Today's program is number 26 covering Lesson
Researcher wins presidential award for work on rain forests and rainfall By Denise Brehm News Office An MIT scientist whose work provided evidence that deforestation of specific sections of rain forest increases the prospect of widespread regional drought was recently selected by President Clinton to receive a Presidential Early Career Award for Science and Engineering.
The mountain rainforests are ring-fenced in protected parks. But a new study reveals that they are being damaged by lowland deforestation further down the hill. Cloud forests such those at Monteverde contain some of the richest assortments of tropical plants and animals in the world.
The clouds form when warm lowland winds blow up against steep mountains, causing the air to rise and condense moisture as clouds. Inscientists noticed that Monteverde's cloudbank was gaining altitude and failing to blanket the mountain in mist, possibly triggering the demise of several species of frogs.
Scientists linked the lifting clouds to rising Caribbean Sea temperatures due to global warming. But Robert Lawton of the University of Alabama in Huntsville has discovered that lack of lowland forest may be the decisive factor.
Little protection Despite the complex of public and private reserves littering Costa Rica, the lowlands have received little protection - only 18 per cent of the original vegetation from the beginning of the last century is still there. Lawton's team studied daily satellite photos and found far fewer clouds over the deforested lowlands that lie directly east of Monteverde compared to forests in neighbouring Nicaragua, where considerably less lowland trees have been destroyed.
The clouds in Costa Rica were also higher, as estimated from the clouds' shadows, the land elevation, and the known position of the Sun.
Coalminer's canaries The researchers fed their information into a computer model of the local climate and found that the clouds hung at metres over lowlands covered with pasture, but at metres over forested lowlands.
The model suggests the air over pastureland is warmer and drier, forcing it to travel higher into the sky before it forms clouds. Stephen Schneider, a Stanford University biologist who found the link to global warming, says both deforestation and global climate change could be having an impact.
He says cloud forests could act like "coalminer's canaries", giving an early warning of the damage local and global changes can have on an ecosystem. Science volp Related Articles Fencing off "biodiversity hot spots" will not protect species from extinction http: Probable impact of deforestation on hydrological processes.
The various ways in which the forest cover may influence the atmospheric and soil processes controlling the hydrological cycle are examined. Case studies of extensive deforestation affecting the rainfall pattern are reviewed.
Call it land use. It can be done for firewood, clearance for crops and livestock, or for export into the world market for logs and chips. Either way, transpiration volume dives, and downwind areas go dry. It's not the sole player in drought-creation, but it has its own effect.
Climate-driven deforestation will be having the same effect. Areas already stressed by drought may get even drier. Satellite measurements made from to show that the atmosphere in the subtropical regions both north and south of the equator is heating up.
As the atmosphere warms, it bulges out at the altitudes where the northern and southern jet streams slip past like swift and massive rivers of air. That bulging has pushed both jet streams about 70 miles closer to the Earth's poles.
Since the jet streams mark the edge of the tropics, in essence framing the hot zone that hugs the equator, their outward movement has allowed the tropics to grow wider by about miles.
That means the relatively drier subtropics move as well, pushing closer to places like Salt Lake City, where Thomas Reichler, co-author of the new study, teaches meteorology.
Details appear in Thursday's Science Express, the online edition of the journal Science.
The movement has allowed the subtropics to edge toward populated areas, including the American Southwest, southern Australia and the Mediterranean basin. In those places, the lack of precipitation already is a worry. Additional creep could move Africa's Sahara Desert farther north, worsening drought conditions that are already a serious problem on that continent and bringing drier weather to the countries that ring the Mediterranean Sea.
That could be very much related to this pattern that we are seeing in the atmosphere," said Isaac Held, a senior research scientist with the National Oceanic and Atmospheric Administration. He was not connected with the research.
A shift in where subtropical dry zones lie could make climate change locally noticeable for more people, said Karen Rosenlof, a NOAA research meteorologist also unconnected to the study.
Her own work suggests the tropics have actually compressed sinceafter growing wider over the previous 20 years. Reichler suspects global warming is the root cause of the shift, but said he can't be certain.
Other possibilities include variability and destruction of the ozone layer.Arid Region Landforms 18 and Eolian Processes In most deserts, running water operates only occasionally, so it may seem odd that water rather than wind is the chief.
• Deposition- the process of deposing someone or something Hydrologic and Geomorphic Processes in Deserts Section 2: Desert Landforms Shaped by Winds • Mushroom Rock- Sand-blasting is the reason for the creation of mushroom rocks.
The North Slope of Alaska's Brooks Range also receives less than mm ( in) of precipitation per year and is often classified as a cold desert. Other regions of the world have cold deserts, including areas of the Himalayas and other high-altitude areas in other parts of the world.
Orographic deserts - deserts that receive little moisture due to the "rain shadow" effect of nearby mountains, e.g., Basin and Range of Nevada and eastern Oregon's deserts.
Desert Processes Aeolian processes - caused by the wind (remember, the wind is a low density, low viscosity fluid). As you follow the Tropics of Cancer and Capricorn, thirty degrees on either side of the equator, you will see, distributed with suspicious regularity, a brown band of drylands circling the planet, a sere belt warding off greener climes: the deserts of the world.
Food Deserts: Causes, Consequences and Solutions. define and examine the characteristics of food deserts; identify the causes and consequences of food deserts; A food desert is defined on the site as a “low income census tract where a substantial number or share of residents has low access to a supermarket or large grocery store .