Climate and resources

Climate is the average of weather conditions at a place or in a region, usually recorded as both the mean (average) and the extremes of temperature, precipitation, and other relevant conditions. Resources are the factors and characteristics of the natural environment that people find useful, including climate, land, soil, water, minerals, and wild vegetation. Thus, climate is itself a natural resource, and it interacts with or affects the character or quality of other resources and their exploitation or development.

Background

Climate can be seen as the most basic or primary of natural resources in that it affects other resources to a greater degree than it is affected by them. Perhaps the best evidence of this is in the nature and distribution of wild vegetation. (The term “wild vegetation” is preferable to “natural vegetation” because humankind has had dramatic impacts upon the character and distribution of plants.) Temperature, moisture, and solar radiation are the major factors determining the plant species that will grow in a region, and the major global vegetation types (forest, shrub, grassland, desert, and tundra) reflect climatic controls. Microclimates are in turn created within the vegetation: trees provide shade and thus a slightly cooler temperature than in the surrounding region. However, microclimates exist only in minuscule portions of the main climatic region; consequently, climate influences vegetation more than the reverse.

Solar radiation is the source of energy that drives the Earth’s and its circulation system; therefore, it is the basic in determining differences in climate. The sun’s rays are vertical at some times of the year only in the tropics, between the Tropic of Cancer (23.5° north latitude) and the Tropic of Capricorn (23.5° south latitude). These lines determine where the greatest heat supply is found; regions poleward of about 40° north and south latitudes actually have a net loss of reradiation to outer space and depend upon a heat supply from the tropics, which is carried poleward by the general circulation of the atmosphere.

Equatorial Climates

The general circulation is the average wind flow at the surface of the Earth and is driven by the surplus of solar radiation in the tropics. By definition, tropical climates do not experience freezing temperatures, have the least variation in length of day, and consequently experience the least “seasonality” of any latitudes. Seasons here are characterized more by precipitation contrasts—“dry” and “wet”—rather than by summer and winter temperatures. The greatest combination of heat and moisture resources on the Earth’s surface, especially important in creating the conditions under which the tropical rain forest flourishes, is near the equator.

Rates of weathering of bedrock and soils are greatest in the equatorial region, because is a function of the availability of heat and moisture. It follows that the depth to which and soil are weathered and leached (mineral plant foods dissolved and removed by flow) is greater here than elsewhere on the Earth’s surface. Continuously high temperatures work against carbon storage in the soils; organic carbon storage requires recycling from wild vegetation. of organic matter by exposure to the sun’s rays follows the clearing of tropical forests. Under wild vegetation conditions, where the rainforest canopy protects soils from raindrop impact, rates are not as high as one would expect from the intense rain showers. However, on sloping land, the soils become saturated and flow downslope, often catastrophically in disastrous landslides. Where wild vegetation has been removed by human activity, in farming or especially in urban centers, erosion and mass wasting (landslides) are exacerbated during rainy seasons and cause considerable loss of life and property damage.

With increasing distance from the equator, the tropics experience more pronounced seasons, particularly in moisture resources. Precipitation totals decline, and drought risk increases. Dry seasons are expected annually because of the shifting of the general circulation of the atmosphere. The timing and extent of this shift determine whether a region experiences drought (a period when significantly lower-than-average precipitation causes low levels of streamflow and increased stress on vegetation, both wild and cultivated). East and South Asia are most affected by shifting atmospheric circulation and the resultant wet and dry seasons, or “monsoons.” Africa also has pronounced wet and dry seasons as a result of shifting atmospheric circulation patterns; droughts in the Sahel and East Africa are a consequence of the failure of rains to reach the region in time to support agriculture and grazing. Droughts in this part of the world result in famine: An estimated one million people died in the Sahelian droughts of the late 1960s and 1970s. Thus, climate must be defined in terms of both averages and extremes; the latter result in hazards that have dire consequences for the inhabitants of the affected region.

The probability of a drought hazard occurring increases as precipitation averages decrease (an inverse relationship) and is exacerbated by the fact that most tropical rainfall falls as intense thundershowers, which are spatially highly variable. One farm may be drenched by rain while its neighbors continue to be tormented by drought. In addition to drought risk on the margins of the tropics, the major climatic hazard is the tropical cyclone, which goes by various names, most commonly hurricane or typhoon. These cyclones, too, rarely affect the equatorial zone but frequent the tropical transition to the subtropics and midlatitudes. The movement of tropical cyclones is easterly in their early and middle stages, following the general circulation known as the trade winds.

The Subtropics

The types of climates that exist poleward of the tropics depend on the side of the continent: West sides are deserts or drylands; east sides are the humid subtropics, a transition zone with cooler temperatures and more risk of frost with greater distance from the equator. The humid subtropics are also subject to occasional easterly flow weather systems, including tropical cyclones. While they represent a serious hazard, claiming both lives and property, these easterly systems also deliver moisture and thus reduce the possibility of drought. The generally warm temperatures and moist conditions make these climates some of the most productive for crop growth, even exceeding the potential of the tropics. of soils and high erosion rates on cleared fields are nearly as great a problem as in the tropics, as is the rapid rate of organic decomposition.

The west coast drylands, which include all the world’s major deserts—Sahara, Atacama, Kalahari, Australian, and North American—are a consequence of the general circulation of the atmosphere, which chooses these locations to make the swing from the prevailing westerlies of the middle latitudes to the easterly trade winds. In the process, high atmospheric pressures prevail, and winds are descending or subsiding, and therefore warming—just the opposite of the conditions required for rainfall. The drylands may extend deep into the continents, as in North America and especially in Africa and Asia; the dryness of the Sahara also blankets the Middle East and extends northward into Central Asia. Temperatures along the equatorward flank of these five major dryland zones are tropical, and where irrigation water is available, tropical plants may be grown. Most of the drylands are subtropical or midlatitude, and thus they experience frost as well as drought hazard. Weathering and erosion are appreciably less in the drylands, owing to the absence of moisture, and leaching of the soils is virtually absent. Instead, salts in the soils can build up to levels that are toxic to most plants—another climate-related hazard.

The Midlatitudes

The midlatitudes extend from the subtropics to the polar climates of the Arctic and Antarctic, with temperatures following a transition from warm on the equatorward flank to too cold for agriculture nearer the poles. This is the realm of the westerlies, with extratropical cyclones delivering most of the weather. It is a zone of contrasting conditions, year by year and day by day, ranging from warmer than average to colder than average, from too humid to too dry on the inland dryland border.

Thus, the hazards of extremes of temperature and precipitation often dominate life, as tropical and polar air masses converge to create the cyclones that march from west to east. Drought risk is most important on the dryland border and results in the world’s great grasslands. Summer heat may be a hazard on occasion, and nearly every winter brings storms with freezing rain, high winds, and heavy snowfalls, particularly on the eastern sides of the continents. The eastern sides are also afflicted with such intense summer storms as the tornadoes of North America (a winter phenomenon in the adjoining humid subtropics), and the tail end of hurricanes and typhoons, as these become caught up in westerly circulation and curve poleward again. The Arctic fringe of the midlatitudes is too cool for significant agriculture but yields the great subarctic forests of Canada, Scandinavia, and Russia. Polar climates are too cold for all but a few hunters and fishers and people engaged in extractive industries or scientific research.

Bibliography

Anderson, Bruce T., and Alan Strahler. Visualizing Weather and Climate. Hoboken, N.J.: Wiley, in collaboration with the National Geographic Society, 2008.

Bryson, Reid A., and Thomas J. Murray. Climates of Hunger: Mankind and the World’s Changing Weather. Madison: University of Wisconsin Press, 1977.

Crausbay, Shelley D. "A Science Agenda to Inform Natural Resource Management Decisions in an Era of Ecological Transformation." BioScience, vol. 72, no. 1, Jan. 2022, pp. 71-90, doi.org/10.1093/biosci/biab102. Accessed 23 Dec. 2024.

Grigg, D. B. The Agricultural Systems of the World: An Evolutionary Approach. New York: Cambridge University Press, 1974.

Le Roy Ladurie, Emmanuel. Times of Feast, Times of Famine: A History of Climate Since the Year 1000. Rev. and updated ed. Translated by Barbara Bray. New York: Noonday Press, 1988.

Lindwall, Courtney. "What Are the Effects of Climate Change?" Natural Resources Defense Council (NRDC), 24 Oct. 2022, www.nrdc.org/stories/what-are-effects-climate-change#environment. Accessed 23 Dec. 2024.

Ruddiman, William F. Plows, Plagues, and Petroleum: How Humans Took Control of Climate. Princeton, N.J.: Princeton University Press, 2005.

Sivakumar, Mannava V. K., and Raymond P. Motha, eds. Managing Weather and Climate Risks in Agriculture. New York: Springer, 2007.

Strahler, Alan H., and Arthur N. Strahler. Introducing Physical Geography. 4th ed. Hoboken, N.J.: J. Wiley, 2006.

Strahler, Arthur N., and Alan H. Strahler. Elements of Physical Geography. 4th ed. New York: Wiley, 1989.