What climate changes are anticipated in southern Africa?
Surface air temperature anomalies (deviations from a long-term average,
in this case 1901-1950) most of over southern Africa (shaded green box)
in degrees Celsius for the
20th and 21st centuries. The black line shows observed temperature
anomalies from 1906 to 2005. The thick red line shows a range of
temperatures in which computer model simulations "expected"
the anomalies to fall within. The shaded orange area presents
an "envelope" within which temperature anomalies are expected from 2001
to 2100 based on a possible future scenario (called "A1B") which
economic growth together
with rapid technological advancement, strong globalization, global
population growing until 2050 and then declining, and a
balanced use of fossil intensive and non-fossil energy sources.
Source: Adapted from IPCC Fourth Assessment Report (2007), Working Group 1: The Physical Science Basis, Chapter 11, Figure 11.1
Different places are experiencing different effects of climate change, and this trend is going to continue into the future. Some parts of southern Africa will have less rain and more wind, others will have more rain, and it will be hotter and more humid everywhere. Even the length of the growing season for plants is changing, which affects agricultural and ecosystem productivity.
For the land area in the shaded green box on the map to the left (12-35°S and 10-52°E) and the particular scenario (named "A1B") described in its caption, the median (average) of 21 model simulations when comparing the period 1980-1999 with the period 2080-2099 was:
What is meant by impacts of climate change?
There is a succession of "knock-on" impacts from primary impacts on the atmosphere caused directly by human activities (air pollution). These lead to secondary impacts on the climate (such as rising temperatures or more heavy rains) which, in turn, induce third order impacts on land and water. These may include failure of crops and spread of malaria due to higher temperatures and/or waterlogged soils, for example. Fourth order impacts result from these - for example, increased human hunger due to crop failure and increased mortality from disease.
Generally, the climate impacts anticipated for southern Africa are similar to those being experienced around the world: general warming (day and night temperatures all year round); changes in rainfall timing and quantities; changes in seasons (longer summers); increased climate variability (e.g. floods, droughts and heatwaves); higher sea-levels; and increasing frequency and intensity of extreme weather events like hail storms, gale force winds and so on.
These impacts lead to higher order impacts such as:
|Current and possible future impacts
and vulnerabilities associated with climate variability and climate
change for Africa.
Source: Adapted from IPCC Fourth Assessment Report (2007), Working Group 2: Impacts, Adaptation and Vulnerability, Chapter 9, Figure 9.5
Who (and what) is most vulnerable to these impacts?
Vulnerability is dependent on various things, including:
Farmers are generally more sensitive to droughts than urban residents, for example, due to their direct dependence on rainfall for their livelihoods. And whilst commercial farmers may suffer bigger financial losses due to drought than small scale farmers, the latter group are generally more vulnerable because they have fewer resources (or less capacity) to survive that same drought. Clearly the magnitude of a climate impact, such as the duration of a drought, also plays a part in determining vulnerability.
Usually, the most vulnerable people are the poor because they have limited adaptive capacity. Other particularly vulnerable groups include the sick and elderly, those poorly educated and isolated (e.g. remote rural communities), and women-headed households.
Some sectors are more vulnerable to climate change impacts than others; agriculture, health and water are good examples of particularly vulnerable sectors. Similarly, some systems are more vulnerable than others. For example, fynbos ecosystems are more vulnerable to climate change than savanna ecosystems.
How might climate change affect water supplies in southern Africa?
Freshwater systems will be impacted mainly by increasing variability in rainfall, as well as rising sea levels. Groundwater and surface water (e.g. in rivers and lakes) will decrease, and increased evaporation from the ground will leave the soils more salty, thereby limiting plant growth. By mid-century, 50-100 million people in southern Africa may experience water shortages. Sea-level rise will cause increasing salinisation of groundwater and estuaries, leaving less freshwater for humans, for agriculture and for ecosystems.There will also be more intense floods. Although these will to some extent relieve the water shortages, the floods will be damaging to infrastructure (e.g. bridges) and result in more water-borne disease. Moreover, diseases will spread more easily as water temperatures increase in response to global warming.
The IPCC is confident that the overall net impact of climate change on water resources and freshwater ecosystems will be negative due to diminished quantity and quality of available water.
What are the implications of climate change for food security in southern Africa?
Food security is not just about having enough food in a country or region; it is also about people being able to access that food and about the nutritional status of the food that people eat. In southern Africa, it is expected that climate change will diminish productivity of cereal crops and livestock. There may be local extinctions of various species of fish in rivers, lakes and coastal areas that near to the edge of where they naturally occur. Other marine resources will also be negatively, such as those associated with coral reefs (on the east coast of Africa). Thus communities dependent on fish and other aquatic resources will be impacted. Salt water intrusion into groundwater in low-lying coastal plains may kill or stunt the growth of coastal crops. All these impacts together may cause southern Africa to become more dependent on food imports to sustain its population, hence reducing food security.
As crop yields decline with changing temperature and rainfall, pressure to cultivate unsuitable land or to farm in an unsustainable manner will rise. For example, increasing heat stress will significantly increase water requirements for livestock, resulting in overgrazing near water points. This may cause land degradation and endanger biodiversity. Changes in the frequency and intensity of fires, pests and diseases is also expected to reduce food security in southern Africa.
How will human health in southern Africa be affected by climate change?
Climate change already contributes to the problem of disease and premature deaths worldwide, and this is projected to become worse over time especially in low-income countries. In particular, the IPCC found with high confidence that there will be an increasing number of people suffering death, injury and disease from heatwaves, floods, storms, fires and droughts.
Heart and lung illnesses will most likely increase as ground-level ozone (a toxic gas), smoke and airborne dust increase in response to warmer temperatures. Higher temperatures may also lead to the spread of malaria across densely populated parts of Zimbabwe and also onto the South Africa highveld. Dengue fever, also carried by mosquitoes, may also spread into areas of southern Africa where it previously did not occur.
Aside from the direct impacts of floods on human health, such as drowning, there are other flood-related impacts such as the outbreak of diarrhoea as water supplies become contaminated.
Some human health impacts of climate change are mentioned under the question above relating to food security; diminished food availability, food access and nutrient content will result in more malnutrition and starvation.
What climate impacts will there be for ecosystems in southern Africa?
Climate change has already begun impacting on ecosystems around the world, mostly to their detriment. Projected climate change is a threat to many species and even some ecosystems, as identified by both the Millennium Ecosystem Assessment (of 2005) and the IPCC. Quite aside from their own intrinsic value, healthily functioning ecosystems are essential to human well-being. According to the southern African Millennium Ecosystem Assessment, at least four of the eight Millennium Development Goals will not be achieved in the region unless ecosystem services (i.e. the benefits people derive from ecosystems) are stabilised; this cannot happen with the current rate of climate change. Moreover, rising temperatures facilitate the spread of "invasive alien species" (like weeds) which themselves are a significant threat to ecosystems and agriculture.
The geographic extent of Cape Fynbos may be reduced by around two-thirds, with over half of its species becoming extinct due to temperature rise. In addition to this, higher levels of carbon dioxide in the air will increase the risk of wildfires in Fynbos areas.
Ocean warming and acidification through absorption of carbon dioxide from the air will continue to increase, thus affecting marine organisms including plankton and coral and all the associated organisms that are dependent on them. Coastal fisheries and the tourism industry will probably be affected negatively. Riverine ecosystems will also be affected through lower river flows and higher water temperatures. Warming events, such as heat waves, aid the proliferation of algae in rivers which consumes much of the oxygen in the water, thus harming other species, and produces toxins which cause human illness. Fish yields in Lake Tanganyika have already declined by around 30%, a trend that is expected to worsen as temperatures continue to rise.