Drought

Drought is part of the Australian environment and affects more ecosystems than fire or flood. Australia is the driest inhabited continent and the climate is highly variable across the continent generally, as well as from year to year. Droughts can have a devastating effect on large areas of land and can destroy both agricultural and natural ecosystems. Drought can also degrade the land and affect the way land is used in the future.

What is drought?

There is no universal definition of drought - it depends on the climate of the area. A drought occurs when there is a prolonged, abnormally dry period in which there is not enough water for normal needs. The extent and severity of drought is monitored in terms of rainfall deficiencies and the impact it has on water levels, agricultural industries and natural ecosystems.

Drought in Australia

Droughts are a feature of the Australian environment. They occur regularly and are caused by climate change. Australia is prone to drought because of its geography. The continent is located under the subtropical high pressure belt which is an area of dry, stable air and clear skies. Areas of the continent such as the far north and south receive reasonably regular rain and the east coast receives moisture from the ocean. The rainfall over most of the country, however, is generally low and also highly erratic.

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Many droughts over eastern and northern Australia are caused by climate changes which accompany the El Niño-Southern Oscillation phenomenon which affects many countries on either side of the South Pacific Ocean. El Niño brings dry conditions and often drought to Australia, floods to South America and typically lasts about a year and can occur at intervals of between two and seven years. Droughts in the western areas and over much of the interior of Australia are normally caused by different factors but sometimes an El Niño related drought may extend across virtually the entire country. On these occasions, the effects of the drought on the ecosystems and on the agricultural industry and economy are widespread and particularly devastating.

Types of drought

Some droughts in Australia are long-lived while others are short and intense, but all types of droughts cause significant damage to the ecosystems. There is little chance that all of Australia could be in drought at the same time. The east coast, for example, may be in drought while the west coast could be enjoying plenty of rain. Some regional droughts are not related to El Niño events and are therefore harder to forecast.

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The Bureau of Meteorology has historical records that provide data on the climate of a region. These records show the average temperatures and rainfall and how much variation might be expected. Records show that severe drought affects some part of Australia about once every 18 years though the intervals between severe droughts have varied from four to 38 years. What the impact of global warming on Australia's weather patterns is, is yet to be fully determined.

The impact of drought

During drought, agricultural ecosystems suffer major damage. There is much loss of livestock and the growing of crops is disrupted. Declining productivity affects not only rural Australia but also the national economy. The impact of a drought may be felt for many years. Drought degrades the land and water quality and affects the way the land is used in the future. The loss of breeding stock means that it takes a long time to replace livestock that perished in the drought and there is often less money to start again. There is less vegetation so the soil is more vulnerable to erosion and there is often an increase in bushfires and dust storms. This has long-term implications for the sustainability of agricultural industries.

The drought also affects the natural ecosystems. Creeks and rivers dry up causing the organisms that rely on the water to perish. This in turn causes food shortages for animals higher up in the food chain. While farmers are able to hand-feed some livestock to keep them alive, much of the wildlife is left to starve. The risk of serious environmental damage, particularly through the loss of vegetation and soil erosion, has long-term implications for the sustainability of the agricultural industries as well as for the natural ecosystems.

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Another abnormal rainfall pattern that affects ecosystems is one that brings floods. The impact of floods will be explored in the next chapter.