous cultures.

“Primitive” people were once viewed as backward and lacking

in knowledge compared to the “civilized” world, but ethno-

botanists and other scientists have shown that native peoples

often have developed sophisticated knowledge about prepar-

ing and using plants for food and medicine.

The ways in which people and plants interact are broad

and complex, and the modern field of ethnobotany, in its

many areas of inquiry, reflects this complexity. Areas of

interest to ethnobotanists include traditional peoples’ knowl-

edge and interaction with plant life, traditional agricultural

practices, indigenous peoples’ conception of the world

around them and the role of plants in their religious belief

systems and rituals, how plants are used to make products

and art objects, the knowledge and use of plants for medicine

(a sub-field called ethnopharmacology), and the historical

relationship between plants and past peoples (a sub-field

called paleoethnobotany).

At the beginning of the twenty-first century, ethnobo-

tanists are fighting a war against time, because the world’s

native cultures and stores of plant life are disappearing at a

rapid pace. Language researchers have estimated that the

world lost over half of its spoken languages in the twentieth

century, and of the languages that remain, only 20% were

being taught to young children in the early 2000s. The loss

of traditional languages indicates that indigenous cultures

are disappearing quickly as well. Historically, up to 75% of

all useful plant-derived compounds have been discovered

through the observation of folk and traditional plant use.

Ethnobotanists are concerned that modern people will lose

a storehouse of valuable plant knowledge, as well as rare

Environmental Encyclopedia 3

Eurasian milfoil

cultural and historical information, as these indigenous cul-

tures disappear.

Ethnobotanists, like many scientists, are concerned

about environmental devastation from development pressure

and slash-and-burn agriculture in less developed regions that

are rich and diverse in plant life, such as the Amazon rainfor-

est. Harvard biologist E. O. Wilson has estimated that the

world is losing as many as 74 species per day. To put ethno-

botanists’ concerns about forest loss in perspective, a single

square kilometer of rainforest may contain more plant species

than an area in North America equaling size of Vermont.

And, of all the plant species in the rainforest, fewer than

1% have been scientifically analyzed for potential uses. Con-

sidering that 25% of all prescription drugs in the United

States contain active ingredients derived from plants, the

continuing loss of the world’s plant communities could be

an incalculable loss.

In the face of disappearing indigenous peoples and the

loss of botanically rich

habitat

, ethnobotanists must work

quickly. Active areas in the field of ethnobotany in the early

2000s include the identification of new plant-derived foods,

fibers and pharmaceuticals, investigation of traditional ag-

ricultural methods and vegetation management, using tradi-

tional technologies for

sustainable development

, and the

deeper understanding of ecology and ways to preserve the

biodiversity

of ecosystems.

[Douglas Dupler]

ESOURCES

OOKS

Cotton, C. M. Ethnobotany: Principles and Applications. New York: John

Wiley & Sons, 1996.

Davis, Wade. Light at the Edge of the World: A Journey Through the Realm of

Vanishing Cultures. Washington, DC: National Geographic Society, 2001.

Moerman, Daniel E. Native American Ethnobotany. Portland, OR: Timber

Press, 1998.

Plotkin, Mark J. Tales of a Shaman’s Apprentice: An Ethnobotanist Searches

for New Medicines in the Amazon Rainforest. New York: Viking, 1993.

Schultes, Richard Evans, and Albert Hoffman. Plants of the Gods. Rochester,

VT: Healing Arts Press, 1992.

Schultes, Richard Evans, and Siri von Reis, eds. Ethnobotany: Evolution of

a Discipline. Portland, OR: Dioscorides Press, 1995.

Wilson, E. O. Biophilia. Cambridge: Harvard University Press, 1984.

ERIODICALS

Cox, Paul Alan. “Carl Linnaeus: The Roots of Ethnobotany.” Odyssey

(February 2001): 6.

Magee, Bernice E. “Hunting for Poisons.” Appleseeds, April 2001, 20.

THER

Society for Economic Botany Home Page. [cited July 2002]. <http://www.econ-

bot.org>.

529

see

European Union

Eurasian milfoil

Eurasian milfoil (Myriophyllum spicatum) is a feathery-look-

ing underwater plant that has become a major nuisance in

waterways in the United States. Introduced into the country

over 70 years ago as an ornamental tank plant by the aquar-

ium industry, it has since spread to the East Coast from

Vermont to Florida and grows as far west as Wisconsin

and Texas. It is also found in California. It is particularly

abundant in the

Chesapeake Bay

, the Potomac River, and

in some Tennessee Valley reservoirs.

Eurasian milfoil is able to tolerate a wide range of

salinity

in water and grows well in inland fresh waters as

well as in

brackish

coastal waters. The branched stems grow

from 1–10 ft (0.3–3 m) in length and are upright when

young, becoming horizontal as they get older. Although

most of the plant is underwater, the tips of the stems often

project out at the surface. Where the water is hard, the stems

may get stiffened by calcification. The leaves are arranged

in whorls of four around the branches with 12–16 pairs of

leaflets per leaf. As with other milfoils, the red flowers of

Eurasian milfoil are small and inconspicuous. As fragments

of the plant break off, they disperse quickly through an

area, with each fragment capable of putting out roots and

developing into a new plant. Due to its extremely dense

growth, Eurasian milfoil has become a nuisance that often

impedes the passage of boats and vessels along navigable

waterways. It can cause considerable damage to underwater

equipment and lead to losses of time and money in the

maintenance and operation of shipping lanes. It also inter-

feres with recreational water uses such as fishing, swimming,

and diving. In the

prairie

lakes of North Dakota, the woody

seeds of this plant are eaten by some waterfowl such as

ducks. However, this plant appears to have little

wildlife

value, although it may provide some cover to fishlife.

Aquatic weed control

experts recommend that ves-

sels that have passed through growths of Eurasian milfoil

be examined and plant fragments removed. They also advo-

cate the physical removal of plant growths from shorelines

and other areas with a high potential for dispersal. Addition-

ally, chemical agents are also often used to control the weed.

Some of the commonly used herbicides include

2,4-D

and

Diquat. These are usually diluted with water and applied at

the rate of one to two gallons per acre. The application of

herbicides to control aquatic weed growth is regulated by

environmental agencies due to the potential of harm to non-

target organisms. Application times are restricted by season

and duration of exposure and depend on the kind of

herbi-

Environmental Encyclopedia 3

European Union

cide

used, its mode of action, and its impacts on the other

biota in the aquatic system. See also Aquatic chemistry; Com-

mercial fishing

[Usha Vedagiri]

ESOURCES

OOKS

Gunner, H. B. Microbiological Control of Eurasian Watermilfoil. Washington,

DC: U.S. Army Engineer Waterways Experiment Station, 1983.

Hotchkiss, N. Common Marsh Underwater and Floating-Leaved Plants of

the United States and Canada. Mineola, NY: Dover Publications, 1972.

Schmidt, J. C. How to Identify and Control Water Weeds and Algae. Milwau-

kee, WI: Applied Biochemists, Inc., 1987.

European Economic Community (EEC)

see

European Union

European Greens

see

Green politics

European Union

The European Union (EU) is a political and monetary orga-

nization of European nations. Its members as of 2002 were

Austria, Belgium, Denmark, Finland, France, Germany,

Greece, Ireland, Italy, Luxembourg, the Netherlands, Portu-

gal, Spain, Sweden, and the United Kingdom. While mem-

ber states retain their national governments, the EU promul-

gates transnational laws and treaties, has a unified

agricultural policy, and has removed trade barriers between

members. The EU uses a common currency, the euro. The

EU represents about a quarter of the global economy, roughly

equal to that of the United States.

The European Union developed gradually in the years

after World War II. It began in 1957 as the European

Economic Community, or EEC, which originally included

France, West Germany, Italy, Belgium, the Netherlands,

and Luxembourg. The EEC was superceded by the Euro-

pean Community, or EC, in 1967. The principal aim of

the EC was to foster free trade among member countries,

eliminating tariffs and customs barriers. The EC expanded

its role in the 1970s and 1980s. As more states joined,

the EC began to strengthen political cooperation among

members, holding meetings to coordinate foreign policy and

international law. By the mid-1980s, plans were underway

to transform the EC into a single European market. This

single market would have a central banking system, a trans-

national currency, and a unified foreign policy. These goals

were articulated in the Single European Act of 1987, which

530

also for the first time set out environmental protection as

an important goal of European economic development. A

treaty written in 1991, called the Maastricht Treaty or the

Treaty on European Union, spelled out the future shape of

the European Union. All the member states had ratified

the treaty by November, 1993, when the European Union

officially superceded the EC. The EU went on to launch a

new currency, the euro, in 1999. In January 2002 the euro

replaced existing EU member currencies.

The EU had incorporated

environmental policy

into

its economic plans beginning in 1987. New members were

required to conform to certain environmental standards. And

the EU was able to make regional environmental policy,

which often made more sense than national laws for prob-

lems like air and

water pollution

that extended across na-

tional borders. Environmental regulation in the EU was

generally stricter than in the United States, though member

states did not always comply with the law. The EU was

often quicker than the United States on implementing envi-

ronmental strategy, such as rules for computer and cell phone

disposal. The EU approved the 1997 Kyoto Protocol, an

international agreement to reduce the production of so-

called

greenhouse gases

in order to arrest global warming.

As details of the implementation of the plan were being

worked out over the next five years, EU negotiators remained

committed to curtailing European gas emissions even after

it became clear that the United States would not sign the

Kyoto treaty. Sweden took over the rotating presidency of

the EU in 2002, and planned to make environmental policy

a high priority. “The

environment

is more global than

anything else except foreign policy,” Sweden’s environmental

minister and EU spokesman told Harper’s Bazaar (March

2001). With the EU representing 25% of the global econ-

omy, the organization’s stance on environmental issues was

always significant.

[Angela Woodward]

ESOURCES

ERIODICALS

Andrews, Edmund L. “Bush Angers Europe by Eroding Pact on Warming”-

New York Times, April 1, 2001, 3.

Milmo, Sean. “EU Lacks Industry Support for EU-Wide Emissions Trad-

ing System.” Chemical Market Reporter 260, no. 5 (July 30, 2001): 6.

Sains, Ariane. “EU News: Sweden’s EU Agenda.” Harper’s Bazaar 134,

no. 3472 (March 2001): 287.

Scott, Alex. “EU Mulls Criminal Sanctions for Eco-Crimes.” Chemical

Week 164, no. 16 (April 17, 2002): 15.

“What Next, Then?” Economist 360, no. 8232 (July 28, 2001): 69.

Environmental Encyclopedia 3

Everglades

Eutectic

Refers to a type of solar heating system which makes use of

phase changes in a chemical storage medium. At its melting

point, any chemical compound must absorb a quantity of

heat in order to change phase from solid to liquid, and at

its boiling point, it must absorb an additional quantity of

heat to change to a gas. Conversely, a compound releases a

quantity of heat when condensing or freezing. Therefore, a

chemical warmed by

solar energy

through a phase change

releases far more energy when it cools than, for example,

water heated from a cool liquid to a warm liquid state.

For this reason, solar heating systems that employ phase-

changing

chemicals

can store more energy in a compact

space than a water-based system.

Eutrophication

see

Cultural eutrophication

Evapotranspiration

Evapotranspiration is a key part of the

hydrologic cycle

Some water evaporates directly from soils and water bodies,

but much is returned to the

atmosphere

transpiration

(a word combining transport and evaporation) from plants

via openings in the leaves called stomata. Within the same

climates, forests and lakes yield about the same amount of

water vapor. The amount of evapotranspiration is dependent

on energy inputs of heat, wind, humidity, and the amount

of stored

soil

water. In

climate

studies this term is used to

indicate levels of surplus or deficit in water budgets. Aridity

may be defined as an excess of potential evapotranspiration

over actual precipitation, while in humid regions the amount

runoff

correlates well with the surplus of precipitation

over evapotranspiration.

Everglades

A swampy region in southern Florida, the Everglades are

described as a vast, shallow sawgrass (Cladium effusum) marsh

with tree islands, wet prairies, and aquatic sloughs, the Ever-

glades historically covered most of southeastern Florida,

prior to massive

drainage

and

reclamation

projects

launched at the turn of the century. The glades constitute

the southern end of the Kissimmee Lake Okeechobee Ever-

glades system, which encompasses most of south and central

Florida below Orlando. Originally, the Everglades covered

an area approximately 40 mi (64 km) wide and 100 mi (161

km) long, or 2.5 million acres, but large segments have been

isolated by canals and levees. Today, intensive agriculture

531

in the north and rapid urban development in the east are

among the Everglades’ various land uses.

Two general

habitat

regions can be demarcated in

the Everglades. The first includes three

water conservation

areas, basins created to preserve portions of the glades and

provide multiple uses, such as water supply. This region is

located in the northern Everglades and contains most of the

intact natural marsh. The second is the southern habitat,

which includes the Everglades

National Park

and the

southern third of the three water

conservation

areas. The

park has been designated a World Heritage Site of interna-

tional ecological significance, and the Everglades as a whole

are one of the outstanding freshwater ecosystems in the

United States.

Topographically flat, elevations in the Everglades are

generally less than 20 ft (6.1 m). The ground slopes north

to south at an average gradient of 0.15 ft per mile, with the

highest elevations in the north and the lowest in the south.

The

climate

is generally subtropical, with long, hot, humid,

and wet summers from May to October followed by mild,

dry winters from November to April. During the wet season

severe storms can result in lengthy periods of

flooding

, while

during the dry season cool, sometimes freezing temperatures

can be accompanied by thunderstorms, tornadoes, and heavy

rainfall.

Before the Everglades were drained, large areas of

the system were inundated each year as Lake Okeechobee

overflowed its southern rim. The “River of Grass” flowed

south and was in constant flux through

evapotranspira-

tion

, rainfall, and water movement into and out of the Ever-

glades’

aquifer

. The water discharged into the tidewaters

of south Biscayne Bay, Florida Bay, and Ten Thousand

Islands.

In the early 1880s, Philadelphia industrialist Hamilton

Disston began draining the Everglades under a contract with

Florida trustees. Disston, whose work ceased in 1889, built

a substantial number of canals, mainly in the upper waters

of the Kissimmee River, and constructed a canal between

Lake Okeechobee and the Calooshatchee River to provide

an outlet to the Gulf of Mexico. The Miami River was

channelized beginning in 1903, and other canals—the Snap-

per Creek Canal, the Cutler Canal, and the Coral Gables

Waterway—were opened to help drain the Everglades.

Water tabless in south Florida fell 5–6 ft (1.5–1.8 m) below

1900 levels, causing stress to

wetlands

systems and losses

of peat up to 6 ft (1.8 m) in depth.

Full-scale drainage and reclamation occurred under

Governor W.S. Jennings (1901–1905) and Governor Napo-

leon Bonaparte Broward (1905–1909). In 1907, the Ever-

glades Drainage District was created and built six major

canals over 400 miles long before it suffered financial collapse

in 1928. These canals enabled agriculture to flourish within

Environmental Encyclopedia 3

Everglades

the region. In the late 1920s, when settlers realized better

water control and flood protection were needed, low muck

levees were built along Lake Okeechobee’s southwest shore,

eliminating the lake’s overflow south to the Everglades. But

hurricanes in 1926 and 1928 breached the levees, destroying

property and killing 2,100 people. As a result, the Lake

Okeechobee Flood Control District was established in 1929,

and over the following fifteen years the United States

Army

Corps of Engineers

constructed and enlarged flood control

canals.

It was only in the mid-1950s, with the development

and implementation of the Central and Southern Florida

Project for Flood Control & Other Purposes (C&SF Proj-

ect), that water control took priority over uncontrolled drain-

age of the Everglades. The project, completed by 1962, was

to provide flood protection, water supply, and environmental

benefits over a 16,000 square-mile (41,440 sq-km) area. It

consists of 1,500 miles (2,415 km) of canals and levees, 125

major water control structures, 18 major pumping stations,

13 boat locks, and several hundred smaller structures. Inter-

spersed throughout the Everglades is a series of habitats,

each dominated by a few or in some cases a single plant

species

. Seasonal wetlands and upland pine forests, which

once dominated the historic border of the system, have come

under the heaviest pressure from urban and agricultural de-

velopment. In the system’s southern part, freshwater wet-

lands are superseded by muhly grass (Muhlenbergia filipes),

prairies, upland pine and tropical hardwood forests, and

mangrove forests that are influenced by the tides.

Attached algae, also known as periphyton, are an im-

portant component of the Everglades food web, providing

both organic food matter and habitat for various grazing

invertebrates and forage fish that are eaten by wading birds,

reptiles, and sport fish. These algae include calcareous and

filamentous algae (Scytonema hoffmani, Schizothrix calcicola)

and diatoms (Mastogloia smithii v. lacustris).Sawgrass (Clad-

ium jamaicense) constitutes one of the main plants occurring

throughout the Everglades, being found in 65–70% of the

remaining freshwater marsh. In the north, the sawgrass

grows in deep

peat soils

and is both dense and tall, reaching

up to 10 ft (3 m) in height. In the south, it grows in low-

nutrient

marl soils and is less dense and shorter, averaging

2.5–5 ft (0.75–1.5 m). Sawgrass is adapted to survive both

flooding and burning. Stands of pure sawgrass as well as

mixed communities are found in the Everglades. The mixed

communities can include maidencane (Panicum hemitomon)

arrowhead (Sagittaria lancifolia), water hyssop (Bacopa carol-

iniana), and spikerush (Eleocharis cellulosa).

Wet prairies, which together with aquatic sloughs pro-

vide habitat during the rainy season for a wide variety of

aquatic invertebrates and forage fish, are another important

habitat of the Everglades system. They are seasonally inun-

532

dated wetland communities that require certain standing

water for six to ten months. Once common, today more

than 1,500 square miles (3,885 sq km) of these prairies have

been drained or destroyed. The lowest elevations of the

Everglades are ponds and sloughs, which have deeper water

and longer inundation periods. They occur throughout the

system, and in some cases can be formed by alligators in

peat soils. Among the types of emergent vegetation com-

monly found in these areas are white water lily (Nymphaea

odorata), floating heart (Nymphoides aquatica), and spatter-

dock (Nuphar luteum). Common submerged species include

bladderwort (Utricularia) and the periphyton mat commu-

nity. Ponds and sloughs serve as important feeding areas

and habitat for Everglades

wildlife

At the highest elevations are found communities of

isolated trees surrounded by marsh called tree islands. These

provide nesting and roosting sites for colonial birds and

habitat for deer and other terrestrial animals during high-

water periods. Typical dominant species constituting tree

islands are red bay (Persa borbonia), swamp bay (Magnolia

virginiana), dahoon holly (Ilex cassine), pond apple (Annona

glabra), and wax myrtle (Myrica cerifera). Beneath the canopy

grows a dense shrub layer of cocoplum (Chrysobalanus icacao),

buttonbush (Cephalanthus accidentalis), leather leaf fern

(Acrostichum danaeifolium), royal fern (Osmunda regalis), cin-

namon fern (O. cinnamonea), chain fern (Anchistea virginica),

bracken fern (Pteridium aquilinium), and lizards tail (Saur-

urus cernuus).

In addition to the indigenous plants of the Everglades,

numerous exotic and nuisance species have been brought

into Florida and have now spread in the wild. Some threaten

to invade and displace indigenous species. Brazilian pepper

(Schinus terebinthifolius), Australian pine (Casuarina equiseti-

folia), and melaleuca (Melaleuca quinquenervia) are three of

the most serious

exotic species

that have gained a foothold

and are displacing native plants.

The Florida Game and Fresh Water Fish Commission

has identified 25 threatened or endangered species with the

Everglades. Mammals include the

Florida panther

(Felis

concolor coryi), mangrove fox squirrel (Sciurus niger avicennia),

and black bear (Ursus americanus floridanus). Birds include

the wood stork (Mycteria americana), snail kite (Rostrhamus

sociabilis), and the red-cockaded (Picoides borealis). Endan-

gered or threatened reptiles and amphibians include the

gopher tortoise (Gopherus polyphemus the eastern indigo

snake (Drymarchon corais couperi), and the loggerhead

sea

turtle

(Caretta caretta).

The alligator (Alligator mississippiensis) was once en-

dangered due to excessive alligator hide

hunting

. In 1972,

the state made alligator product sales illegal. Protection al-

lowed the species to recover, and it is now widely distributed

in wetlands throughout the state. It is still listed as threatened

Environmental Encyclopedia 3

Evolution

A swampy area in the Everglades. (Photograph

by Gerald Davis. Phototake. Reproduced by permission.)

by the federal government, but in 1988 Florida instituted

an annual alligator harvest.

Faced with pressures on Everglades habitats and the

species within them, as well as the need for water manage-

ment within the rapidly developing state, in 1987 the Florida

legislature passed the Surface Water Improvement and Man-

agement Act (1987). The law requires the state’s five water

management districts to identify areas needing preservation

or restoration. The Everglades Protection Area was identi-

fied as a priority for preservation and improvement planning.

Within the state’s protection plan, excess nutrients, in large

part from agriculture, have been targeted as a major problem

that causes natural periphyton to be replaced by species more

tolerant of

pollution

. In turn, sawgrass and wet

prairie

communities are overrun by other species, impairing the

Everglades’ ability to serve as habitat and forage for higher

trophic level

species.

A federal lawsuit was filed against the South Florida

Management District in 1988 for

phosphorus

pollution,

and in 1989, President George Bush authorized the addition

of more than 100,000 acres to the Everglades National Park.

The law that authorized this addition was Public Law 101-

229 or the Everglades National Park Protection and Expan-

sion Act of 1989. Included in this legislation was the stipula-

tion that the Army Corps of Engineers improve water flow

533

to the Park. In 1994, the Everglades Forever Act was passed

by the Florida State Legislature. The Act called for construc-

tion of experimental marshes called Stormwater Treatment

Areas that were designed to remove phosphorus from water

entering the Everglades. In 1997, six more Stormwater

Treatment Areas were constructed and

phosphorus re-

moval

was estimated to be as much as 50%, due in part to

better management practices that were mandated by the

Everglades Forever Act. In 2000, President Clinton author-

ized the spending of billions of federal dollars to restore the

Everglades, while Florida Governor Jeb Bush agreed to a

state commitment of 50% of the cost, in a bill called the

Florida Investment Act. In 2001 and 2002, the state of

Florida, under Governor Jeb Bush, and the federal govern-

ment, under President George W. Bush, committed $7.8

billion dollars to implement the Comprehensive Everglades

Restoration Plan (CERP).

[David Clarke and Marie H. Bundy]

ESOURCES

OOKS

Douglas, M. S. The Everglades: River of Grass. New York: H. Wolff, 1947.

ERIODICALS

Johnson, R. “New Life for the ’River of Grass.’” American Forests 98 (July-

August 1992): 38–43.

Stover, D. “Engineering the Everglades.” Popular Science 241 (July 1992):

46–51.

Evolution

Evolution is an all-pervading concept in modern science

applied to physical as well as biological processes. The phrase

theory of evolution, however, is most commonly associated

with organic evolution, the origin and evolution of the enor-

mous diversity of life on this planet.

The idea of organic evolution arose from attempts to

explain the immense diversity of living organisms and dates

from the dawn of culture. Attempts to formulate a naturalis-

tic explanation of the phenomena of evolution in one form or

another had been proposed, and by the end of the eighteenth

century a number of naturalists from Carolus Linnaeus to

Jean-Baptiste Lamarck had questioned the prevailing doc-

trine of fixity of

species

. Lamarck came the closest to pro-

posing a complete theory of evolution, but for several reasons

his theory fell short and was not widely accepted.

Two English naturalists conceived the first truly com-

plete theory of evolution. In a most remarkable coincidence,

working quite independently, Charles Darwin and Alfred

Russell Wallace arrived at essentially the same thesis, and

their ideas were initially publicized jointly in 1858. However,

Environmental Encyclopedia 3

Evolution

it is to Charles Darwin that the recognition of the founder

of modern evolution is attributed. His continued efforts

toward a detailed development of the evidence and the expli-

cation of a complete, convincing theory of organic evolution

resulted in the publication in 1859 of his book On the Origin

of Species by Natural Selection. With the publication of this

volume, widely regarded as one of the most influential books

ever written, regardless of subject matter, the science of

biology would never be the same.

Darwin was the first evolutionist whose theories car-

ried conviction to a majority of his contemporaries. He set

forth a formidable mass of supporting evidence in the form

of direct observations from

nature

, coupled with a compre-

hensive and convincing synthesis of current knowledge.

Most significantly, he proposed a rational, plausible instru-

mentality for evolutionary change: natural selection.

The theory Darwin presented is remarkably simple

and rational. In brief, the theoretical framework of evolution

presented by Darwin contained three basic elements. First

is the existence of variation in natural populations. In nature

there are no individuals who are exactly alike, therefore

natural populations always consist of members who all differ

from one another to some degree. Many of these differences

are heritable and are passed on from generation to genera-

tion. Second, some of these varieties are better adapted to

their

environment

than others. Third, the reproductive po-

tential of populations is unlimited. All populations have the

capacity to overproduce, but populations in nature are limited

by high

mortality

. Thus, if all offspring cannot survive

each generation, the better-adapted members have a greater

probability

of surviving each generation than those less

adapted.

Thomas Henry Huxley, when first presented with

Darwin’s views, was supposed to have exclaimed: “How ex-

tremely stupid not to have thought of that.” This apocryphal

statement expresses succinctly the immediate intelligibility

of this momentous discovery.

Darwin’s theory as presented was incomplete, as he

was keenly aware, but the essential parts were adequate at

the time to demonstrate that the material causes of evolution

are possible and can be investigated scientifically.

One of the most critical difficulties with Darwin’s

theory was the inability to explain the source of hereditary

variations observed in populations and, in particular, the

source of hereditary innovations which, through the agency

of natural selection, could eventually bring about the trans-

formation of a species. The lack of existing knowledge of

the mechanism of heredity in the mid-1800s precluded a

scientifically sound solution to this problem.

The re-discovery in 1900 of Gregor Mendel’s experi-

ments demonstrating the underlying process of inheritance

did not at first provide a solution to the problem facing

534

Darwinian evolutionary theory. In fact, in one of the most

extraordinary paradoxes in the history of science, during the

first decades of Mendelian genetics, a temporary decline

occurred in the support of Darwinian selectionism. This was

primarily because of the direction and level of research as

much as the lack of knowledge in further details of the

underlying mechanisms of inheritance.

It was not until the publication of Theodosius Dobz-

hansky’s Genetics and the Origin of Species (1937) that the

modern synthetic theory of evolution began to take form,

renewing confidence in selectionism and the Darwinian

theory. In his book, Dobzhansky, for the first time, inte-

grated the newly developed mathematical models of popula-

tion genetics with the fats of chromosomal theory and

muta-

tion

together with observations of variation in natural

populations.

Dobzhansky also stimulated a series of books by several

major evolutionists which provided the impetus and direc-

tion of research over the next decade, resulting in a reformu-

lation of Darwin’s theory. This became known as the synthetic

theory of evolution. Synthetic is used here to indicate that

there has been a convergence and synthesis of knowledge

from many disciplines of biology and chemistry.

The birth of molecular genetics in 1950 and the enor-

mous expansion of knowledge in this area have affected the

further development and refinement of the synthetic theory

markedly. But it has not altered the fundamental nature

of the theory. Darwin’s initial concept in this expanded,

modernized form has taken on such stature as to be generally

considered as the most encompassing theory in biology. To

the majority of biologists, the synthetic theory of evolution

is a grand theory that forms the core of modern biology. It

also provides the theoretical foundation upon which most

all other theories find support and comprehension. Or, as

the distinguished evolutionary biologist Dobzhansky so suc-

cinctly put it: “Nothing in life makes sense except in the

light of evolution.”

If the three main elements of the Darwinian theory

were to be restated in terms of the modern synthetic theory,

they would be as follows. First, genetic systems governing

heredity in each organism are composed of genes and chro-

mosomes which are discrete but tightly interacting units of

different levels of complexity. The genes, their organized

associations in chromosomes, and whole sets of chromo-

somes, have a large degree of

stability

as units. But these

units are shuffled and combined in various ways by sexual

processes of reproduction in most organisms. The result of

this process, called recombination, maintains a considerable

amount of variation in any population in nature without

introducing any new hereditary factors. Genetic experimen-

tation, is, in fact, occurring all the time in natural popula-

tions. Each generation, as a result of recombination, is made

Environmental Encyclopedia 3

Evolution

up of members who carry different hereditary combinations

drawn from the common pool of the population. Each mem-

ber generation in turn interacts within the same environmen-

tal matrix which, in effect, “tests” the fitness of these heredi-

tary combinations. The sole source of hereditary innovation

from within the population, other than recombination,

would come from mutation affecting individual genes, chro-

mosomes or sets of chromosomes, which are then fed into

the process of recombination.

Second, populations of similar animals—members of

the same species—usually interbreed among themselves

making up a common pool of genes. The gene pools of

established populations in nature tend to remain at equilib-

rium from generation to generation. An abundance of evi-

dence has established the fact, as Darwin and others before

him had observed, that populations have greater reproductive

capacity than they can sustain in nature.

Third, change, over time, in the makeup of the

gene

pool

, may occur by one of four known processes: mutation,

fluctuation in gene frequencies—known as “sampling errors,”

or “genetic drift,” which is generally effective only in small,

isolated populations—introduction of genes from other pop-

ulations, and differential reproduction.

The first three of these processes do not produce adap-

tive trends. These are essentially random in their effects,

usually nonadaptive and only rarely and coincidentally pro-

duce

adaptation

. Of the four processes, differential repro-

duction results in adaptive trends. Differential reproduction

describes the consistent production of more offspring, on

an average, by individuals with certain genetic characteristics

than those without those characteristics. This is the modern

understanding of natural selection, with emphasis upon suc-

cess in reproduction. The Darwinian and Neo-Darwinian

concepts, on the other hand, placed greater emphasis upon

“survival of the fittest” in terms of mortality and survival.

Natural selection, in the Darwinian sense, was non-random

and produced trends that were adaptive. Differential repro-

duction produces the same result. In what may appear to be

a paradox, differential selection also acts in stabilizing the

gene pool by reducing the reproductive success of those

members whose hereditary variation result in non-adap-

tive traits.

As Darwin first recognized, the link between variabil-

ity or constancy of the environment and evolutionary change

or stability is provided by natural selection. The interaction

between organisms and their environment will inevitably

affect the genetic composition of each new generation. As

a result of differential selection, the most fit individuals, in

terms of reproductive capacity, contribute the largest propor-

tion of genes or alleles to the next generation. The direction

in which natural selection guides the population depends

535

upon both the nature of environmental change or stability

and the content of the gene pool of the population.

From the very beginning, evolutionists have recog-

nized the significance of the environment/evolution linkage.

This linkage always involves the interactions of a great many

individuals both within populations of a single species (intra-

specific) and among members of different species (interspe-

cific linkage). These are inextricably linked with changes in

the physical environment.

Dobzhansky estimated that the world may contain

four to five million different kinds of organisms, each ex-

ploiting in various ways a large number of habitats. The

complexity of ecosystems is based upon thousands of differ-

ent ways of exploiting the same habitats in which each species

is adapted to its specifically defined

niche

within the total

habitat

. The diversity of these population-environment in-

teractions is responsible for the fact that natural selection can

be conservative—(normalizing selection)—and can promote

constancy in the gene pool. It directs continuous change

(directional selection), or promotes diversification into new

species (diversifying selection).

Recent trends in research have been of special signifi-

cance in understanding the dynamics of these processes.

They have greatly increased the body of information related

to the ecological dimension of

population biology

. These

studies have developed methods of analysis and sophisticated

models which have made major advances in the study and

understanding of the nature of the selective forces that direct

evolutionary change. It is increasingly clear that a reciprocal

imperative exists between ecological and environmental

studies to further our understanding of the role of evolution-

ary and counterrevolutionary processes affecting stability in

biological systems over time. The urgency of the need for

an expanded synthesis of ecological and evolutionary studies

is driven by the accelerating and expanding counterrevolu-

tionary changes in the world environment resulting from

human actions.

Evolutionary processes are tremendously more com-

plex in detail than this brief outline suggests. This spare

outline, however, should be sufficient to show that here

is a mechanism, involving materials and processes known

beyond doubt to occur in nature, capable of shaping and

changing species in response to the continuously dynamic

universe in which they exist.

[Donald A. Villeneuve]

ESOURCES

OOKS

Dobzhansky, T., et al. Evolution. San Francisco: W. H. Freeman, 1977.

Simpson, G. G. The Meaning of Evolution. New Haven, CT: Yale University

Press, 1967.

Environmental Encyclopedia 3

Exclusive economic zone

The Exclusive Economic Zone (EEZ) is a 200-mile bound-

ary off the coasts of a nation that provides the exclusive right

to fish, mine, and otherwise utilize the

natural resources

located within the zone. After World War II, many nations

became concerned about the intrusion of foreign fishing

vessels into the rich and productive waters off of their coasts.

The 1958 Convention on Fishing and Conservation of Liv-

ing Resources of the High Seas, established rules that al-

lowed a coastal nation impose terms on the uses of natural

resources of their coastal oceans. This effort at regulation

was unsuccessful, and the rules were never put in place. The

policy that ultimately established exclusive economic zones

around sovereign nations resulted from provisions of the

Third United Nations Conference on the Law of the Sea,

held in 1973. As a result of the actions taken in 1958,

virtually all of the world’s fisheries are controlled by one

nation or another. However, the controlling nation must

provide access to the resources that it cannot harvest, and

is responsible for preventing

pollution

and depletion of the

resources in the waters that it controls. In the United States,

the Fishery Conservation and Management Act of 1976

established the fishery conservation zone out to 200 miles,

however, it wasn’t until 1983 that the EEZ was created by

presidential proclamation.

[Marie H. Bundy]

Existence value

see

Debt for nature swap

Exotic species

Exotic

species

are organisms that are introduced to a region

ecosystem

, often unintentionally, through human

mi-

gration

or trade. Some exotic species are useful to man,

such as horses, goats, pigs, and edible plants including wheat

and oats. These are examples of species that were brought

to the Americas intentionally by European colonists. Other

exotic species that were introduced accidentally such as the

Mediterranean fruit fly

(Ceratitis capitata), Japanese beetle

(Popillia japonica),

Africanized bees

(Apis mellifera scutel-

lata)(sometimes called killer bees), and Norway rat (Rattus

norvegicus) have become pests. Many exotic species, includ-

ing most tropical fish, birds, and houseplants brought to

colder climates, can survive only under continuous care. A

few prove extremely adaptable and thrive in their new

envi-

ronment

, sometime becoming invasive and out competing

native species.

536

The federal government’s Office of Technology As-

sessment has estimated that more than 2,000 plant species

introduced from around the world currently live and thrive

in the United States, and that 15 of these have caused more

than $500 million worth of damage. Economic costs associ-

ated with exotic species include agricultural losses, damage

to infrastructure, as when aquatic plants clog water intakes,

and the costs of attempts to restore native species whose

survival is endangered by

introduced species

Exotic species are most are most destructive when

they adapt readily to their new environment and compete

successfully with native species. Unfortunately there is no

sure way to know which introduced species will become

invasive. Often these plant and animals turn out to be better

competitors because, unlike native species, they have no

natural pests,

parasites

, diseases, or predators in their new

home.

Purple loosestrife

(Lythrum salicaria) is an example

of a plant that is kept in check in its native

habitat

, but is

invasive in North America. This showy wetland plant with

tall purple flowers may have arrived accidentally or been

intentionally imported to North America as a garden orna-

mental. In its native northern Europe, resident beetles feed

on its roots and leaves, keeping the loosestrife in check, so

that it only appears occasionally and temporarily in disturbed

sites. When loosestrife arrived in North America, the beetles,

along with other pests and diseases, were left behind. Loos-

estrife has proven to be extremely adaptable and has become

an aggressive weed across much of the American East and

Midwest, often taking over an entire wetland and choking

out other plants, eliminating much of the wetland

biodiv-

ersity

In addition to the competitive advantage of having

few predators, invasive exotic plants and animals may have

ecological characteristics that make them especially competi-

tive. They can be hardy, adaptable to diverse habitat condi-

tions, and able to thrive on a variety of food sources. They

may reproduce rapidly, generating large numbers of seeds

or young that spread quickly. If they are aggressive colonizers

adapted to living in marginal habitat, introduced species can

drive resident natives from their established sites and food

sources, especially around the disturbed environments of

human settlement.

This competitiveness has been a problem, for example,

with house sparrows (Passer domesticus). These birds were

intentionally introduced from Europe to North America in

1850 to control insect pests. Their aggressive foraging and

breeding habits often drive native sparrows, martins, and

bluebirds from their nests, and today they are one of the

most common birds in North America. Exotic plants can

also become nuisance species when they crowd, shade, or

out-propagate their native competitors. They can be extraor-