natural resources lands

The value of other resources is not as obvious, such as the aesthetic and recreational values of hiking trails and campgrounds in mountains, natural water filtration through aquifers, ha

Lands

Taming the Wilds

Julie Kerr Casper, Ph.d.

All rights reserved No part of this book may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage or retrieval systems, without permission in writing from the publisher For information contact: Chelsea House

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Casper, Julie Kerr.

Lands : taming the wilds / Julie Kerr Casper.

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Concepts of Land Resources

The History of Land Use

Renewable and Nonrenewable Resources

The Development of Land Resources

Multiple Uses of the Land

The Importance of Land Resources

Management of Land Resources

Conservation of Land Resources

Conclusion: Future Issues and

The Earth has been blessed with an abundant supply of natural

resources Natural resources are those elements that exist on the planet for the use and benefit of all living things Scientists commonly divide them down into distinct groups for the purposes of studying them These groups include agricultural resources, plants, animals, energy sources, landscapes, forests, minerals, and water and atmospheric resources

One thing we humans have learned is that many of the important

resources we have come to depend on are not renewable Nonrenewable

means that once a resource is depleted it is gone forever The fossil fuel that gasoline is produced from is an example of a nonrenewable resource There is only a finite supply, and once it is used up, that is the end of it

While living things such as animals are typically considered able resources, meaning they can potentially be replenished, animals hunted to extinction become nonrenewable resources As we know from past evidence, the extinctions of the dinosaurs, the woolly mam-moth, and the saber-toothed tiger were complete Sometimes, extinc-tions like this may be caused by natural factors, such as climate change,

renew-Preface

Natural Resources:

Priceless Gifts from the Earth

Mankind did not weave the web of life.

We are but one strand in it Whatever we

do to the web, we do to ourselves

All things are bound together.

—Chief Seattle

vi

drought, or flood, but many extinctions are caused by the activities of

humans

Overhunting caused the extinction of the passenger pigeon, which

was once plentiful throughout North America The bald eagle was

hunted to the brink of extinction before it became a protected species,

and African elephants are currently threatened with extinction because

they are still being hunted for their ivory tusks Overhunting is only

one potential threat, though Humans are also responsible for habitat

loss When humans change land use and convert an animal’s habitat

to a city, this destroys the animal’s living space and food sources and

promotes its endangerment

Plants can also be endangered or become extinct An important

issue facing us today is the destruction of the Earth’s tropical rain

forests Scientists believe there may be medicinal value in many plant

species that have not been discovered yet Therefore, destroying a plant

species could be destroying a medical benefit for the future

Because of human impact and influence all around the Earth, it

is important to understand our natural resources, protect them, use

them wisely, and plan for future generations The environment—land,

soil, water, plants, minerals, and animals—is a marvelously complex

and dynamic system that often changes in ways too subtle to perceive

Today, we have enlarged our vision of the landscape with which we

interact Farmers manage larger units of land, which makes their job

more complex People travel greater distances more frequently Even

when they stay at home, they experience and affect a larger share of the

world through electronic communications and economic activities—

and natural resources have made these advancements possible

The pace of change in our society has accelerated as well New

technologies are always being developed Many people no longer spend

all their time focused in one place or using things in traditional ways

People now move from one place to another and are constantly

devel-oping and using new and different resources

A sustainable society requires a sustainable environment Because

of this, we must think of natural resources in new ways Today, more

than ever, we must dedicate our efforts to conserve the land We still live

in a beautiful, largely natural world, but that world is quickly changing World population growth and our desire to live comfortably are exert-ing pressures on our soil, air, water, and other natural resources As we destroy and fragment natural habitats, we continue to push nonhuman life into ever-smaller pockets Today, we run the risk of those places becoming isolated islands on a domesticated landscape

In order to be responsible caretakers of the planet, it is important to realize that we humans have a partnership with the Earth and the other life that shares the planet with us This series presents a refreshing and

informative way to view the Earth’s natural resources Agriculture: The

Food We Grow and Animals We Raise looks at agricultural resources to

see how responsible conservation, such as caring for the soil, will give

us continued food to feed growing populations Plants: Life From the

Earth examines the multitude of plants that exist and the role they play

in biodiversity The use of plants in medicines and in other products that people use every day is also covered

In Animals: Creatures That Roam the Planet, the series focuses on

the diverse species of animals that live on the planet, including the important roles they have played in the advancement of civilization This book in the series also looks at habitat destruction, exotic species, animals that are considered in danger of extinction, and how people can help to keep the environment intact

Next, in Energy: Powering the Past, Present, and Future, the series

explores the Earth’s energy resources—such as renewable power from water, ocean energy, solar energy, wind energy, and biofuels; and non-renewable sources from oil shale, tar sands, and fossil fuels In addi-tion, the future of energy and high-tech inventions on the horizon are also explored

In Lands: Taming the Wilds, the series addresses the land and how

civilizations have been able to tame deserts, mountains, Arctic regions, forests, wetlands, and floodplains The effects that our actions can

have on the landscape for years to come are also explored In Forests:

More Than Just Trees, the series examines the Earth’s forested areas and

how unique and important these areas are to medicine, construction,

recreation, and commercial products The effects of deforestation, pest

outbreaks, and wildfires—and how these can impact people for

genera-tions to come—are also addressed

In Minerals: Gifts From the Earth, the bounty of minerals in the

Earth and the discoveries scientists have made about them are

exam-ined Moreover, this book in the series gives an overview of the critical

part minerals play in many common activities and how they affect our

lives every day

Finally, in Water and Atmosphere: The Lifeblood of Natural Systems,

the series looks at water and atmospheric resources to find out just how

these resources are the lifeblood of the natural system—from drinking

water, food production, and nutrient storage to recreational values

Drought, sea-level rise, soil management, coastal development, the

effects of air and water pollution, and deep-sea exploration and what it

holds for the future are also explored

The reader will learn the wisdom of recycling, reducing, and

reus-ing our natural resources, as well as discover many simple threus-ings that

can be done to protect the environment Practical approaches such as

not leaving the water running while brushing your teeth, turning the

lights off when leaving a room, using reusable cloth bags to transport

groceries, building a backyard wildlife refuge, planting a tree,

form-ing a carpool, or startform-ing a local neighborhood recyclform-ing program are

all explored

Everybody is somebody’s neighbor, and shared responsibility is

the key to a healthy environment The cheapest—and most effective—

conservation comes from working with nature This series presents

things that people can do for the environment now and the important

role we all can play for the future As a wise Native-American saying

goes, “We do not inherit the Earth from our ancestors—we borrow it

from our children.”

While we deal with different aspects of the land every day,

most people are not aware of just how much we depend on the land and its natural resources We depend on the land

as a source of many services—some obvious, others not so obvious Obvious uses are to grow food on, to graze our animals on, and for the necessary building materials to construct our roads and homes with Other, more subtle, values are the aesthetic characteristics enjoyed every time someone sets foot outside to enjoy nature, hike, camp, fish,

or participate in any form of outdoor recreation

I hope to instill in you—the reader—an understanding and ciation of the land and its vital role in our environment Perhaps mak-ing you more aware of the land and all that it does for each one of us every day will plant in you the seeds of conservation toward this pre-cious resource and encourage environmental awareness and the desire

appre-to protect this resource and use it wisely on a long-term basis—a

con-cept called land stewardship.

I would sincerely like to thank several of the federal government agencies that study, manage, protect, and preserve the land each day—

in particular, the Bureau of Land Management (BLM), the U.S Forest Service (USFS), the National Park Service (NPS), the U.S Department

of Agriculture (USDA), the Natural Resources Conservation Service (NRCS), and the U.S Fish and Wildlife Services (FWS) for providing

an abundance of learning resources on this important subject I would also like to acknowledge and thank the many universities across the country (and their geography, ecology, and geology departments) as well as the private organizations that diligently strive to protect our precious land resources, not only at home but worldwide

Acknowledgments

x

The lands of the Earth hold vast resources From mountains to

deserts to forests to coastlines and grasslands, each ment—or ecosystem—offers a wide range of goods and services

environ-It is difficult to assign a total dollar value to the land’s resources Some values are quantifiable, such as the value of timber in forests, the graz-ing potential in grasslands, or the food that is grown on farms The value of other resources is not as obvious, such as the aesthetic and recreational values of hiking trails and campgrounds in mountains, natural water filtration through aquifers, habitat for wildlife, carbon storage, biodiversity, soil fertility, or the land’s role in the water cycle Some of these resources are renewable; others are not—but they are all important to the environment

Each component of an ecosystem plays a part in how the entire ecosystem functions; and many components are interrelated If one land resource is mismanaged or depleted, it will often cause a ripple effect, upsetting the balance in other areas and damaging the entire system.Human impacts can have a tremendous influence on the land—both directly and indirectly Cutting down a forested area to build a housing development and a road network is a direct effect Polluting the atmo-sphere with greenhouse gases, which can pollute the environment, upset natural chemical balances such as the carbon cycle, and eventually lead

to climate change that then affects the landforms and resources in that area, would be an indirect effect When climate change causes drought,

it can destroy farmers’ ability to grow crops on the land

The Earth’s landscapes can also tell a story By understanding ous landforms, it is possible to study past climates and determine which types of natural environments existed in the geologic past Humans’ Introduction

vari-xi

influence on the land tells its own story For example, archaeologists use these concepts to study past civilizations to determine not only what their lifestyle was, but also what type of climate and vegetation existed at the time Studying the landscape can answer many historical questions concerning the influence of both natural and human factors.

Lands: Taming the Wilds addresses the important resource issues

that we face today with the landscape, as well as future management

of the land in order to preserve and protect its resources and provide responsible stewardship of the land for future generations to enjoy.Chapter 1 presents the concepts of how the Earth’s landmasses have changed over the geologic past, the effects of climate on the land, the role of ecosystems, and the resulting distribution of resources

Chapter 2 looks at the history of land use and its impact on tion and then examines more closely the evolution of land exploration and use in the United States

civiliza-Chapter 3 addresses the renewable and nonrenewable resources that are associated with rangeland, riparian corridors, wetlands, des-erts, grasslands, wilderness areas, and parks and preserves It also addresses natural resource exploration and extraction

Chapter 4 discusses the development of land resources and the role

of several natural systems, such as the rock cycle, the role of soil, the water cycle, the nitrogen cycle, the carbon cycle, and the food chain

It also looks at natural hazards and the consequences of development within those areas

Chapter 5 focuses on use of the land, such as rangeland and ing, agriculture and factory farming, the value of riparian areas, the impacts of urbanization, the use of fragile desert resources, irrigation and salinity, deforestation, pollution, and invasive species

graz-Chapter 6 illustrates the importance of land resources and the goods and services that come from them, such as food, energy, carbon storage, tourism, wildlife habitat, medicines, minerals, clean water, soil stabilization, biodiversity, recreation, scenic beauty, and open space.Chapter 7 looks at the management of natural resources and the roles and responsibilities of the various government agencies through-out the country, as well as the responsibilities of each individual It

examines resource decision-making issues and the technologies

avail-able today to enavail-able scientists and managers to be efficient stewards

of the land It examines emerging and cutting-edge management

tech-nologies involving geographic information systems (GIS), mathematical

modeling techniques, remote sensing technologies, and real-time

moni-toring tools

Chapter 8 addresses the conservation of precious land resources

It presents the concepts of land stewardship and sustainability and the

roles of designated wilderness, natural preserves and refuges, and

national parks throughout the country It also takes conservation to a

personal level and illustrates how each individual can promote

effec-tive conservation

Finally, Chapter 9 looks at future issues and sustainable resources

It focuses on the importance of reducing, recycling, and reusing;

con-trolling land degradation; new technologies and developments; and our

responsibility to work with nature to create a productive and healthy

future



ConCepTs of

Land ResouRCes

In order to understand the land and the natural resources that

land-masses have to offer, it is necessary to have an understanding of how they came to be It is important to examine the types of natural

landscapes—or biomes—that exist, the basic processes of soil

forma-tion, and practical uses of the land

Origin Of Landmasses

The continents on the Earth have not always been in the same

geo-graphical locations that they are in today At one point in geologic

time, the world was made up of a single continent, called Pangaea This

“super continent” eventually separated and drifted apart, forming the seven different continents that exist today

In 1912, Alfred Wegener, a German meteorologist, was the first scientist to propose the theory of the drifting continents He used the theory of Pangaea’s existence along with climate-related field data

Plate tectonics has been at work since the Earth was formed These tions illustrate the movement of the continents from 620 million years ago to the present

reconstruc-collected from rocks He believed that the continents are made of

lighter rocks that rest on heavier crustal material—similar to an iceberg

floating on water Wegener proposed that the positions of the

conti-nents are not rigidly fixed, but instead, move at a slow rate—roughly

one yard (one meter) per century

It was not until the 1960s, that geologists gained the technology to

understand the processes at work that could move the Earth’s plates

The concepts of seafloor spreading and plate tectonics emerged as

powerful new hypotheses to explain the features and movements of

the Earth’s surface Scientists concluded that the Earth’s surface was not

composed of one large sheet, but was composed of more than 12 major

pieces of crust These pieces of crust are called plates.

Each rigid plate, or slab, of lithosphere averages at least 50 miles

(80 kilometers) thick These plates move relative to one another at

speeds of a few inches (centimeters) per year—at roughly the same

rate as a human fingernail grows Although these velocities are slow by

human standards, they are extremely rapid by geologic ones Plates can

move 30 miles (50 km) in one million years, and the plates have already

been in motion for 100 million years Scientists recognize three

com-mon types of boundaries between the moving plates: (1) divergent, or

spreading; (2) convergent; and (3) transform, or sliding

divergent or spreading Plates

Some adjacent plates are pulling apart, such as the Mid-Atlantic

Ridge, which separates the North and South American Plates from the

Eurasian and African Plates This pulling apart causes a phenomena

called seafloor spreading as new material is added to the oceanic plates

The best-known divergent boundary is the Mid-Atlantic Ridge This

ridge is a submerged mountain range, which extends from the Arctic

Ocean to beyond the southern tip of Africa, but is just one segment of

the global mid-ocean ridge system that encircles the Earth The rate of

spread along the Mid-Atlantic Ridge averages 1 inch (2.5 cm) per year,

or 16 miles (25 km) in a million years

Convergent Plates

Plates moving in opposite directions meet and collide with each other One of the plates is dragged down, or subducted, beneath the other The

area where the plate sinks under the adjacent plate is called the subduc-­

tion zone Convergence can occur between oceanic-continental plates,

oceanic-oceanic plates, and continental-continental plates An example

of a convergent plate is the Nazca Plate (oceanic), which subducts under the South American Plate to create the majestic Andes Mountains in South America When plates push together, the Earth’s crust tends

to buckle and be pushed upward or sideways This is also how the Himalayan mountain range was formed The Himalayas, towering as high as 29,000 feet (8,854 m), form the highest continental mountains

in the world Strong, destructive earthquakes and the rapid uplift of

mountain ranges are common When an oceanic plate subducts under another oceanic plate, a trench is formed Trenches can be hundreds of miles (km) long and 5 to 7 miles (8 to 10 km) deep, cutting into the ocean floor

Transform or sliding Plates

The transform, or sliding, boundary is where one plate slides

hori-zontally past another Most transform faults are found on the ocean floor, offsetting some of the active spreading ridges and producing

zigzag plate margins Shallow earthquakes are associated with them The best-known example of a sliding plate is the San Andreas Fault Zone in California The San Andreas, which is 800 miles (1,300 km) long, slices through two-thirds of the length of California Along it, the Pacific Plate has been grinding horizontally past the North American Plate for 10 million years, at an average rate of 2 inches (5 cm) per year Land on the west side of the fault zone (Pacific Plate) is moving

in a northwesterly direction relative to the land on the east side of the fault zone (North American Plate) Because the plates are internally rigid, they interact mostly at their edges All plates move relative to each other

The fOrCe ThaT drives TeCTOniC PLaTes

The tectonic plates do not randomly drift or wander about the Earth’s

surface; definite, yet unseen forces drive them Scientists believe that

the relatively shallow forces driving lithospheric plates are also working

with forces that originate much deeper in the Earth

From seismic and other geographical evidence and laboratory

experiments, scientists generally agree with Harry Hess’s theory that

the plate-driving force is the slow movement of hot, softened mantle

Although the Earth appears to be made up of solid rock, it is actually made

up of three distinct layers: the crust, mantle, and core Each layer has its own

unique properties and chemical composition

that lies below the rigid plates Scientists also accept that the lar motion of the mantle carries the continents along, much like a conveyor belt.

circu-Below the lithospheric plates, the mantle is partially molten and can slowly flow in response to steady forces applied for long periods

of time When solid rock in the Earth’s mantle is subjected to heat and pressure in the Earth’s interior over millions of years, it can be softened and molded into different shapes

The movement within the mantle moves as a convection cell in a circular motion, similar to heating a pot of thick liquid to boiling The heated liquid rises to the surface, spreads, and begins to cool; then it sinks back to the bottom of the pot where it is reheated, rises again, and repeats the process Convection in the Earth is much slower than that

of boiling, thick liquid, however In order for convection to occur, there

This illustration shows significant plate tectonic processes and landforms, such

as mid-oceanic ridges, hot spot volcanoes, subduction zones, mountain ing, and volcano formation

build-must be a source of heat Heat within the Earth comes from two main

sources: radioactive decay and residual heat

Radioactive decay is a spontaneous process that involves the loss of

particles from the nucleus of an isotope (the parent) to form an isotope

of a new element (the daughter) Radioactive decay of naturally

occur-ring chemical elements (such as uranium, potassium, and thorium)

releases energy in the form of heat, which slowly migrates toward the

Earth’s surface Residual heat is gravitational energy left over from the

formation of the Earth 4.6 billion years ago

How and why the escape of interior heat becomes concentrated in

cer-tain regions to form convection cells is somewhat of a mystery Scientists

do believe, however, that plate subduction plays a more important role

than seafloor spreading in shaping the Earth’s surface features and

caus-ing the plates to move The gravity-controlled sinkcaus-ing of a cold, denser

oceanic slab into the subduction zone, dragging the rest of the plate along

with it, is considered to be the driving force of plate tectonics

Scientists know that forces deep within the Earth’s interior drive

plate motion However, because these powerful forces are buried so

deeply, no mechanism can be tested for directly and proved beyond a

doubt The fact that the tectonic plates have moved in the past and are

still moving today is known, but the details of why and how they move

will continue to challenge scientists in the future

Because the Earth’s plates have been in motion for millions of

years, there has been plate movement of hundreds of miles (hundreds

of km) For example, seafloor spreading over the past 100 to 200

mil-lion years has caused the Atlantic Ocean to grow from a tiny inlet of

water between the continents of Europe, Africa, and the Americas into

the vast ocean that exists today

The oceanic trenches are the deepest parts of the ocean floor

One of the most famous trenches is the Mariana Trench, located in

the Pacific Ocean just east of the Mariana Islands near Japan, where

the faster-moving Pacific Plate converges against the slower-moving

Philippine Plate The Challenger Deep, at the southern end of the

Mariana Trench, plunges deeper into the Earth’s interior—35,838 feet

(10,923 m)—than Mount Everest, the world’s tallest mountain, rises above ground The Challenger Deep is the deepest known point in the oceans, and is caused by the subducting ocean crust dragging the edge

of the continental crust down with it as it descends It gets its name

from the British survey ship Challenger II, which initially located the

deep water off the Mariana Islands in 1951 Its exact depth was covered by the Japanese in 1984, from data obtained by an instrument called a multi-beam echo sounder The pressure is tremendous at this depth—scientists believe it is 16,000 pounds per square inch

dis-Oceanic-oceanic plate convergence also results in the formation of

volcanoes Over millions of years, the erupted lava builds up on the

ocean floor until the submerged volcano rises above sea level to become

The Earth is made up of a dozen or so major plates and several minor plates Tectonic plates are constantly on the move The fastest plate races along at 6 inches (15 cm) per year while the slowest plates crawl at less than 1 inch (2.5 cm) per year Most plates are part continental and part oceanic

an island volcano Earthquakes are common along these areas, as well

The most famous example of this is the Pacific Ring of Fire—a ring of

active volcanoes ringing the Pacific basin as a result of plate tectonics.

Not all plate boundaries are as simple as the three types of

bound-aries mentioned above, however In some regions, the boundbound-aries are

not well defined because the plate movement deformation occurring

there extends over a broad belt—called a plate boundary zone These

areas typically have larger plates with several smaller fragments of

plates, called microplates, involved

raTes Of mOTiOn

Scientists can determine the rates of plate movement over geologic

time by analyzing the ocean’s floor “magnetic striping.” Small grains

of magnetite, which are found within the volcanic basalt that makes

The Pacific Ring of Fire is a zone of frequent earthquakes and volcanic

erup-tions that encircles the basin of the Pacific Ocean It is shaped like a horseshoe

and it is 24,856 miles (39,993 km) long It is associated with a nearly

con-tinuous series of oceanic trenches, island arcs, and volcanic mountain ranges

and/or plate movements It is sometimes called the circum-Pacific seismic belt

up the ocean floor, act like magnets The grains of magnetite naturally align themselves with the orientation of the Earth’s magnetic field When the magma solidifies, it effectively records the Earth’s magnetic orientation (polarity) at the time it cools Because the ocean plates are moving away from the magma source (seafloor spreading), it creates

a “stripe” of basalt with the magnetite aligned to the current “north” pole Scientists know that the Earth’s polarity reverses in intervals over time (the North becomes South and vice versa) When these polar-ity reversals occur, the magnetic striping records the flip-flops in the Earth’s magnetic field In other words, a sequence of basalt may have its grains oriented to the North followed by a sequence that has its grains oriented to the South Because scientists can calculate the approximate duration of each reversal, they can calculate the average rate of plate movement during a given time span

Evidence of past rates of plate movement can also be obtained from geologic mapping studies If a rock formation of known age is mapped on one side of a plate boundary and can be matched with the same formation on the other side of the boundary, then measuring the distance that the formation has been offset can give an estimate of the average rate of plate motion

The effeCTs Of CLimaTe On The Land

Climate is the characteristic condition of the atmosphere near the

Earth’s surface at a certain place on Earth It is the long-term weather

of that area This includes the region’s general pattern of weather conditions, seasons, and even weather extremes such as hurricanes or droughts Two of the most important factors determining an area’s climate are air temperature and precipitation

The world’s different habitats—or biomes—are controlled by

cli-mate The climate of a region will determine what vegetation will grow there, what animals will inhabit the area, and what resources naturally occur The climate system is based on the location of hot and cold air mass regions and the atmospheric circulation patterns created by the trade winds and westerlies

The trade winds north of the equator blow from the northeast

South of the equator, they blow from the southeast The trade winds of

the Northern and Southern Hemispheres meet at the equator, which

causes the air to rise As the rising air cools, clouds and rain develop

The resulting bands of cloudy and rainy weather near the equator

cre-ate the tropical conditions.

Westerlies blow from the southwest in the Northern Hemisphere

and from the northwest in the Southern Hemisphere Both the

The circulation pattern of the Earth’s atmosphere is divided into distinct zones

and has a direct influence on the climate of any particular area (Source: U.S

Geological Survey)

westerlies and trade winds blow away from the 30° latitude belt Over

large areas of this latitude, surface winds are light Air slowly descends

to replace the air that is flowing away from the region The intense heat causes all the moisture in the air to evaporate, which causes the tropical desert regions—such as the Sonoran Desert in Mexico and the Sahara in Africa

There are three basic climate groups: (1) low-latitude climates; (2) mid-latitude and subtropical climates; and (3) high-latitude cli-mates The low-latitude climates are controlled by equatorial tropical air masses In the tropical rain forest, rainfall is heavy in all months The total annual rainfall can be as much as 100 inches (250 cm) There are seasonal differences in monthly rainfall, but temperatures

The Earth can be divided up into climatic zones, based on temperature, ture, and airflow

mois-of 80°F (27°C) mostly stay constant Humidity falls between 77%

and 88% “Equal” day lengths and high cloud cover also characterize

these areas

The tropical monsoon climate has summer-onshore/winter-

offshore air movement related to the monsoonal air circulation in the

area; it has heavy, high-sun rain periods and short, low-sun drought

periods These areas include the coastal areas of southwest India,

south-western Africa, and northeast and southeast Brazil

Wet-dry tropical climates have a seasonal change that occurs

between wet tropical air masses and dry tropical air masses As a result,

there is a very wet season and a very dry season Trade winds dominate

during the dry season It gets a little cooler during this dry season but

gets hot just before the wet season

In the dry tropical desert biome, climates in the low-latitude des-­

erts are located between 18° to 28° latitude in both hemispheres These

latitude belts are centered on the Tropic of Cancer and the Tropic of

Capricorn, which lie just north and south of the equator The winds are

light, with a hot, dry heat These areas are very dry and arid and cover

12% of the Earth’s land surface

The tropical steppe climate occurs near the deserts in Australia,

Argentina, southwest Asia, Africa, and the western United States These

areas are considered semiarid, with annual rainfall distribution similar

to the nearest humid climate The largest controlling factor in these

areas is the descending, diverging circulation of subtropical highs

The climates in the mid-latitude zones are affected by two different

air masses The tropical air masses that are moving toward the poles and

the polar air masses that are moving toward the equator These two air

masses are in constant conflict Either air mass may dominate the area,

but neither has complete control The climates in this zone include humid

subtropical, dry summer subtropical (Mediterranean), humid

continen-tal, marine west coast, mid-latitude desert, and mid-latitude steppe

The humid subtropical climate has a high humidity content, with

summers like the humid tropics and winters with frost from polar

air masses Mediterranean climates are characterized by mild, moist

According to the National Aeronautics and Space Administration

(NASA), while carbon dioxide emissions, aerosols, and other factors

may impact climate, a new study offers further evidence that land surface changes may also play a significant role A study of the United States’ summer climate, using data and computer models from NASA, reported that changes in land cover, particularly vegetation, over the past 300 years have impacted regional temperatures and precipitation Studies have shown that the largest human impacts on nature have occurred since the Industrial Revolution.

NASA’s Ecosystem Computer Model was designed to trace the evolution of vegetation distribution patterns over the United States since the 1700s The computer model was a technological breakthrough that enabled scientists to study the potential impacts of land use and climate change across various regions.

NASA concluded that since 1700, land cover changes produced

a significant cooling effect of more than 1°F (−17.22°C) in parts of the Great Plains and Midwest as agriculture expanded and replaced grasslands Farmlands tend to create lower temperatures through increased evaporation.

In addition, a warming effect was found along the Atlantic Coast, where croplands have replaced forests Compared to forests, croplands are less efficient in transpiration A slight warming was also observed across the Southwest where woodlands replaced some deserts.

The study also found that land cover changes can impact local precipitation, but not as significantly as they affect temperature Researchers do say, however, that the relatively strong cooling over the central United States has probably weakened the temperature difference between land and the Gulf of Mexico, slowing the northward movement of weather systems and resulting in enhanced rainfall across Texas Air masses reaching the central lowlands regions are drier, causing reductions in rainfall NASA scientists have also determined that certain types of land cover change can decrease or increase greenhouse warming.

How Land Cover Changes Affect Summer Climate

winters and hot, dry summers Hot, humid summers and occasional

winter cold waves characterize the humid continental climates

Mild winters and mild summers characterize marine west coast

cli-mates, such as those found in coastal Oregon, Washington, and British

Columbia Mid-latitude desert climates are arid (low relative

humid-ity) and have irregular rainfall Mid-latitude steppe climates—such as

in inner Asia and the western United States—are semiarid with larger

temperature ranges and more rainfall than tropical steppe areas

The high-latitude climates have polar and Arctic air masses that

dominate these regions Canada and Siberia are two air-mass sources

that fall into this group A Southern Hemisphere counterpart to these

continental centers does not exist Air masses of Arctic origin meet polar

continental air masses along the 60th and 70th parallels of latitude

Sub-Arctic climates have brief, cool summers, and long, bitterly

cold winters They also have the largest annual temperature ranges of

any climate Tundra climate, found in Greenland, Eurasia, the Arctic

Ocean, and bordering lands of North America, is characterized as being

“summerless”—these areas experience below-freezing temperatures

at least nine months of the year Precipitation is usually less than 10

inches (25.4 cm), and these areas have low evaporation rates.

Ice cap climates are located in the interior regions of high-latitude

landmasses Covered by ice, they have a year-round influence of polar

anticyclones These areas have no summers—all months are below

freezing These areas contain the world’s coldest temperatures

Climate is a major factor in the creation of landforms that exist in

particular places on the Earth This in turn determines the resources

present at a given location and the types of land use in which humans

can engage

TyPes Of naTuraL LandsCaPes—

The WOrLd’s majOr BiOmes

Biomes are defined as the world’s major communities, classified

accord-ing to the vegetation that grows there and described by the adaptations

of living organisms to those particular environments Although there

are several ways that scientists classify biomes, the major biome types are

mountains, tundra, temperate forest, marine/island, desert, tropical dry forest, cold-climate forest, grassland, savannah, and tropical rain forest.

Biomes are not constant—they have changed and moved many times during the history of life on Earth For example, as the Earth’s plates have moved and climates have changed, an area that is desert

today may have been an aquatic or forest ecosystem millions of years

ago More recently, human activities have drastically altered ecosystem communities and landscapes For example, some forest areas that have been overcut and poorly managed have become as barren and nonfer-tile as a desert As biomes become changed or destroyed, it is critical for humans to understand the impact their actions can have on the

The major biomes of the Earth Each biome has specific plants associated with it

natural landscape Interference with the natural landscape impacts the

available resources and their quality

An ecosystem is an area on the Earth that is a community of living

organisms and their surrounding environment Every person, animal,

plant, rock, stream, and piece of land belongs to one or more

ecosys-tems For example, an ecosystem can be made up of a freshwater pond

that serves as a home for frogs, lily pads, fish, cattails, dragonflies, algae,

This illustration shows the major ecological regions of North America

mosquitoes, and protozoa Each of these organisms, along with its

sources of food, sediments, nutrients, and the water itself, is a part of

the pond ecosystem, which functions as a unit or a single community This pond could also lie deep inside a forest The pond and its inhabit-ants belong to the larger forest ecosystem, which also contains several rivers, other ponds, many kinds of wildlife, flowering plants, and trees Ecosystems on Earth are incredibly diverse, both in size and in form—a large city that contains millions of people, their homes, and a built-up landscape is an urban ecosystem, while a small wildlife preserve within that city serves as a natural ecosystem

Much like a person, an ecosystem has a given level of health A healthy ecosystem performs many valuable functions, such as flood con-trol, water purification, seed dispersal, pollination, pollutant removal, nutrient cycling, and habitat provision These functions are beneficial

to both humans and other inhabitants of ecosystems Many ecosystems experience the effects of disturbances These disturbances can be caused

by human actions, such as bulldozing a forest to build a highway, or they

can be a result of natural events, such as soil erosion from heavy rains

Humans have affected ecosystems in many different ways Any time a forest is cut down, natural lands are cultivated, towns are built, a river is dammed, a factory is built, or lands are mined, the ecosystem is altered

in some way Humans have disrupted food chains, the carbon cycle, the

nitrogen cycle, and the water cycle Disturbances often decrease the ity of an ecosystem to provide valuable functions and thereby decrease the health of the ecosystem A feature of ecosystems, from the smallest backyard to the entire globe, is that they tend to be resilient Given time, ecosystems can often recover from disturbances, maintain their health, and continue to provide the functions necessary to sustain life on Earth

abil-mountain Biome

Mountains make up one-fifth of the world’s landscapes Today, more than two billion people depend on mountain ecosystems for most of

their food, hydroelectricity, timber, and minerals About 80% of the

Earth’s freshwater originates in mountain areas

(a) A tropical island biome, Kauai, Hawaii, is a tourist destination for

thou-sands of people each year (b) Cacti are common in desert regions, such

as this desert near Phoenix, Arizona Cacti have adapted to extremely dry

conditions by having thick, waxy coverings and needles instead of leaves

(c) Mountain biomes offer recreational opportunities and scenic beauty

(d) The arctic biome hosts a multitude of glaciers, some which are several

hundred feet thick (a, b, c, photos by Nature’s Images; d, National Oceanic

and Atmospheric Administration)

c

d

All mountain biomes share a similar characteristic—rapid changes

in altitude, climate, soil, and vegetation over very short distances Because of these variabilities, mountainous areas support a wide range

of biodiversity.

Rainfall and temperature vary greatly in mountain biomes For example, lightning and thunderstorms can appear rapidly, and tempera-tures can drop from extremely hot to below freezing in just a few hours

In addition to freshwater, mountain biomes provide many resources, such as farming, logging, mining, hunting, recreation, and aesthetic resources Scientists believe the cures to many diseases may be found

in the plants in mountain biomes For example, the Himalayan yew—a slow-growing conifer—is a promising source of a drug called Taxol, which scientists believe can help cure cancer

Tundra Biome

Tundra exists in the highest northern latitudes and in the Southern Hemisphere in the Antarctic Peninsula and nearby islands This biome covers about one-fifth of the Earth’s land surface Because tempera-tures can drop to −50°F (−122°C) in the winter, it is impossible for trees to grow here Instead, the tundra landscape is dominated by low-

growing plant life and wildflowers Much of the ground is permafrost

(continually frozen) Only the top layer of the soil’s surface is able to thaw during the extremely short summer months

Despite these harsh physical conditions, many animals live in this biome Hordes of insects provide resources for feeding thousands of birds who migrate through the area to take advantage of this food source, including waterfowl and shorebirds, ravens, hawks, ptarmigans, and owls There is also a rich resource of animals in this biome, includ-ing the caribou, arctic hare, weasel, polar bear, mink, wolf, wolverine, walrus, lemming, brown bear, arctic fox, and reindeer

Temperate (deciduous) forest Biome

The temperate forest biome is found in the middle latitudes around the world, such as eastern North America, Western Europe, and eastern Asia This biome is seasonal Because the trees are deciduous (meaning

they drop their leaves in the fall), their leaves change colors as the

sea-sons go through their cycles

The temperate forest biome is one of the most altered biomes on

Earth due to human activities in this area The impact is great because

the population density of the world closely corresponds to the

distribu-tion of temperate forests Humans use the wood found in these areas

for the construction of homes and buildings and for firewood Many of

these forests have been cleared for farming and to build communities

In fact, human activity has led to the decline and loss of these forests in

many locations throughout the world

marine/island Biome

Islands can vary tremendously in characteristics, such as size, shape,

and climate Some islands are tropical and lush, providing resources

such as fruit and wood Other islands are very arid Because of islands’

variability, the island ecosystem worldwide supports a wide variety of

plant and animal life

There are two major categories of islands—continental and

oce-anic Continental islands were once part of a larger landmass and, in

recent geologic time, have become separated from the main continent

by natural forces, such as rising sea level Oceanic islands are created

from the lava of giant underwater volcanoes—such as the islands of

Hawaii Oceanic islands are usually located far from large landmasses

The natural resources found on islands are very diverse, from food,

wood, and fiber to endangered species and aesthetic values.

desert Biome

Of all the Earth’s biomes, deserts have the driest climate Many of the

world’s deserts lie between 20° to 30° north and south latitude As we

saw in the Earth’s major circulation patterns, the desert zone is where air

sinks toward the Earth’s surface and rainfall is rare because rain usually

occurs where air begins to rise, not sink Major deserts are found in North

Africa, southwestern North America, the Middle East, and Australia

Desert regions only receive a few inches (cm) of rain each year

Some deserts receive no rainfall Desert soils are often salty because

whatever little rain that does fall quickly evaporates from the ground, leaving salt and other minerals behind—minerals that can be mined as natural resources for their commercial value.

Vegetation in deserts varies widely, depending on the location In deserts, the plants are drought-tolerant and can survive for long peri-ods of time with no water Many plants adapt unique features to ensure their survival, such as thick, waxy leaves; large root systems; tap roots; and water storage capabilities

The desert animals—such as jackrabbits, owls, snakes, lizards, and tortoise—have also adjusted to extreme temperature and drought These animals are typically more active at night and around dawn and dusk, so that they avoid the scorching heat

Unfortunately, because of the careless behavior of humans, deserts are spreading over regions where there was once green, fertile land—a

process called desertification With good resource management skills,

these lands can recover over time

Tropical dry forest Biome

These forests have high temperatures throughout the entire year and

a well-defined dry season This biome occurs in areas of slightly lower rainfall that are found next to tropical rain forests The transition from tropical dry forest to tropical rain forest is not always clear-cut—the transition can change gradually over hundreds (km) of miles The dry season limits plant growth and the activity of animals These forests exist in Central America, southern Asia, and Australia

Cold-climate forest Biome

Cold-climate forests are also referred to as the taiga These cold mate forests are found at very high latitudes extending across Eurasia and North America The principal trees in these forests are coniferous (the trees carry cones) Rainfall in these areas is moderately high but is spread throughout the year, with snow covering the ground during the

cli-winter months These areas usually contain many ponds or bogs—also

called muskegs—because the sun evaporates very little water

Because of the extremely cold temperatures, the trees use a lot of

energy to grow their leaves Pine trees grow needles instead of leaves,

which is advantageous because they keep their needles all year round

Trees of this biome are also known as boreal, or as the northern

coniferous forests

Along riverbanks in these regions, willows and other trees grow

Several species of animals migrate to the taiga in the summer months.

grassland Biome

Throughout the world, grasslands are known by many different names

For example, in North America they are called a prairie; in South

Africa, they are known as a veldt; in Asia, they are a steppe; and in South

America, they are called the pampas.

This biome exists in temperate regions and is highly seasonal

Grassland areas can be huge—sometimes extending thousands of

miles (km) in North America and Asia Because grasslands are located

in temperate regions, they have hot summers that eventually dry the

grasses out and freezing winters dominated by powerful winds that

sweep over the vast open areas

The rainfall in grasslands is less than the temperate forests receive,

but more than deserts In areas where rainfall is greater, the grass can

grow very lush and thick In the spring, many grasslands support large

fields of beautiful wildflowers

Wildfires also play an important role in this ecosystem They allow

the grasslands to be open and free of shrubs and trees This is

impor-tant, because if shrubs begin to grow in grassland areas, it would not

take long for them to overrun and kill off the grass, transforming the

area into a shrubland The plants in the grasslands have adapted over

time to the wildfires and actually need them to keep healthy and grow

new vegetation in the spring

Grassland soil, usually deep, dark, and rich, is called mollisol

In drier regions, it is called aridisol Because a lot of this soil is very

rich, many of the grasslands have been converted to agriculture

Grasslands are major regions for growing crops, such as wheat and

corn Grasslands also provide a food source for bison, deer, horses, and cattle.

savannah Biome

The savannah regions are tropical grasslands, found largely in Africa,

India, and the northern regions of South America Although located in

the tropical latitudes, they are much drier than tropical forests Rainfall

averages from 20 to 60 inches (51 to 152 cm) a year and is seasonal—usually falling within a time period of a few weeks Vegetation grows after the rainfall occurs; then long periods of drought follow

The dominant plant life includes grasses and small plants Trees

also grow in the savannah, such as palm trees and thorn woodlands There are a lot of fruit trees, which provide a food source for many birds and animals

The savannah supports a wide diversity of animals Types of birds include gray louries, flycatchers, purple-crested louries, hornbills, green pigeons, and raptors Mammals in this biome include lions, leopards, cheetahs, elephants, buffaloes, giraffes, hippopotami, rhinoceroses, gazelles, zebras, kudus, and waterbucks

Tropical rain forest Biome

The tropical rain forest biome contains the richest biodiversity of all the world’s biomes—containing the most animal and plant species Unfortunately, the rain forests face the greatest threat from humans Rain forests are being destroyed at record rates—an area equivalent to

50 soccer fields disappears each minute

Rain forests offer a supply of diverse resources—such as future medicinal cures for deadly diseases Already, many drugs have been discovered that are contained within the plants of the rain forest Many scientists fear that if species are destroyed, the possible life-saving therapeutic drugs will also be lost These forests receive huge amounts

of rainfall—from 13 to 26 feet (4 to 8 m)—each year They are found mainly in Central and South America, Southeast Asia, and West Africa They occur along the equator where temperatures and humidity are

extremely high Because of the flow and moisture of the massive air

masses, it rains almost 24 hours a day In some regions, there can be

more than 15 feet (4.5 m) of rain each year Rain forests provide some

of the most diverse natural resources on Earth

The imPOrTanCe Of sOiL

Fertile soil is one of the land’s most important natural resources,

because everything that lives on land depends directly or indirectly on

soil For example, without soil, farmers could not grow plants, which

means they could not grow food for animals or people

Soil is considered a nonrenewable resource because it forms so

slowly that it can take hundreds of years for just a few inches (cm) to

form A well-developed soil that is extremely fertile could have taken

thousands of years to develop Because of this, soil resources must be

well managed If nutrients are removed, or if the soil is eroded or

over-used, vegetation will not grow well

Soil is much more than just dirt It contains particles of sand, silt,

and clay, called inorganic particles The proportion of these three types

of particles helps determine the soil type Soil that is high in sand is

easy to work with because it has a lot of open air spaces between the

sand grains This makes sand the least fertile soil because the water

drains through it quickly, carries away plant nutrients, and leaves the

soil dry Clay soils are more difficult to work with because they tend to

be sticky; however, they hold more nutrients Well-drained soils that

contain a lot of organic matter are the most fertile soils

The type of soil and what actually goes on in the soil determine

how well plants grow Five factors determine what types of soil form on

Earth: (1) parent material, (2) organisms, (3) topography, (4) climate,

and (5) time

Parent material is the primary material from which the soil is

formed Soil parent material can be bedrock; organic material;

depos-its from water, wind, glaciers, and volcanoes; or an old soil surface

Bedrock is broken down as weathering processes wear away the mineral

particles from rocks