Encyclopedia of Global Resources part 50 docx

Primary Uses Common flax is grown for both its versatile fibers and its nutritionally rich seeds.. The glossy flax seeds, either brown or golden yellow in color, con-tain high levels of

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Web Sites

Fisheries and Oceans Canada

Fisheries

http://www.dfo-mpo.gc.ca/fm-gp/index-eng.htm

U.S Fish and Wildlife Service

Fisheries and Habitat Conservation: Fisheries

Program

http://www.fws.gov/fisheries/fisheries.html

See also: Agriculture industry; Biodiversity; Coral

reefs; Coral reefs; El Niño and La Niña; Exclusive

eco-nomic zones; Fish and Wildlife Service, U.S.; Food

chain; Integrated Ocean Drilling Program; Law of the

sea; Oceans; Sea Shepherd Conservation Society

Flax

Category: Plant and animal resources

Where Found

Flax, also known as linseed, common flax, or Linum

usitatissimum in Latin, is native to the region

stretch-ing from the eastern Mediterranean to India Flax was

probably first domesticated in the Fertile Crescent

and was cultivated extensively in ancient Egypt

Primary Uses

Common flax is grown for both its versatile fibers and

its nutritionally rich seeds It is also cultivated as an

or-namental plant in gardens Various parts of the plant

have been used to produce a variety of products,

in-cluding dye, fabric, paper, linen, ropes, fish nets,

med-icines, and health foods Flax seeds contain omega-3

fatty acids, which are believed to possess anticancer

properties, to lower the risk of cardiovascular

dis-eases, and to lessen the severity of diabetes

Technical Definition

Flax is a member of the genus Linum, in the Linaceae

family It is an erect annual with slender stems and

lan-ceolate leaves The plant can grow up to 1.2 meters

tall, with leaves 2-4 centimeters long and 0.3

centime-ter wide The flower color varies, ranging from bright

red to purple or pale blue, each with five petals 1.5-2.5

centimeters in diameter When mature, each plant

produces round, dry capsules of 0.5-0.9 centimeter in

diameter, each containing several seeds The glossy

flax seeds, either brown or golden yellow in color, con-tain high levels of lignans and omega-3 fatty acids, both of which are believed to have health benefits Flax stems are wrapped around by bast fibers of high cellulosic content

Description, Distribution, and Forms

In ancient times, some flax plants were cultivated for both their fiber and their nutrient-rich seeds Modern-day flax cultivars have diverged into two sepa-rate lines, one for high seed yield and another for superior fibers The plants for seed production are more branched Seed flax is an erect annual that grows up to 91 centimeters tall and has a distinct main stem and several branches at the top that produce flowers The branched taproot system may penetrate

a depth of about 1 meter in the soil A flax flower has five petals, producing a fruit of a five-chamber cap-sule Each capsule contains an average of six to eight seeds The capsules may split open or remain tightly closed at maturity, depending upon genetic varia-tions Cultivars with tight capsules resist seed shatter-ing better than those with split capsules and thus are less likely to suffer damage from bad weather Flax is mostly a self-pollinated crop with occasional cross-pollination by some insect species The extent of cross-pollination varies with cultivars and environ-mental conditions Flax flowers typically open soon af-ter sunrise on clear days, and their petals fall within five to six hours after opening Flower color may vary from white to pink, blue, or different shades of pur-ple However, most modern-day cultivars bear blue petals Seed colors also vary from various shades of yellow, brown, greenish-yellow, and greenish-brown

to nearly black

Flax is well adapted to fertile, fine-textured clay soil at near neutral pH levels (6.0-6.5) and with a con-siderable amount of organic matter Sandy, coarse-textured peat or muck soils are not ideal for flax culti-vation Adequate moisture and cooler temperatures, especially during the reproductive phase (from flow-ering to seed maturity), are beneficial for high oil con-tent and superior oil quality The seed coat of flax can easily be damaged in harvest or during handling Even slight, often invisible damage will make seeds susceptible to decay because of their high oil and pro-tein content For this reason, seeds with no damage should be carefully selected for planting In addition, treating seeds with fungicides before planting is criti-cal to ensure a high germination rate A well-prepared

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seedbed similar to those for seeding lawn grasses is

also important for obtaining good seedling stands

The plants from which fibers are extracted are tall

annuals with few branches Since ancient times, flax

fibers have been used to make many products Ropes,

cords, tents, sails, fishing nets, and carpets can be

traced back at least three thousand years Flax fibers

are extracted from the stem and are called bast fibers

Bast fibers from flax are naturally smooth and straight,

containing small, regular lumens and regular

diame-ters with a clockwise twist Flax fibers are two to three

times stronger than cotton fibers Linen, the textile

made from flax, has long been prized for its durability

History

Flax is regarded as one of the first crops domesticated

by humans Its proposed Mediterranean origin was

supported by uncovered remains of a flax species

in ancient settlements occupied by

the Swiss Lake Dwellers about ten

thousand years ago Archaeological

evidence showed the use of flax for

both fiber and seeds by people of the

Stone Age Egyptian mummies in

an-cient tombs dated to more than five

thousand years ago were wrapped in

linen cloth made from flax fiber In

the 1990’s, excavations in eastern

Turkey found impressions of a linen

fiber carbon-dated to nine thousand

years ago In addition, carvings in

Egyptian tombs recorded flax

culti-vation along with the culticulti-vation of

figs, olives, and wheat The ancient

Greeks also used linen, while the

Ro-mans are considered responsible for

spreading the cultivation of flax

across Europe

In the United States, the early

col-onists began to cultivate flax on a

small scale, primarily for home uses

The commercial production of flax

did not begin until 1753 With the

in-vention of the cotton gin by Eli

Whit-ney in 1793, flax cultivation began to

decline and was nearly driven to

ex-tinction by the 1940’s In the latter

part of the twentieth century in

North America, flax regained some

momentum as an alternative crop

for health food Flax production for oil-rich seeds oc-curs primarily in Canada (34 percent), China (25 cent), India (9 percent), the United States (8 per-cent), and Ethiopia (3.5 perper-cent), with a combined total production of approximately 1.4 metric tons Flax cultivation for commercial textiles is in Europe (France, Belgium, the Netherlands, Spain, Russia, and Belarus), Egypt, and China

Obtaining Flax After flax is planted, the initial growth of the crop is somewhat slow, with seedlings reaching 10-15 centi-meters in six weeks Thereafter, however, the growth rate accelerates to several centimeters a day The time span from planting to harvest is about seventy to one hundred days, depending upon the climate At matu-ration, plants are cut with mowing equipment Fruit capsules are separated from the stalk, and seeds are

A worker in Germany prepares flax for use in the textile industry (AP/Wide World

Photos)

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released by gentle threshing Oil is pressed from

flax-seeds and further extracted using a petroleum

sol-vent

Strands of fiber are attached longitudinally to the

stem, between the epidermis and the central woody

core The flax fiber, with a very high cellulose

concen-tration, is extracted by retting and scutching Retting

begins with submerging the flax stems in water and

ends with rotting away the inner stalk, leaving the

outer fibers intact Following retting, the stalk is

sun-or wind-dried and then broken into shsun-ort bits, leaving

the fiber unharmed The scutching scrapes the straw

away from the fiber and combs non-fiber residue out

of the fiber

Uses of Flax

Flaxseed (linseed) is produced primarily for the value

of its oil Linseed oil is one of the oldest commercial

oils used by humans Flax has been cultivated as a

com-mercial oilseed crop in the United States and Canada

for more than one century In general, however,

sol-vent-processed oil from brown flax has been used for

many centuries in paints and varnishes, although it

has not been usable for food or feed The linseed

meal, a by-product after oil extraction, however, is

of-ten used in animal feed and organic fertilizers

Use of flaxseed as a food has increased in recent

years because of its beneficial health effects from

three major components: a high omega-3 fatty acid

content, high dietary fiber, and the highest lignan

content of all plants Although color variations can

range from golden yellow to brown, seeds have similar

nutritional values and equal amounts of omega-3 fatty

acids Omega-3 fatty acid, similar to that which is

found in fish like salmon, acts to lower total

choles-terol and low-density lipoprotein (LDL) levels,

im-prove cardiovascular health, and promote skin health

The high fiber content also helps lower cholesterol

and reduce colon and stomach cancers Lignan acts as

both a phytoestrogen and an antioxidant, which

re-duces the risk of various cancers In addition, a very

low amount of carbohydrates makes flaxseed ideal for

diabetes and weight loss and maintenance These

potential health benefits have resulted in a steady

in-crease in consumption of whole seeds, ground seeds,

and linseed oil

Flax stem fiber is soft, lustrous, and flexible; it is stronger than cotton fiber but less elastic The top quality flax fibers are used for linen fabrics Lower grades are used for the manufacturing of twine and ropes Other products made from flax fibers include cigarette paper, paper for banknotes, reinforcing ma-terials in plastics, erosion control mats, and interior panels and mats in automobiles A growing demand for natural fibers exists in Europe Fibers extracted from flax, hemp, and jute are blended with synthetic fibers to make automotive head liners and other in-terior components A composite material composed

of flax fiber and polypropylene combines excellent strength and durability with moisture resistance, which

is suitable for use in carpet backings, filters, insula-tion, geotextiles for erosion control, and upholstery padding

Ming Y Zheng

Further Reading

Beutler, Jade Flax for Life! 101 Delicious Recipes and Tips Featuring Fabulous Flax Oil Vancouver: Apple,

1996

Foulk, J A., et al “Flax Fiber: Potential for a New Crop

in the Southeast.” In Trends in New Crops and New Uses, edited by Jules Janick and Anna Whipkey

Al-exandria, Va.: ASHS Press, 2002

Joiner-Bey, Herb The Healing Power of Flax Topanga,

Calif.: Freedom Press, 2004

Moquette-Magee, Elaine The Flax Cookbook: Recipes and Strategies for Getting the Most from the Most Power-ful Plants on the Planet New York: Marlowe, 2004 Reinhardt-Martin, Jane Flax Your Way to Better Health.

Silvis, Ill.: Author, 2001

Web Site Flax-Seed.org Flax Seed Oil http://www.flax-seed.org/

See also: Cotton; Deforestation; Forestry; Global Strategy for Plant Conservation; Hemp; Paper, alter-native sources of; Plant fibers; Plants as a medical re-source; Renewable and nonrenewable resources; Textiles and fabrics; Wheat

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Floods and flood control

Categories: Environment, conservation, and

resource management; geological processes and

formations

Floods can have both devastating and positive effects

on natural resources and human infrastructure.

Background

Floods happen with any high flow of surface waters

that overtop normal confining banks and cover land

that is usually dry Floods occur naturally along most

river systems Low-lying areas and areas downstream

of dams are most at risk Flooding causes loss of

hu-man and animal life; structural damage to bridges,

buildings, roadbeds, and utilities; soil erosion;

de-struction of property; and dede-struction of livestock

and crops that provide food for people As a result,

famines may follow floods, with large numbers of

peo-ple dying from starvation Floodwaters are typically

contaminated with raw sewage, including both

hu-man and animal waste, and may contain dangerous levels of bacteria, leading to outbreaks of waterborne illness

Floods also can have positive impacts Floods re-charge natural ecosystems; provide abundant fresh water for agriculture, health, and sanitation; and de-posit nutrient-rich sediment on floodplains, enhanc-ing crop yields The importance of floods to aquatic ecosystems is demonstrated by the artificial flooding

in the Grand Canyon of the Colorado River in the United States

However, floods are the most devastating of all geo-logical agents, surpassing earthquakes and volcanic eruptions in terms of loss of life and property damage

In developing countries, floods cause a large number

of deaths, whereas in developed countries, floods cause billions of dollars worth of property damage Each year there are between fifty and three hundred inland floods worldwide, impacting an estimated 520 million people and causing as many as 25,000 deaths Since 1985, inland floods have killed approximately 130,000 people (not including loss of life from storm

Survivors of a deadly flood in Ecuador struggle to salvage their belongings in knee-deep waters (Xinhua/Landov)

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surge and tsunami-related floods) Floods and other

water-related disasters cost the world economy as

much as $50 to $60 billion per year Globally, the

greatest potential for flooding exists in Asia, where

more than 1,200 floods occurred between 1900 and

2006, claiming an average of 5,300 lives and costing

up to $207 billion in losses As urbanization increases,

particularly in flood-prone areas, the potential for

flooding rises because of land-use changes (such as

deforestation and the covering of once-permeable

ground with concrete, asphalt, and buildings)

Cli-mate change and sea-level rise also lead to increased

flooding Nearly 1 billion people, about one-sixth of

the world’s population, live in areas prone to

flood-ing Many of these people are among the world’s

poorest inhabitants, depending on fertile floodplain

soils and wetlands for agriculture and economic

op-portunity

Floodplains

Most streams are naturally bordered by flat, low-lying

areas known as floodplains Floodplains have been

carved into the landscape by stream erosion and are

covered in fine-grained sand, silt, and clay deposited

by floodwaters Some streams have natural levees,

moundlike deposits of sediment that border the

stream channel Natural levees form as floodwaters

leave the channel and spread onto the floodplain As

rushing water leaves the channel, its velocity drops,

and coarser sediment is deposited adjacent to the

stream Man-made levees may be built along streams

in an attempt to control flooding However, if the

water in a stream is allowed to spread over its natural

floodplain, the impact of downstream flooding is

less-ened

Types of Floods

Floods occur when a drainage basin (or watershed)

receives so much water that stream and river channels

cannot handle the flow After a rain, some water

infil-trates the soil, some evaporates or is used by plants,

and the remainder (about 30 percent) becomes

run-off, flowing across the ground surface

Riverine floods occur when heavy rainfall or spring

thaws (melting snow and ice) increase water levels in a

drainage basin Heavy rainfall may be the result of a

hurricane, a tropical cyclone, a monsoonal rain, or a

prolonged period of unusually wet weather, as in the

case of the Great Midwest Flood of 1993 in the central

United States, which impacted nine states along the

Mississippi River and lasted more than four months

In cold climate areas where rivers freeze in the win-ter, spring thaws bring ice jams and associated flood-ing Rising water levels lift river ice, which breaks into large sheets that float downstream and pile up near narrow passages or against obstructions such as bridges When the ice stops moving because of a jam, floodwaters rapidly spread over the riverbanks up-stream from the jam and may cover vast areas of usu-ally dry land, flooding roads and causing property damage When the ice jam breaks, a sudden flood of water is released Ice jam flooding occurs in Canada, the northern United States, Europe, Russia, Kazakh-stan, China, and other countries

Flash floods are associated with intense storms that release large amounts of rain into small drainage bas-ins in a relatively short period of time Flash floods oc-cur with little or no warning and can reach peak levels within minutes, carrying a deadly cargo of rocks, trees, and other debris Fifteen centimeters of swiftly moving water can sweep people off their feet, and cars can be swept away by 0.6 meter of water A notable flash flood occurred July 31, 1976, along the Big Thompson River near Denver, Colorado, after an un-usually heavy rainstorm A wall of water 5.8 meters high roared down a canyon where people were camp-ing The flood killed 140 people and caused millions

of dollars in property damage Flash floods may even occur in dry streambeds on sunny days when small but heavy rainstorms occur upstream kilometers away Storm surge floods (coastal floods) occur when on-shore winds and hurricanes cause the sea level to rise over low-lying coastal areas If storm surges happen during high tide, leading to a tidal surge, the devasta-tion can be catastrophic Sometimes during hurri-canes coastal areas are affected simultaneously by storm surges and riverine floods In May, 2008, Cy-clone Nargis struck Myanmar (Burma) with storm surge, flooding up to 4 meters in the densely popu-lated Irrawaddy Delta region The death toll was esti-mated to be more than 100,000

Coastal flooding can also occur as a result of a tsu-nami or seismic sea wave following an earthquake On December 26, 2004, a magnitude 9.3 earthquake off the coast of the Indonesian island of Sumatra pro-duced a tsunami in the Indian Ocean that flooded coastal areas across Southeast Asia, Sri Lanka, India, and other nations bordering the Indian Ocean, in-cluding Australia and several African countries The tsunami, which was up to 25 meters high, killed nearly

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300,000 people and left more than 1.5 million

home-less Billions of dollars worth of property damage

occurred, and several islands were completely

sub-merged

Floods can also be caused by human interference

with a drainage basin The most obvious example is

the bursting of dams or levees Dam failures represent

potentially the worst flooding event in terms of

sud-den, catastrophic loss of life and destruction of

prop-erty Dam failures are primarily caused by neglect,

poor design, or structural damage caused by an

earth-quake or other event The deadliest flood in U.S

his-tory was the result of a dam failure on the Little

Conemaugh River in Johnstown, Pennsylvania, on

May 31, 1889 A wall of water 12 meters high killed

2,200 people

Notable Floods

Near the end of the last ice age, about thirteen

thou-sand years ago, glacial-related ice jam flooding in the

northwestern United States formed prehistoric Lake

Missoula along the Clark Fork River in Montana

When the ice jam broke up, the water in the lake,

which was about 600 meters deep with a volume of

about 2,500 cubic kilometers, was released

cata-strophically, flowing westward and both creating the

Channeled Scablands and eroding immense

chan-nels across the Columbia Plateau

The worst natural disasters in history, in terms of

loss of life, have been floods along Chinese rivers The

Huang River (also known as the Yellow River) in

China has killed more people than any other natural

feature Over the past three to four thousand years, it

has flooded 1,593 times The river’s English name

de-rives from the ochre-yellow color of the silt carried by

the river Millions of metric tons of silt deposited on

the riverbed choke the channel and displace the

water, and, over time, the river level rises To prevent

flooding and to keep the river within its banks, the

Chinese built levees or earthen embankments along

the sides of the river As the sediment accumulated in

the river channel, the levees had to be built higher

and higher In places, the riverbed is higher than the

surrounding countryside, with levees towering 9

me-ters or more above the floodplain In 1887, heavy

rains over a period of months caused the river level to

rise The levees broke catastrophically, spilling

flood-waters 3 meters deep over the surrounding

country-side and covering an estimated 129,500 square

kilo-meters The flooding claimed between 900,000 and 6

million lives (estimates vary widely; the larger figure includes deaths from flood-induced famine) A flood

on the same river in 1931 killed nearly 4 million peo-ple The longest river in China, the Chang (also known as the Yangtze), has also flooded numerous times In 1911, a flood on the Chang River claimed 100,000 lives In 1931, the river crested at nearly 31 meters above its normal level and killed 145,000, but

as many as 3,700,000 died as a result of starvation be-cause the flooded area normally produced nearly one-half of China’s grain Other more recent floods

on the Chang occurred in 1954, killing 30,000, and

in 1998 In an effort to control flooding along the Chang, as well as to generate electricity, the Three Gorges Dam was completed in 2006

Hurricane Katrina, which struck the southeast-ern United States in August, 2005, caused flooding along the coast of the Gulf of Mexico from Florida to Texas Federal disaster declarations covered an area

of 233,000 square kilometers Much of the damage was caused by the highest storm surge in U.S history (8.2 meters) as the hurricane approached the Missis-sippi coast However, the most severe damage was in New Orleans, Louisiana, where the man-made levees and floodwalls along the Mississippi River failed in more than fifty places, flooding 80 percent of the city Floodwaters covered the area for weeks, and at least 1,836 people were killed and 705 were missing This was the costliest natural disaster in U.S history, with damage estimates near $100 billion

Human Influences on Flooding Human activities along waterways can increase flood-ing inadvertently Pavflood-ing and buildflood-ing on floodplains and surrounding areas decrease infiltration of rainwa-ter into the soil and, as a consequence, increase run-off Runoff also increases when forests are cleared

or when wetlands are destroyed by construction or infilling Agriculture decreases the ability of soil to re-tain water and therefore increases runoff Rapid run-off causes soil erosion Sediment-clogged streams can-not support normal levels of aquatic life, and wildlife habitats are destroyed Sediment deposition in stream channels also leaves little room for water and leads to the likelihood of flooding

Effects of Flooding People are attracted to floodplains because floods de-posit nutrient-rich topsoil, eroded from upstream, pro-ducing fertile land for agriculture In Egypt, for

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ple, floods and deposition of nutrient-rich sediment

from the Nile River have increased agricultural yields

for perhaps five thousand years Floodplains tend to

be flat, making them easy to cultivate, and near water,

making them easy to irrigate In addition, the nearby

source of water is useful for transportation of

agricul-tural products Flooding is beneficial to streams as well:

It serves to maintain both local and regional

environ-mental balance, affecting water quality and aquatic

life Floods also recharge groundwater supplies

Floods can be considered human-caused disasters

in that people build on floodplains, refusing to

con-sider the risk Dangers of flooding include losses of

both human and animal lives; structural damage to

bridges, buildings, roadbeds, dams, and utilities;

ag-ricultural losses; severe soil erosion (sometimes even

unearthing coffins in cemeteries and washing them

downstream); and property destruction Most flood

deaths are attributable to drowning, and in the

United States, more than one-half of them are

associ-ated with motor vehicles being driven into areas

cov-ered by water

When water filtration facilities are inundated, floods spread waters polluted by industrial contami-nants and human waste Polluted floodwater can also contaminate wells and water supplies Wild animals, including poisonous snakes, often come into homes with rising floodwater Disease spread by waterborne pathogens and insects such as mosquitoes, in addition

to famine due to crop damage and loss of food sup-plies, can cause great loss of life Additional long-term problems include homelessness and losses to com-merce, employment, and education

Flood Control Floods can be controlled in two ways: by controlling the waters or by controlling floodplain development

To minimize the effects of flooding, engineers build dams, levees, and floodwalls along rivers Dams can store water during periods of heavy runoff and release

it gradually during periods of low flow Artificial levees and floodwalls are built along streams to confine floodwaters and to keep them from covering the floodplain As more communities build levees,

Father and son paddle through flooded streets after heavy rains in Poquoson, Virginia, in 2009 (AP/Wide World Photos)

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ever, river levels rise because floodwaters cannot

spread out The river deposits its sediment in the

channel instead of on the floodplain, raising the

riverbed and displacing the water Artificial levees

must be heightened because of rising water levels over

time

Levees are by no means a foolproof solution to

flood prevention Floodwaters occasionally overflow

levees, burst through them, or go around their

up-stream ends Where levees or floodwalls are built on

only one side of a river, towns on the other side

experi-ence higher flood levels than normal Other methods

of flood control include restoring vegetation,

institut-ing soil conservation measures, constructinstitut-ing

flood-ways to divert floodwaters, widening rivers to

accom-modate more water, and purposely flooding certain

areas to prevent flooding in others

Flood Frequency

Flood frequencies are described in statistical terms

to estimate the chance of a particular flood level For

example, the term “one-hundred-year flood” means

that a flood of a particular level will have a 1 percent

chance of occurring within a given year It does not

mean that a flood of this level would happen only

once in one hundred years A one-hundred-year flood

can occur any time Similarly, a “ten-year flood” has a

10 percent chance of occurring in a given year In

some cases, the difference between a ten-year and a

one-hundred-year flood is only a few centimeters

Around the world, the number of catastrophic

in-land floods was twice as large per decade between

1996 and 2005 as it was between 1950 and 1980

Prop-erty damage was five times as large The increase is

pri-marily attributed to socioeconomic reasons such as

population growth and changes in land use,

includ-ing increased buildinclud-ing on floodplains

Floods and Global Warming

With global climate change and predictions about

in-creases in temperature, the potential exists for the

hydrologic cycle to intensify, leading to more

ex-tremes in climate For every 1° Celsius in temperature

rise, the capacity of the atmosphere to hold water

in-creases by 7 percent This creates the potential for

more intense precipitation and, as a consequence,

more intense flooding In recent years, changes also

have occurred in the timing of floods, including a

de-crease in the number of ice-jam floods in Europe

During the twentieth century, sea level rose 10-20

centimeters Sea level is expected to rise 9-88 centime-ters by the end of the twenty-first century, suggesting that coastal flooding will become more widespread This will have a significant impact on coastal inhabi-tants; more than 70 percent of the world’s population lives on coastal plains Increasingly, islands are af-fected by sea-level rise The Pacific island nation of Kiribati, which has already lost two islands to rising seas, is a prime example In early 2005, several other islands in Kiribati were flooded by high spring tides that damaged buildings, contaminated wells with salt water, and eroded farmland A sea-level rise of 1 meter would have a devastating effect on some of the world’s poorest countries, displacing tens of millions of peo-ple and flooding low-lying areas used for growing rice and other food crops

Pamela J W Gore

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