1. Underline the correct words. Explain your choice.

2. Why is it necessary that the use of fertilizers, insecticides and weed killers should be strictly controlled? Give your opinion.

3. In what respect does urbanisation contribute to the destruction of agricultural land?

Forestry

Forests are an integral part of Earth’s life-support systems, playing a crucial role in regulating the atmosphere and climate through their ability to store carbon and drive local hydrological cycles. They protect soils from excessive erosion, regulate run-off and reduce the effect of floods and consequently silt loads in rivers. Natural forests are usually highly diverse ecosystems, supporting millions of species and providing human beings with a wealth of benefits. They are also an important part of the resource base for tourism and recreation, and have an inestimable cultural value as a source of beauty, contemplation and inspiration that finds expression in art, music, literature, dance and religion.

Unfortunately, forests everywhere are under increasing pressure from pollution and acid rain (although there are some doubts in this regard), unsustainable logging, the gathering of fuel-wood, bark stripping for traditional medicine, and clearing for agriculture and urbanisation.

In South Africa, indigenous evergreen forest is the smallest and most widely dispersed of the country’s seven major biomes, and covers just 0,25 per cent of the land surface. With the arrival of the European settlers in the 17^th century, these forests were heavily exploited, with many areas being completely destroyed or reduced to scrub. The remaining state-owned indigenous forests, particularly those in the southern Cape, are now carefully managed for sustainable yields of timber like yellowwood, stinkwood and ferns, although there is major concern in several areas about alien plant invaders and the encroachment of exotic species. Other indigenous forests in private hands are mostly not adequately protected and are rapidly diminishing.

As a result, ecosystems have been degraded, biodiversity reduced, soil eroded and valuable water resources wasted.

South Africa is an important exporter of especially pine, wattle and blue gum timber.

1. Suggest an alternative substance from which each of the following products could be manufactured:

2. Which functions performed by trees (forests) as a life-sustaining system cannot be replaced by anything else? (See par. 1)

A lien plant species

South Africa’s natural environment has already been invaded by more than 100 species of alien fauna and flora. It has caused widespread ecological damage and incurred losses to the value of several millions of rands in respect of lost agricultural potential and other land uses. Moreover, the extermination of alien species is a costly and time-consuming process.

The alien plants that have spread fastest over the past decades, eating into hundreds of thousands of hectares, include hakea, Australian Acacia, the Mauritius-thorn, paraffin-bush, lantana, water-lily, nasella tussock, various types of pine, and the jointed cactus.

Alien fish species such as trout and bagger have already eliminated the indigenous fish of various river systems, while extinct bird species such as the European starling and Indian myna birds have become a nuisance in urban and possibly rural

areas. Their exact numbers, however, are not known. Alien rats and mice are problem animals in human settlements, while the Argentine ant is a threat to South Africa’s fynbos as it eliminates the seed-dispersing indigenous ant.

South Africa’s most precious water resources are also badly affected by alien plants. River-bank habitats are particularly vulnerable to invasion and many of the upper and middle river courses have almost been completely overgrown with dense patches of silver and black wattle trees (Acacia species).

In fynbos-areas the water balance of mountain catchment areas have been upset by dense patches of alien plants, thus creating a far bigger fire hazard than the natural vegetation.

All seven of the most important biospheres are threatened by alien plants, with fynbos, savannah and wooded areas being affected most severely. Up to now efforts to kerb alien plants in the formal conservation areas of the sub-continent have met with varied success, when directed at alien trees and shrubs. Invasion by weeds and grasses are mostly ignored and little ecological information is available on this problem.

The eradication of alien species is a costly and time-consuming process.

1. Write short notes on one alien plant and one alien animal found in your area.

a) Alien plant

b) Alien animal

Some alien plants

Jointed cactus

Invasion by the jointed cactus hinder farming activities and cause the value of the land to depreciate. It diminishes the grazing potential of the veld.

Animals can become covered with sores and ulcerations as a result of the barbed thorns hooking into their flesh.

Oleander

Parts of the plant are poisonous for humans, birds and other animals.

Early signs of poisoning include sweating, loss of appetite, nausea, vomiting, dizziness, stomach cramps, etc. Serious cases can lead to death due to heart failure or paralysis of the respiratory system.

Port Jackson

The Port Jackson was originally planted to bind the sand on the Cape Flats.

The bark of the trees was initially used for the tanning of leather, but was later replaced by better types of bark.

The wood of the Port Jackson is softer en weaker than that of Rooikrans, which is a better sand-binder.

Lantana

This alien plant is so aggressive in the warmer regions of the Cape that it can choke trees of 10 metres in height.

Invasion in plantations hamper forestry activities. Animals eating the leaves may die.

Poisoning in humans may cause kidney failure, leading to death within three weeks.

Rooikrans

Rooikrans forms thick, impenetrable stretches of large shrubs or low trees with entangled crowns.

They cause a serious problem, as the germination suppresses the growth of indigenous plants, causing them to disappear.