bbc planet earth

8/3/2019 BBC Planet Earth

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To be make an review

1. Rainforest2. Tundra3. Desert4.

Saltwater5. Freshwater

Mountain's Majesty

One-fifth of the Earth's land surface is mountains. But only one in 10 people live in these ruggedand beautiful places.

Until just a few decades ago, the secrets of making mountains were largely a mystery. Geologistscould make sense of how volcanoes build themselves higher with their own lava, but how do

ocean sediments end up on top of the Andes of South America?

It was the theory of plate tectonics accepted by geologists in the 1960s that finallyprovided some sensible answers. Simply put, where the rafts, or plates, of Earth's brittle crustcollide, that's where most mountains tend to be. It's also where most of the earthquakes,volcanoes and other geological violence tend to gang up and make a ruckus.

The Himalayan Range, for instance, is growing every day as the Indian Plate continues to smashnorth into the much larger Asian Plate. The rumpled, contorted rocks of the collision form thehighest mountain range on the planet. Among those rocks are old ocean sediments right up atthe very summit of Mount Everest. Just like in the Andes.

What Goes Up ...But as sure as they rise, rain, ice and snow are tearing mountains down. That's the irony of beinga mountain on planet Earth: the higher a mountain reaches, the more clouds gather round itsheights, dumping rain and snow on it to erode it away. The Appalachians were once a toweringmountain range. But because the tectonic collision that pushed them up ended long ago, the oldrange is slowly melting away.

The Himalayas are putting up a better fight. The Indian monsoons wear them down, but theongoing collision of plates keeps pushing the mountains up as well and so a balance has beenstruck.

The flip side to all this mountain weather is that it feeds glaciers and fills rivers with just aboutall the freshwater on the planet. By forcing air to rise into chillier altitudes, mountains forcewater vapor to condense and deposit rain or snow on the land. All that water eventually feeds therivers, lakes and streams that sustain our crops and provide water to cities and industries.


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Mountains also come down more violently. Avalanches are an extreme danger in somemountainous regions. The worst are in places where old layers of rock are tilted downslope andthen lubricated with water.

Volcanoes can also blow themselves apart in an instant as was seen when Mount St. Helens

literally lost its top in 1980.

Penetrating Deep Oceans

The deep sea seems almost to belong to another planet. Bizarre, little understood creatures livethere in perpetual darkness and under mountainous pressures vampire squids, sawtooth eels,sea spiders. They and many others have largely eluded science or appear for a tantalizing

moment before the headlamps of submersibles only to vanish again.

Despite decades of exploration, less than a tenth of the deep ocean realm has been explored,despite it being the largest habitat for life on Earth. There are a lot of sea monsters yet to bediscovered.

The deep sea is invisible to anyone on a ship, of course. It's just the open ocean. But there aresubtle signs even on the surface that great depths lie below. Creatures like great whales,albatrosses, tuna and sharks may be seen. But no sea gulls, harbor seals or otters are found inthese expanses. To live in this part of the ocean, an animal has to swim all the time. There is noplace to rest or hide from natural enemies.

The AbyssTechnically speaking, the deep sea is any place away from coasts and beyond the continentalshelves where the seafloor drops away to extreme depths miles deep. These vast regions wereonce considered lifeless or perhaps inhabited by monstrous squids and little else.

Explorers using remotely operated submersible vehicles have begun to penetrate these darkdepths, and they have discovered bizarre gardens rife with life around smoking hydrothermalvents. The gardens host entire communities of life that never see the sun and have no need of it.Giant tube worms, clams and shrimp live all around these "black smoker" vents, surviving offthe exotic primitive "archaea," bacteria-like organisms that extract a living from the chemicals

dissolved in the hot mineral-rich waters spewing from the seafloor.The minerals that come out of the smoker vents are not only of interest to sea life. Humans arepreparing to mine the thick crusts created by the vents for their gold, silver and copper. Somegeologists suspect that all the major copper deposits now found on land are actually thefossilized remains of deep sea smoker vents. Already mineral rights have been granted to acompany to look for metal-rich lodes over 1,500 square miles (4,000 square kilometers) of the


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Bismarck Sea, north of New Guinea, according to a report by the American Association for theAdvancement of Science.

But even far from these extraordinary gardens, also under more than 10,000 feet of water, themuddy expanses of the seafloor can still harbor animals like sea urchins and shrimp that live

off the debris that slowly descends from the more productive waters high above. There have evenbeen discoveries of deep-sea corals growing on ledges of rock 650 to 5,000 feet deep off theAtlantic coast of Canada in cold waters a far cry from what most people think of when theyhear the words "coral reef."

Poison ZonesUnfortunately, the old idea that the deep sea is lifeless has led to a long history of dumping someof the most toxic waste into the seas. Though now illegal, not long ago everything from sewagesludge to drums of radioactive waste were dumped into the deep sea. Hydrocarbons from oceandrilling operations are still a source of deep-sea pollution.

According to the United Nations Environment Program (UNEP), dumping accounts for about 10percent of all pollution to the deep sea. The top source of pollution is runoff from land (44percent), followed by air pollution (33 percent) and losses from shipping (12 percent). Offshoreoil and gas exploration and production adds about 1 percent more of toxic chemicals usuallyconcentrated in areas like the Gulf of Mexico and the North Sea, where they cause a far greaterproportion of the deep-sea pollution.

Global StorehouseThe deep sea also plays another role often overlooked in the operation of Earth: storing heat.Seawater that is warmed at the surface eventually becomes dense with salts and sinks into thedeep sea. There it retains heat that can take centuries to come again to the surface. This is a

critical concern regarding global warming, since the only way to truly cool down Earth is toexpel the heat trapped by the greenhouse effect into space. That's harder to do when the heat istrapped in the deep sea and taking its time coming up again.

Finally, there's the matter of carbon dioxide, the most notorious greenhouse gas. Microscopicocean plants account for about half of all the carbon dioxide-absorbing photosynthesis on theplanet. A lot of the carbon trapped by sea life near the surface eventually drops to the seafloorand is buried there sequestered away from the atmosphere and out of the global warmingequation for a long time. Without this giant carbon dioxide sink, the gas would increase faster inthe atmosphere and global warming would accelerate even more quickly than it already is.

So no matter how otherworldly the deep sea may seem, it is actually an essential part of lifeeverywhere on planet Earth.


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Deserted Land

Upon hearing the word "desert" most people conjure up images of lots of sand and heat. It's acommon misconception. Some deserts are blazing hot and others happen to be the coldest, least

sandy places on Earth, like Antarctica, for instance, or the frigid Gobi Desert of China.

About the only thing all deserts have in common is their lack of abundant and reliable water.They are dry. That, as the word implies, makes them some of the most open, treeless, desertedlands in the world. And because they are already living on the edge, the habitats of desertanimals and plants also tend to be among the most easily disrupted, according to desertresearchers.

Desert RecipeIn the simplest terms, a desert can be defined as anyplace where the rain- or snowfall is less thanthe rate that things dry up. As to why they exist at all, one need look no further than a satellite

image of Earth, or a world map with all the major deserts highlighted, to see that there's amethod to the planet's deserts: The majority of desert lands fall inside two bands north and southof the tropics, at midlatitudes.

The reason for this is atmospheric. It starts in the tropics where there the sun beats downferociously and evaporates a lot of water, causing the thunderheads to pile up. As that warmedair reaches higher altitudes, it cools and rains out its moisture, then is pushed toward the poles byglobal air currents. This dried-out air tends to cycle back down over the midlatitudes where itcreates high-pressure systems. High-pressure systems result in fair, dry weather, as anymeteorologist can attest, whereas low-pressure systems spawn storms.

Another thing that grows deserts is the rain shadow effect, which is created by mountainsblocking wet weather from inland areas. When a storm has to climb a mountain, its air cools withthe higher altitude and produces more rain and snow dumping the moisture on the mountains.By the time the air makes it to the desert, it's squeezed dry.

Some desert areas have multiple mountain ranges blocking moisture, like Death Valley, inCalifornia, which is cut off from Pacific Ocean storms by no less than three mountain ranges.


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Other deserts are behind only one range, but they are real doozies: the Atacama of Peru, which isbehind the Andes, and the Tibetan Plateau and Gobi, which are behind the gigantic Himalayas.

A third ingredient for a desert is cool water offshore if an ocean is nearby, that is. Coldcurrents, like those off the western United States, western and southern Australia, or

southwestern Africa, don't tend to spawn summer rainstorms, and they keep coastal and interiorareas dry. It's the opposite case along the Atlantic Coast of the U.S., which has very warm watersfrom the Gulf Stream. The warm, moist air makes for muggy summers and wetter winters aswell.

WastelandsFinally, humans have long played a role in making deserts, but not the kind that are particularlygood for wildlife or people. Many human activities can degrade marginal lands, i.e., those thatare nearly deserts, and drive them over the edge.

"Good examples include land degradation as a result of vegetation loss due to grazing and/or

drought," says Nicholas Lancaster, researcher and director of the Center for Arid LandsEnvironmental Management at the Desert Research Institute in Reno, Nev. His list of mostdesert-degrading human activities is topped by surface disturbance by off-road vehicles andanimals, increasing salinity of agricultural lands due to poor irrigation practices, scarce waterresources, and overuse of surface water and groundwater, and urbanization of growingpopulations.

Overgrazing of animals and poor agricultural practices, both of which cause massive soil lossand erosion, takes about 12 million hectares of marginal lands out of use every year, according toan online report by the American Association for the Advancement of Science (AAAS).

This is not only bad for desert wildlife, but it's a human tragedy. Some examples: Since 1965,degradation of already marginal lands on the edge of the Sahara Desert forced one-sixth of thepeople of Burkina Faso and Mali to flee to cities. Between 1965 and 1988, in Mauritania, theproportion of nomads who grazed animals on the land fell from 73 percent to 7 percent, while thepopulation of the capital city Nouakchott shot up from 9 percent to 41 percent, according toAAAS.

Global warming is also making itself known in the American deserts. The mysterious die-off ofvast stands of pion trees the source of pine nuts valued by humans and wildlife may befrom hotter summers in the higher elevation deserts of Arizona and New Mexico.

The warming climate is also tinkering with where, when and how much rain falls in deserts,although the specifics are still unclear. Some desert regions may get greener. Others mayexperience droughts that last for decades potentially drying up entire cities.

Good NewsBut there is good news. Some marginal lands that were thought to be on the verge have beenbrought back from the brink. One example is the Machakos District in Kenya. In the 1930s, it


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was thought to be a lost cause. But over the decades, despite a population explosion, water andsoil conservation measures have improved the land.

These measures include cutting hillside terraces to stop soil erosion and digging water-storageponds, according to work by Mary Tiffin of Drylands Research in the United Kingdom. New

farming methods have also helped in densely populated, semi-arid areas of northern Nigeria,according to Tiffin and her colleagues.

So, even though many deserts are becoming a lot less deserted, there's no reason they have tobecome wastelands as well.

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orlds From Top to BottomThe expression the ends of the Earth is never better applied than to the poles. They are truly theleast hospitable regions on the surface of the planet beating out some pretty hot, arid or justsimply starved and deserted places. Some parts of Earth's polar regions are so frigid and harsh, infact, they resemble Mars more than Earth, which is why some Mars enthusiasts spend time there,practicing for a manned mission to the real Red Planet.

The deep chill is, of course, largely why the poles are the least populated regions of Earth. Thereare no permanent human residents of Antarctica, and about 3.7 million Arctic residents arespread out over eight countries. That's about the same population as Connecticut, Ireland or

Lithuania. Not a lot as populations go by today's standards.Geometry of FrigidThe frozen poles are no accident, of course. They are a product of our spherical planet. The coldis the fault of geometry: The sun is low in the sky at high latitudes, which means that even atnoontime shadows are still long and sunlight is spread thinly over a lot of ground. In starkcontrast, at the equator a person casts a shadow on little more than their own feet. Sunlightstrikes the ground at the equator perpendicularly delivering a lot of energy to a small patch ofground.

The low angle of the polar sun, combined with the tilt in Earth's spin axis, also give polar regionsthe greatest range of daylight hours through the year. At one extreme is midsummer when thesun never sets; at the other are midwinter nights when the sun never rises. Again, that's the exactopposite of the equator, where the sun is always high in the sky and days are all virtually thesame: 12 hours of light and 12 hours of dark.

These extremes make for some very different creatures. It is eternal spring in the tropics. Seasonsthere revolve around wet and dry, not cold and hot. The excess of energy in the tropics createslayer upon layer of life, forests with multiple canopies and birds with spectacular plumage.


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Meanwhile, winter never really leaves the poles. It's always either cold or very cold. To live heremeans either sleeping most of the year or piling on the blubber. There isn't a lot of time or energyto spare for bright colors or elaborate displays. Seals, penguins, polar bears, Arctic whales andtundra plants aren't particularly flashy. That's not what it takes to survive at the top and bottom ofthe world.

Melt MysteryDespite a large and growing interest in polar regions by scientists and the public, they areremarkably mysterious and difficult places to study.

Take the Arctic sea ice, for instance. It's been in the news a lot lately because over the years it'sbeen covering less and less of the Arctic Ocean in summertime. The sea ice is shrinking andgetting thinner as well. The latest study from the National Center for Atmospheric Researchestimates that the Arctic Sea will have ice-free summers by the year 2040 because of globalwarming.

But the exact mechanism causing the melting of the ice is still up for grabs. Some researchersthink it's warmer water moving up through the Bering Strait and melting the ice from below.Other scientists suspect a combination of air temperature and a vicious cycle of dark, openwaters absorbing more solar energy than ice, and therefore perpetuating more open water. Eitherway, the situation is expected to accelerate as the ever thinner ice simply crumbles.

Megadune Mega-MysteryAnother mystery that's a lot less worrisome but nonetheless puzzling is the megadunes ofAntarctica. Unlike dunes made from snow, the Antarctic megadunes are broad, undulating wavesin the surface of an ice sheet. The dunes are 6.5 to 13 feet (2 to 4 meters) high and one to threemiles (two to five kilometers) apart. They were first spotted by pilots, but satellite images

revealed vast areas covered by the dunes some as large as the entire state of California. Thefeatures are too large to be seen from the ground.

Scientists have tried to explain the dunes in various ways including some strange atmosphericprocesses that sound more like they belong on Mars or Pluto than Earth. But since they are prettyhard to visit and even harder to see being made, no explanation has taken hold.

Climatic CanaryWhat polar researchers can say for certain is that the polar regions are feeling global warmingmore acutely than the rest of the world. Polar animals and plants that have evolved to live on iceor permafrost already feel the heat because their lifestyles depend on one critical number: 32degrees F (0 degrees C). Above that number their way of life is threatened or nonexistent. As theglobal climate heats up, there will be fewer and fewer places for cold-region creatures to hide.


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Sheltering Shallow Seas

It's the ocean next door, i.e., the shallow seas that the vast majority of ocean life calls home.Shallow seas are rich with coral reefs, mangrove swamps, kelp forests and sea-grass plains, andinclude open waters off icy islands, thick with penguins, krill and whales.

The shallow ocean realms are the rain forests of the sea vital to capturing carbon dioxide fromthe atmosphere and expelling oxygen. They are also where we get the vast majority of ourseafood and, paradoxically, the part of the oceans that get the most polluted runoff from humanactivities on land. These waters are also where whales come to give birth and suckle their young.Whether it's humpbacks off the Hawaiian Islands or gray whales off the coast of Baja California,shallow bays and the waters near islands provide shelter for some of the most impressive marinemammals found anywhere on the planet.

Lights, Nutrients ... Action!What makes shallow seas explosively alive is that they are at the intersection of two worlds:outer space and the deep ocean. Outer space starts right above sea level, at least from a fish'spoint of view. It's where the light from the sun is strongest and able to illuminate the upper 100feet or so of water.

The deep ocean waters, on the other hand, see no sunlight, but they contain nutrients galore. Theonly thing the nutrients need is the light and a few tiny ocean plants to kick-start an entireecosystem. The key is getting that nutrient-rich water to the surface. Along coasts and islands therising seafloor and stormy weather above do the trick. Winds stir surface waters and create

mixing currents that run deep and bring the deep waters up. Once those nutrients are in the sunlitupper waters, the nutrients are fertilizer for a burst of phytoplankton life the base of the entireocean food chain. At the top of that food chain are great white sharks and humpback whales,dolphins and seals, penguins and, of course, humans.

ProtectionBut coral reefs, mangrove swamps and other shallow-water habitats are more than just goodplaces to get food. They also protect coastlines where most people live. In places along the Sri


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Lankan coast, for instance, where corals have been illegally mined, the great Indian Oceantsunami of 2004 had no trouble barreling right into shore, taking lives and destroying property.Coral-protected areas saw much less trouble.

Then there's the Orissa Coast of India, where salt-tolerant mangrove trees were stripped away to

make room for shrimp farms. In 1999, the storm swells from a cyclone, normally stopped by themangroves, roared inland and drowned an estimated 10,000 people. With the majority ofhumanity living in coastal areas, the value of natural systems protecting the land is incalculable.

More than a quarter of Earth's tropical coastlines are protected by mangroves, but that number isshrinking. Since mangroves also serve as a natural sewage filter and home to many kinds ofcommercially valuable marine life, many conservationists are calling for more action to protectthem from development.

Coral reefs are also facing challenges.

Some have survived in place for more than 2 million years. The fish from coral reefs feeda billion people each year. However, the very same reefs are facing a triple threat: 1) destructive,unsustainable fishing methods, 2) coastal development and 3) global warming.

Hopeful SignsCoral animals, for all their tropical charm, don't really like very warm water. Global warmingcan cause waters to get too warm for some corals. They "bleach" and die. But some species maybe able to survive.

One recent study of corals in Hawaii found at least one coral species that bleaches whichmeans it loses its symbiotic algae but survives by switching to eating plankton for a living.

Yet another study in the Caribbean of fossilized corals show them to be the same species that arealive today despite evidence of many very warm water periods in between. Perhaps corals aremore resilient than we think.

Mangroves, though severely damaged and reduced worldwide, are getting renewed local support,as well as international attention. Ecuador, for instance, even provides incentives for shrimpfarmers to restore mangroves. In Bangladesh, villagers are employed by the government to plantmangroves in mudflats. These efforts have a long way to go to counteract a long history ofdestruction, but they are a good beginning.


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Flat, Grassy, Great Plains

Christopher Columbus was wrong: The Earth is flat, at least in places. There are seeminglyendless expanses of open ground, flat as the mind can imagine, found on every continent.Sometimes they are covered with grasses, ice or low shrubs that dot the land like stubble on avast expanse of dry skin.

The great plains of Earth are truly the oceans of the land. And like the seas, it's the little greenplants that make most of them work. Grasses are at the center of food webs that include rabbits,buffalo, yaks, camels, wolves and many other animals that live today on plains, or disappearedjust a few thousand years ago the blink of an eye in the history of the planet.

Lost Seas

The secret to making plains differs with the plain. The easiest way to get a plain, however, is tobuild it underwater. This is where the Great Plains of North America got started. More than 70million years ago these plains were the bottom of a shallow sea. That sea had spent about 500million years collecting sediments from 5,000 to 10,000 feet (1,500 to 3,000 meters) deep fromland to the east and west. It made for a very flat, soft seabed that stretched for thousands ofmiles.

The uplift of that land since then hasn't changed its basically flat character. But as dry land it wasnew territory and habitat that helped evolve some strange creatures like the Titanotheres,giant creatures with huge horns on their snouts. These lived 37 to 22 million years ago alongsideherds of camels, rhinoceroses, tapirs and horses, which are still found elsewhere in the world.

The Great Plains today stretch from Mexico and Texas, north into Canada 3.2 million squaremiles (8.3 million square kilometers) in all. Before Europeans came to North America, the GreatPlains were vast open grasslands between the western end of the great Atlantic forests and theRocky Mountains. They were too dry for trees, except in the lowest spots where water cancollect. Grasses took over and made a fine home for the great American bison, or buffalo, uponwhich many Native American tribes depended.


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No Easter BunnyAmong the things we can thank another vast plain for is the "Easter Bunny," indirectly. Bunniesof any kind, actually. It was on the plains of Mongolia in northern China that these beloved grasseaters evolved more than 20 million years ago. Lagomorphs, as these animals are called, evolvedto eat the grass, and drove the evolution of a set of smaller carnivores, like foxes and eagles, that

specialize in prey this size.

In all, the grassland plains of Inner Mongolia, China, encompass 306,000 square miles (792,000square kilometers), forming a 1,000-mile (1,600-kilometer) swath of grass across Central Asia.They support tens of millions of livestock animals in addition to wildlife.

Flat, Grassy, Great Plains

y Meet Plains Animalsy Link to Conservation Resourcesy Explore Planet Earth on AOL

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Ice AgeArctic tundra is another kind of plain. Deep sheets of ice covered the land during ice ages,scouring the surface flat. In frigid areas of the planet, tundra, characterized by thick, black mud

and permanently frozen subsoil, dominates the landscape. Trees won't grow in a tundra, but alack of water isn't to blame. It's the frozen ground. Even in the summer the sun thaws only a fewinches of soil, leaving the permafrost below the surface hard as stone. This frozen layer of earthdoes not absorb moisture well, so water runs off it like it does a rock. Not particularly welcomingto tree roots. Mostly a few short grasses, mosses, lichens and heath grow in the tundra in theshort summers.


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It's a Zoo Out ThereOf course, all plains vary in the animals and plants that inhabit them. There are the yaks, pikaand Tibetan foxes of the highest plain in the world, the Tibetan Plateau. Not very far away, justover the Himalayas, are the pygmy hogs, elephants and towering grasses of the Long GrassPlains of India. Two plains with very different inhabitants.

Then there's South America's 290,000-square-mile (750,000-square-kilometer) Pampas ofArgentina that once ran wild with rheas, nutrias, vizcachas, opossums and the endangeredPampas deer. Across the Atlantic there are lions, zebras and elephants on the African savannah another plain and more variety still on the South African veldt.

ThreatsOne of the greatest threats to the plains of Earth is climate change. A climate shift that sendsmore water to an arid plain, or warmth to tundra plains, would make those places morehospitable to trees, which would, in turn, dramatically change the rest of the flora and fauna. Onthe other hand, should climate change bring less rain to the Great Plains or the Mongolian

grasslands, it could lead to a permanent "dust bowl" condition. That would be an economic,environmental and humanitarian disaster.

At the moment, climate modelers haven't honed their predictions to say for sure what willhappen. The only thing certain is a change will occur.

Oddly enough, many of these plains may contain the seeds to their own salvation. Recentlybiologists in Minnesota have discovered that when native prairie grasses are allowed to grow ondepleted farmlands, the soils starts gaining carbon pretty quickly even of the grasses that aremowed which mimics grazing by buffalo or prairie fires by cutting away the upper part of theplant.

What's even more compelling is that the mowed grass can then be fermented and made intoethanol that can run cars and electrical generators. That means these grasses offer a fuel that is"carbon-negative," i.e., it lowers the carbon dioxide levels in the atmosphere and fights globalwarming. Not even corn ethanol can make that kind of climate-friendly claim.

What's more, in areas where prairie grasses are allowed to grow instead of cash crops, wildlife isalso coming back prairie chickens, pheasants and mule deer, for instance. The plains, itseems, may someday save not only themselves, but the planet.


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To Know a Jungle is to Love a JungleThere is, perhaps, no scene that conjures the word "primordial" more than that of a shadowy,steamy jungle. There are mysteries hidden everywhere, otherworldly screams, camouflagedpredators, noxious plants, stinging bugs, mold, decay and boggy impassable ground. It is, in theminds of many, the very thing civilization was invented to fend off.

Most of that sentiment comes from lack of familiarity with jungles, which are also called tropicalrain forests. To know a jungle, it turns out, is to love it. And there's the rub: Jungles are not easyto know. They are incredibly complex places, with most of their life in the leafy, limb-filledspaces above the ground. Humans did not evolve in a place like this, though native people have

shown that humans can adapt to it and live well if they learn the ways of the jungle.

Packed With LifeThe jungles of the world are jam-packed with species, despite covering only a few percent ofEarth's land area. They are the most diverse ecosystems on the planet. From New Guinea toCosta Rica to the Amazon and Africa, jungles can contain many hundreds of species of plantsand animals in just an acre. But diversity isn't their only asset.

Jungles protect land from erosion, generate rainfall by cooling the air above them, protect soils,prevent floods and contribute to groundwater supplies. To people who live in them, jungles alsoprovide fruit, nuts, medicines, meat and shelter materials in perpetuity that far exceeds the one-

time profit made by cutting down all the trees and selling the lumber. This is a fact that'sbecoming better understood worldwide.

Despite the growing appreciation for rain forests, of the ten percent of the world's wooded landsthat were cleared from 1970 to 1995, most were in the tropics. Between 1990 and 1995, treescame down in the greatest numbers in Latin America, with Africa and Asia right behind. Theworst deforestation tends to happen in countries with both lots of trees and dense populations,like Bangladesh, Pakistan, Jamaica and the Philippines.


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Besides demands for timber, fuel wood, charcoal and wood pulp, there is also a high demand forfarmland in these countries. So the jungles are cleared.

Hope for JunglesThings are not entirely bleak for the jungles, however. In the early 1990s, the world finally came

together to stop the destruction. The need for timber harvesters to start using sustainablepractices was made crystal clear by huge boycotts by consumers of tropical woods. By the end ofthe decade, more than 36 million acres of jungle had been certified sustainable by theinternational Forest Stewardship Council. What's more, certified timber sells for more.

Other arguments have also been used to protect the jungles. Their ability to absorb carbondioxide, for instance, helps to fight the greenhouse effect and global warming. There is also thehidden pharmaceutical and biodiversity value of jungles. Nature has spent millions of yearsmaking a dizzying array of jungle organisms, which produce an innumerable number of complexbioactive compounds that could do wonders for human health if only we had time to discoverand study them.

Finally, there is inherent value in primordial jungle for itself. The fantastic array of life found injungles, however unwelcome to most humans, offers something no human creation can evermatch the most complex show of interacting life on the planet. To many, that is not onlyintellectually stimulating and spiritually refreshing, but far too rich a treasure and too long in themaking to be sacrificed for a few more cords of timber.


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Freshwater: Earth's Life ForceImagine an entire planet where the universe's finest liqueur is boiled out of fermenting seas by abrilliant yellow star, distilled in the skies and rained back down on the land, forming lakes andrivers of the inebriating brew. The planet, of course, is Earth, and the liqueur is freshwater.

Without freshwater Earth's land masses would be barren, the continents might be in differentlocations, mountains would be far taller, and life virtually impossible. Earth's very character andappearance are the result of the planet being fairly drunk on this precious grog.

Liquid Destroyer

Luckily for us land animals, Earth can't help but make freshwater. It happens when the sun heatsand evaporates water from the oceans. The salts and other minerals are left behind, creating purewater vapor in the air. As it is carried higher to cooler air, it condenses and makes clouds, whichcan produce rain or snow when forced higher over land.

That's the water cycle, of course. It's something taught to every schoolchild for good reason.Not only does the water cycle give us the water we drink and use to grow food, it is also thecarver of coastlines, sculptor of mountains and the burier of seas. It might even play a criticalrole in plate tectonics, the process that keeps creating and destroying crustal plates that make upthe surface of the planet.

One of the more dramatic examples of what a few gazillon raindrops and snowflakes offreshwater can do over time is the Grand Canyon. Over the past 5 million years, the ColoradoRiver has just as steadily cut its way through the constantly bulging Colorado Plateau, makingthe mile-deep, 18-mile-wide, 200-mile-long Grand Canyon along the way.

By moving such gigantic masses of rock from one place to another, freshwater also removesweight from the Earth's crust in one place and weighs down others. By wearing away rocks ofthe Himalaya, for instance, rain and snow make the mountains lighter and actually speed up the


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rate at which the range buoys upward on the more plastic layer below the crust the zone calledthe mantle.

In turn, by affecting the pressure in the mantle, it's thought by some geophysicists that currentscan be generated in the mantle that influence how, when and where tectonic plates move. This

top-down theory to what drives plate tectonics makes freshwater a central player in the makingof every inch of Earth's surface today.

Watery CreatorBut freshwater does far more than move rocks around. Some of Earth's most unusual andbeautiful living landscapes are created and kept thriving by freshwater. The verdant and littleexplored Tepuis of Venezuela, for instance, are islands in the sky, loaded with species foundnowhere else. These plateaus and mountains are perpetually bathed in freshwater. In this uniqueecoregion, it's virtually always raining or socked in by thick, moisture-laden clouds.

Life in such torrentially wet places evolves to take quick advantage of their decaying neighbors.

Wait too long, for instance, and the next downpour will wash away what nutrients there are. Insuch a place, mold, fungus and large trees with broad, shallow roots form the basis of the foodchain.

Downstream from these water-rich places, forests and other highland rivers fill broad basins withforest waste and worn rock, piling up tens of thousands of feet of mud and silt for millions ofyears. The Mississippi River sediments deposited along the Gulf Coast are now so heavy thatthey are squeezing Earth's mantle. The sedimentation is believed to be one of the reasons NewOrleans and other parts of Louisiana are subsiding and becoming more vulnerable to hurricanesand sea level rise.

Grace ofW

aterDespite its great influence, all the freshwater that makes up the lakes, rivers, streams, creeks,marshes, potholes, bogs, fens, mires, swamps, ponds, billabongs, lagoons, mud holes andgroundwater of Earth has only recently been accounted for. Monitoring where water goes is a bigjob and can only really be done affordably for the entire planet from space.

NASA's Gravity Recovery and Climate Experiment (GRACE) satellites do this task bymeasuring local changes in gravity over time. All matter including water has mass andgravity. So when there's less water in a particular area, its gravity is slightly less. More water whether in lakes, streams or underground means the gravity is greater. GRACE has nowmanaged to watch as the continents swell and shrink with water on a seasonal basis showingEarth's water cycle actually at work on a global scale.

Bad & Good NewsFreshwater, however, is in trouble. Human activities have polluted and depleted freshwater inmany parts of the world. Wetlands have been drained to build and farm on. Nutrient levels inmany rivers and streams are so high from sewage, agricultural and industrial runoff, airpollution, and erosion that they are choked and starved of oxygen bad news for fish andinvertebrates that make for healthy streams and lakes.


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The good news is that conservationists have succeeded in protecting more than 800 of theworld's most vital wetlands all over the globe. It's even profitable. A 1991 study by theInternational Institute for Environment and Development found that a wetland in the arid northof Nigeria provided 30 times more profit from fish, firewood, cattle grazing and natural cropsthan if the water had been diverted to a large agricultural project. That's freshwater for you it's

heady stuff.

Forests: Towering Trees, Falling Leaves

If any one landscape on Earth has proved more useful to humanity it may be the forests. Theyhave provided lumber for homes and ships, firewood, food, medicines, and a plethora of folkstories and deities.

But forests' usefulness has been their undoing. Many of the world's great forests are either muchreduced by logging or on their way. North America's forests once stretched nearly the length ofthe continent, north to south, and from the Atlantic Ocean to the edge of the Great Plains.Likewise, Ireland and England were heavily wooded islands. You wouldn't know to look at themtoday. In fact, few places on Earth retain any virgin forests.

Evergreen OceanThe tsar of all forests on Earth is the taiga. It circles the planet from Sweden to Siberia to Alaskaand Canada. It's a cold, evergreen forest that is the largest single terrestrial biological zone on theplanet. It's where most of the world's trees live and it's populated almost entirely by evergreenspecies. Taiga is also a vast player in the seasonal changes in carbon dioxide levels in the entireatmosphere. Every spring, the trees awaken and start absorbing carbon dioxide and releasingoxygen. In the fall, the trees shut down and hibernate, and carbon dioxide from an array ofsources builds up.

Big as the taiga is, however, it's not able to keep up with the carbon dioxide humans have addedto the atmosphere since the dawn of the Coal Age and the Industrial Revolution. Carbon dioxide

is, after all, the No. 1 greenhouse gas.

Giant TreesSouth of the taiga are other forests, of course. But they are impressive for entirely differentreasons. The coast redwoods are the tallest trees in the world towering 300 feet above theground along the foggy coasts from southern Oregon down to Monterey County, Calif.


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These 20-million-year-old forests were extensively logged in the 1800s and early 1900s. Luckily,and unbeknownst to the loggers, these trees can sprout like weeds from their own roots. Todayyou can tell when you're in a second-growth redwood forest because there are always youngertrees growing in a ring around a decayed giant stump. They make an eerie circle of columns, likesome sort of strange sylvan temple.

Towering as the coast redwoods are, they're matchsticks compared to their Sierra Nevadacousins, the giant sequoias. These are the largest trees on Earth. They can get as tall as coastredwoods, but are far wider, some reaching 29 feet in diameter. The oldest giant sequoia is about3,200 years old, based on a coring of its annual growth rings.

When it comes to age, the giants have to concede to the far smaller, infinitely more twisted andhumble bristlecone pines of the eastern Sierra Nevada and other mountains of the Great Basin.By growing very slowly at the highest reaches of the mountains, some of these trees havesurvived for more than 5,000 years. That's halfway back to the last ice age.

Falling LeavesOf course, not all forests are evergreen. There are large broadleaf, deciduous forests all over theworld for example, in Russia, the eastern United States and the Rocky Mountains. All theseforests have one thing in common: They experience hotter, wetter summers than the taiga.

That extra water and summer heat makes broad, water-wasting leaves possible and speeds updecay of older leaves on the ground, which feed the soil and recycle many nutrients to the trees.

But dropping leaves is not only about cold. It's also about dryness. Winter in some places can bearid. That's why the leaf-dropping tactic is used by tropical trees in India and even some desertplants.

Future ForestsWhat all these forests have in common is that global warming is pushing their habitats poleward,or shrinking what little habitat they have. Since trees can't uproot themselves and walk to theright climate, they have to depend on their seeds dispersing farther toward the poles, germinatingalong the way to grow new forests. Needless to say, this is not something that happens overnight.

A more immediate threat is the demand for lumber, which has pushed loggers into even thevirgin taiga of Siberia. The battle for preserving these forests has just begun, and the peopletrying to save them cleave to the words of the 19th-century American writer Henry DavidThoreau: "... the pine is no more lumber than man is, and to be made into boards and houses is

no more its true and highest use than the truest use of a man is to be cut down and made intomanure."


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Excavating theWorld's Basements

There are monsters in the basements of the world: weird white crabs, pallid blind salamanders,hydrogen-eating bacteria and worms that glow in the dark. They live in caves furnished withbizarre and beautiful crystal chandeliers, limestone turrets and eerily dead-calm lakes.

It's a world without day and night and where the only circadian rhythm may be the coming andgoing of bats or birds, which supply the guano the manna on which most other cave lifedepends. These outsiders are a conduit for nutrients that ultimately come from a sun the cave-bound creatures never see.

No one knows how many caves there are on Earth. Probably millions. Many are undiscoveredand others are only partially explored. Likewise, there's no telling how many species ofspecialized cave organisms are out there that have yet to be discovered.

Just in the tristate area of Tennessee, Alabama and Georgia, for instance, there are about 15,000caves, not including hollows less than 50 feet long, says cave conservationist Lynn Roebuck ofthe National Speleological Society.

Swiss CheeseThe reason so many places on the planet are riddled with caves is that they all share anabundance of limestone. This rock is rather easily dissolved by even slightly acidic water, whichis common enough from water interacting with air and soils.

The limestone itself comes from eons of the remains of shells and skeletons of sea creaturespiling up on a seafloor. This means, of course, that all limestone was once at the bottom of longlost seas and was later lifted high and dry by tectonic forces. Once on land, rain and snowmelt


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filter down from the surface and gradually dissolve the limestone and carry it away. That has leftsome pretty amazing gaps in the ground.

A few caves have more extreme stories of excavation. Sometimes geology conspires to deliver apowerful dose of acid from sulfurous mineral deposits. That's the case at Lechuguilla Cave in

southeastern New Mexico, where the mineral mixture carried by groundwater into the cave hasproduced yellow-tinged formations not of limestone but of delicate gypsum a mineral made ofsulfur, calcium and water.

Lechuguilla is noteworthy for another reason: It's huge. Since its discovery in 1986, more than100 miles of continuous caves have been mapped, down to a depth of 1,567 feet. That makes itthe fifth longest cave in the world, the third longest in the U.S. and the deepest limestone cave inthe country.

Another cave with even greater doses of acid is Mexico's Villa Luz Cave. In Villa Luz sulfuricacid forms from rotten-egg-smelling hydrogen sulfide gas that bubbles up in springs. But acidity

is no problem to the bacteria that have evolved to live in its depths. In fact, hydrogen sulfide gasprovides chemical energy that feed bacteria just like in deep-sea hydrothermal ventcommunities.

A far less corrosive, but completely outsized, relative of Villa Luz is in China's Guangxi andChongquing provinces. The strange, mushroomy landscape of these parts is due entirely to a vastand monumental layer of regional limestone that is dissolving away. Hidden among the strangehills are remarkable sinkholes called tiankeng, or "sky holes," that are deep and wide enough tohide a few Empire State Buildings. These were all caves once, until their roofs collapsed. Todayvisitors can actually walk through caves beside an underground river to reach the bottom of oneof these sheer-walled holes in the earth.

Trouble From AboveLiving in the basement comes with some problems, of course. Bad stuff flows downhill.Chemicals from leaking sewage tanks, agricultural pollution and industrial waste can find theirway into caves, wreaking havoc with the rare life forms there.

A major threat to Lechuguilla, for instance, is proposed gas and oil drilling on nearby federallands managed by the Bureau of Land Management. Gas or fluids from such mining couldpotentially leak into the cave's many passages and poison cave life or even cause explosions,according to the National Park Service at Carlsbad Caverns National Park.

Cave pollution is also hazardous for humans who rely on water from caves. The Maya are said tohave gathered drinking water almost entirely from cave sources. In Tennessee, Roebuckremembers the case of a family that for at least three generations had been getting their waterfrom a cave. They called on Roebuck for help in finding the cause of a strange foam found on thecave water. The suspected cause was soap from a leaking septic tank.

"We're like Swiss cheese," said Roebuck, describing the underground nature of Tennessee. Tomake clearer to residents and decision makers how easily water from the surface can contaminate


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caves and waters used far and wide, "I usually take a sponge with me ... the water goes rightthrough it," she said.

More troubling, however, is vandalism. Volunteers like Roebuck and her husband spend a greatdeal of their time carefully brushing away spray paint and picking up garbage and other debris

deliberately left by humans in caves. They also work with many fellow cavers to clean upsinkholes places where even some city governments once thought it was OK to fill with anysort of waste. Unfortunately, sinkholes are the worst place to dump because they are often thegateways to cave systems.

Good NewsIt's not all bad news, however. More and more people are appreciating the importance ofprotecting caves for their own sake. Part of it might stem from the more general awareness ofgroundwater issues worldwide, says Roebuck.

"There seems to be more awareness about caves," said Roebuck. That includes people learning

about the correct ways to explore caves a pastime known as "caving." The NationalSpeleological Society lists good caving practices on their Web site. The bottom line is, "Cavesoftly."

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