Impacts of Climatic and Atmospheric Change

According to Terblanche, (1994) in terms of human impacts, warmer temperatures in South Africa may lead to:

• More deaths, especially among the elderly, due directly to heat waves.
• Greater risk of epidemic infectious illnesses, such as malaria, due to an expansion of suitable habitat (for mosquitoes that carry malaria). Malaria epidemics have been linked to both temperature and rainfall in South Africa, and appear to show a steady increase overall since 1993 (Table 1.5).

Increased ozone levels in the lower atmosphere (resulting from nitrous oxides and hydrocarbons reacting in the sunlight) could lead to respiratory health effects. This is hard to document since these are not diseases for which national statistics are maintained, and respiratory effects can have many causes Terblanche, (1994).

Depletion of upper atmosphere stratospheric ozone will result in more of the harmful ultra-violet B radiation reaching ground level. This could lead to increases in skin cancer and cataracts, and possibly reduction in the effectiveness of the immune system (Terblanche, 1994).

While the long-term average concentrations of sulphur dioxide, nitric oxide, tropospheric ozone and respirable particulate matter are within international health guidelines, there may be short periods where the guidelines are exceeded. During these episodes, sensitive individuals (such as those who already have respiratory problems) are likely to be affected .

Although most people associate air pollution with urban, outdoor environments, some of the highest pollution concentrations are found in rural, indoor environments. About 2.8 million people die each year in developing countries due to indoor exposure to particulate matter and 0.2 million due to outdoor exposure to suspended particulate matter (Schwela D, 1998). Comparison of urban to rural areas in terms of indoor exposure reveal that about 1.9 million people may die each year in rural areas, compared to some 0.6 million in urban areas. The impact (morbidity and mortality due to air pollution) in South Africa has not been quantified. It is especially a problem for children of low-income families, who live mainly in rural areas and in inadequate housing.

Effects on ecosystems:   

Depletion of upper atmosphere stratospheric ozone will result in more of the harmful ultra-violet B radiation reaching ground level. Ultra-violet B radiation causes damage to the photosynthetic pathways and genetic structure of plants.

Rising carbon dioxide levels have a generally stimulatory effect on plant growth, and especially on water use efficiency. The rise to 360 ppm now, from 270 ppm two centuries ago is not known to have had detrimental effects on ecosystems, but continued rapid rise above the levels which have been experienced in the past million years could have impacts on the climate system. These are very hard to predict, as are impacts on sea level rise and direct impacts on plant performance and biodiversity (IPCC, 1995).

Methane is not toxic at the levels experienced, but is a powerful greenhouse-effect gas. It also reacts with other hydrocarbons and oxides of nitrogen to form tropospheric ozone, which is toxic to plants and animals. Tropospheric ozone levels on the highveld occasionally and briefly exceed the levels known to cause plant damage.

Sulphur dioxide is toxic to plants and animals, and the toxic levels are also occasionally and briefly exceeded in areas of Gauteng and Mpumalanga. There have been no conclusively proven cases of chronic damage to vegetation as a result. Pine needles on the Mpumalanga escarpment sometimes show banding which may be associated with high levels of sulphur dioxide and/or ozone.

Sulphur dioxide is transformed in the atmosphere into sulphuric acid, and nitric oxide into nitric acid. These two acids are deposited in South Africa mostly as fine particles in combination with other substances found in the atmosphere (dry deposition), but also as wet deposition (acid rain). If the rate at which this acid is added to ecosystems exceeds the natural buffering capacity (especially of the soil), the soil will become acid and less able to support plant growth, and aluminium will leach into the water bodies, where it is toxic to aquatic life. This critical rate of deposition is almost certainly exceeded in parts of South Africa, especially on the escarpment east and south of Gauteng and the industrial areas of Mpumalanga (Kuylenstierna and Hicks, 1998). Evidence of changes to the soil and water quality as outlined above which can be linked indisputably to acid deposition alone is not available. It is possible, however, that it could occur within a few decades if the current levels of sulphur emissions continue. Shallow, acid, sandy soils are the most prone to acidification. An increase in nitrate in river water is likely to be the first symptom of nitrogen saturation, which accompanies acid deposition (see Freshwater).

A decrease or increase in rainfall in South Africa will have an effect on the distribution and productivity of ecosystems. The changes in grazing potential between wet and dry years are an example. There is no evidence to date of a long-term trend in Southern African rainfall, either up or down. There is evidence for an upward temperature trend. This could lead, in the longer term, for example, to the extinction of isolated plant species on mountain peaks, and to the invasion of the central grasslands by savanna trees. More trees in the grassland would reduce the grazing potential of the land. The presently-observed changes are sufficiently small for agriculture to be able to adapt to them.

Impacts of sea level rise:   

Even a moderate increase in the mean sea level substantially increases the probability that coastal structures, such as piers and sea walls, will be overtopped and damaged when severe storms coincide with high tides. These structures are designed with a certain failure probability (for instance, a one-in-a-hundred year event). They will fail much more frequently than this unless costly preventative adjustments are made.

The generally steep coastline of South Africa means that very little land will be flooded as a result of rising sea level, and the planning laws which restrict development within 1 km of the beach will help to limit damage. Estuaries will experience greater salinity, and coastal fresh-water aquifers will be contaminated to a greater degree by salt water. Very few communities in South Africa depend on coastal aquifers for their water supply. For these communities, water quality will deteriorate and the costs of providing good quality water will increase.

>     Climatic and Atmospheric Changes: Response

There is also information about Climatic and Atmospheric Change in the following reports:
Metropolitan reports:
	Cape Metropolitan Council (1998 edition)		Durban Pilot Study
	Greater Johannesburg Metropolitan Council (1999 edition)		Greater Pretoria Metropolitan Council (1999 edition)