Food Supply and Water as Limiting Factors

Chapters 37 and 38

Kwashiorkor: Sudden food deprivation due to natural or manmade emergencies produces a condition known as kwashiorkor. Apathy, swelling (oedema) of the extremities, torso and face, cracked, peeling, infection-prone skin and unnaturally blond, sparse hair are its visible characteristics.

malnutrition

Green revolution

The genes that sparked the Green Revolution came from unprepossessing wheat plants relegated to the ranks of agronomic curiosities. But their short, stiff straw and heavy seed heads caught the eye of ARS agronomist S. Cecil Salmon who was with Gen. Douglas MacArthur's headquarters in 1946 helping assess Japan's postwar agricultural problems.

Fresh water supply depends on the water cycle.

The cycle is disrupted due to climate change, erosion, deforestation and marginal land farming.

Irrigation requires ever increasing supplies of water

PROBLEMS CAUSED BY DAMS • HABITAT DESTRUCTION • LARGE LAKE FORMED PROVIDES BREEDING AREA FOR MOSQUITOS • SILTING UP OF THE DAM • REDUCED SOIL FERTILITY DOWNSTREAM • SPREADING OF WATER BORNE DISEASES BY IRRIGATION.

Loss of organic matter leading to decreased water holding capacity of soils and increased run off; · Loss of organic matter-rich soils reduces yields as crops are slower to germinate; · Loss of nutrients and crops themselves as a result of water and wind erosion.

Today, roughly 600,000 square kilometres or 15% of the Brazilian Amazon has been deforested, an area about equal to Spain and Portugal together Much of it is now in pasture to feed one of the fastest growing cattle herds in the world.

Land laid waste by deforestation and subject to erosion.

Most desertification happens as "runaway" phenomena which are irreversible on human timescales. That is to say, once desertification starts it is hard to stop

Crops fail and the soil may be blown away as dust

DROUGHT

• The number of people being fed by the UN World Food Programme (WFP) due to drought has more than quadrupled in the last four years, the food aid organisation said. WFP reports that more than 100 million people in over 20 countries currently suffer the effects of drought

CLIMATE CHANGE – SOME CAUSES

1988: Global warming attracts worldwide headlines after scientists at Congressional hearings in Washington DC blame major US drought on its influence.

We need energy to do things like drive a car, fly a plane, or make things in factories.

But we need to use energy wisely if we want to help slow global warming.

Effects of marine pollution:-

 Sewage effluent, or organically rich industrial effluent such as that from fish processing plants, presents a number of problems:  (i) Decomposition of organic matter causes a drop in dissolved oxygen, particularly in calm weather and sheltered bays. This can cause the death of marine plants and animals, and may lead to changes in biodiversity.

 (ii) Effluent, rich in nitrogen and phosphorus, results in eutrophication (overfertilization), which may cause algal blooms. These blooms can discolour the water, clog fish gills, or even be toxic, e.g. red tides. Microbial breakdown of dead algae can cause oxygen deficiencies.

 (iii) Pathogenic micro organisms cause gastric, or ear, nose, and throat infections, hepatitis, or even cholera and typhoid. Filter-feeding animals (e.g. mussels, clams, oysters) concentrate pathogens in their gut, so eating shellfish from polluted waters is a health risk.

•Oil spills smother plants and animals, preventing respiration. In seabirds and mammals it can cause a breakdown in their thermal insulation. Chemical toxicity can cause behavioral changes, physiological damage, or impair reproduction. Oil pollution is an eyesore, and cleanup and subsequent disposal of oily wastes is difficult.

•Pesticides, such as DDT, and other persistent chemicals e.g. PCBs, accumulate in the fatty tissue of animals. These chemicals can cause reproductive failure in marine mammals and birds.

•Ships often paint their hulls with anti-fouling substances, e.g. tributyl-tin (TBT), to prevent growth of marine organisms. These substances leach into water and, in high traffic areas such as harbours and marinas, can affect animal life. This has contributed to a call for a world-wide ban on the use of TBT. In the mean time, alternatives are being considered.

•Plastics kill many marine animals. Turtles, for example, often swallow floating plastic bags, mistaking them for jelly-fish. Animals are often strangled when they become entangled with plastic debris.