SAVANNA

Any tropical or subtropical grassland characterized by scattered trees or shrubs, a pronounced dry season and periodic bush fires.

THE SAVANNA ECOSYSTEM Savanna is a landscape with a more or less continuous grass layer

and scattered woody plants. Savannas are characterized by a continuous cover of perennial grasses, with an open canopy of drought, fire or browser-resistant trees, associated with tropical areas where there is at least one pronounced dry season.

It develops where seasonal forest would form but edaphic conditions or disturbance prevents the establishment of extensive tree cover. Savannas are effectively sub-climax ecosystems maintained due to edaphic, fire and/or herbivore influence. Edaphic savannas form on free-draining substrates that inhibit the growth of hydrophilous trees. The influence of fire, both from natural and human origins, creates ecosystems dominated by plants adapted to survive frequent and periodic burning.

Humans have interacted with savannas for millennia contributing substantially to the contemporary composition and distribution.

SAVANNA… The balance between tree cover and grassland is crucial, influencing

plant and livestock production, as well as ecological systems such as the water cycle. The amount of tree cover in such savannas is determined not by rainfall, but by disturbances such as fires and animals feeding. Changes in the tree-grass balance would have significant impacts on plant and livestock production, biodiversity, and the water and carbon cycles.

Savannas are the most extensive biome in the tropics. These extremely dynamic coupled socio-ecological ecosystems are shaped by a long history of interaction with humans, fire, climate and wildlife, particularly herbivores. Increasing human population growth, climate change, atmospheric change and resource use impact on savanna composition, distribution and function bring a host of challenges. These impacts are compounded by political, land tenure and economic shifts — all factors that will bring more challenges.

SAVANNA… Forest and savanna fires contribute to climate change, both by

causing loss of vegetation and soils that serve as carbon stocks and by releasing of carbon (and other greenhouse gases) to the atmosphere by burning. As global warming increases, these fires are likely to get more intense and extensive, and may result in significant ecosystem changes that would affect biodiversity through species loss or changes in species composition. In southern Africa, changes in the fire and grazing regimes during the past century are thought to have increased woody plant density over large parts of the region.

Climate change has affected the global distribution of vegetation from the distant past and will likely affect it into the future. On the other hand, changes in the distribution and structure of the vegetation may influence climate. The manifold aspects of climate change lead to quite diverse responses of soil moisture and the corresponding grass and shrub cover.

IMPACTS OF CLIMATE CHANGE

1. Altered precipitationDrought is known to significantly affect savanna and grassland ecosystems. The reductions in plant cover and productivity in the Southern African savanna in response to drying trends is possible. Moreover, increases in drying of the savanna biome in the next century will be compounded by other pressures such as conversion to agriculture. Climate change is also likely to alter the frequency, intensity, seasonality and extent of vegetation fires needed to maintain some Southern African savannas. On the other hand, absence of fire due to strong rains robustly influences tree dominance at the regional scale while at a continental scale fire suppression increases biomass in vegetation by a more modest 13%.

IMPACTS…

2. Increase in temperatureThe increase in temperature may induce larger evapotranspiration in tropical savannas. That, in turn, could result in reduction in the amount of soil water, even when rainfall does not change significantly. That factor by itself can trigger the replacement of the present-day potential biomes by other vegetation types which may be more adapted to less soil water.

IMPACTS…

3. Increase in CO2 concentration

Elevated temperature and atmospheric CO2 concentrations predicted longer growing periods, higher allocation to roots, higher fecundity, more biomass and a dramatic shift toward tree dominated biomes. Elevated CO2 may encourage bush encroachment in much of the eastern part of the country, in combination with the increasing minimum temperatures this will lead to a switch from grassland to woodlands and savannas, with concomitant loss of grassland specialists.

IMPACTS…

4. Water ScarcityThe savanna areas experience water stress because of the uneven distribution of the resource especially in the tropical savanna area. Prolonged and severe droughts lead to low water levels in rivers, underground aquifers and reservoirs, affecting the hydrology, biodiversity and water supply. Climate change will exacerbate water scarcity problems, particularly in the semi-arid areas as well as pollution of water supplies. Prolonged droughts can have serious impacts on agricultural production. Even long dry spells during the rainy season are sufficient to reduce agricultural production, thus seriously impacting on livelihoods of the savanna communities.

IMPACTS…

5. Exacerbate the difficulties in land use by livestock grazingAlthough savanna ecosystems cover a wide range of climatic conditions, they are mostly located in arid or semi-arid areas, where they are susceptible to the land-degradation dynamics associated with overgrazing, erosion-induced losses of soil nutrients, and a consequential diminishing in many ecosystem functions. The savanna biome is used predominantly for livestock grazing or wildlife management, including nature-based tourism. Shrub encroachment and the loss of perennials strongly reduce the carrying capacity of rangelands for livestock. This will intensify difficulties in land management, since livestock grazing itself has led to landscapes dominated by unpalatable shrubs.

IMPACTS…

6. WildfireThe influence of fire, both from natural and human origins, creates ecosystems dominated by plants adapted to survive frequent and periodic burning. Forest and savanna fires contribute to climate change, both by causing loss of vegetation and soils that serve as carbon stocks and by releasing of carbon (and other greenhouse gases) to the atmosphere by burning. As global warming increases, these fires are likely to get more intense and extensive, and may result in significant ecosystem changes that would affect biodiversity through species loss or changes in species composition. In southern Africa, changes in the fire and grazing regimes during the past century are thought to have increased woody plant density over large parts of the region.

IMPACTS…7. Desertification

Desertification will cause conversion of perennial grasslands to savannas dominated by annual grasses. Such changes have already occurred in the Kalahari Gemsbok National Park in South Africa, where Landsat imagery shows increases in exposed soil surface. Drying, increased wind speeds and temperature increases due to climate change will reduce vegetation cover and cause the reactivation (where sand becomes significantly exposed and moves) of Southern African desert dune systems as early as 2039. Even under a medium emissions scenario, significant dune dynamism is predicted for parts of the northern dune fields (which include those in Namibia), which are currently heavily vegetated. There will be expansion of desert and arid land vegetation at the expense of grassland and savanna in Namibia. Climate change is expected to exacerbate desertification (Schlesinger et al., 1990; Middleton and Thomas, 1997). Furthermore, overexploitation of vegetation that is typical in semi-arid drylands (UNDP, 1998; ICCD, 1999), in synergy with climate change, will further increase habitat loss and hence loss of biodiversity, ecosystem services, and the potential for adaptation.

IMPACTS…

8. Loss of habitat & reduction in population of savanna animals On land, animal biodiversity in Africa is concentrated in the savannas and

tropical forests. Loss or alterations of terrestrial habitats by climate change will likely impact these species. Climate change is predicted to reduce population success amongst African arid savanna raptor species. Similarly, there will be reductions in species ranges for almost 80 percent of the 179 in South Africa, including many savanna species.

Climate change could alter the range of many African antelope species. Population declines of three ungulate species in Kruger National Park, South Africa, suggest that reduced summer rainfall, possibly related to regional warming, is likely to result in their local extinction if warming continues, especially as boundary fencing inhibits their migration.

Climate change could induce a decline of nyala (Tragelaphus) and zebra (Equiferus), which could not adapt to climate induced habitat changes (Dixon et al. 2003). In Namibia, increased aridification associated with climate change is likely to cause three mammalian extinctions at a national level, range declines from ten species (such as lechwe and giraffe) and range increases for two arid adapted species: the gemsbok and springbok.

IMPACTS…

Modified vegetation and agriculture The effects of global climate change such as altered

precipitation patterns and increased temperature leading to reduced water availability will likely increase this risk. At the same time, an elevated atmospheric CO2 level could mitigate the effects of reduced water availability by increasing the water use efficiency of plants.

Climate change affects agricultural production in a diverse and complex manner. Increase in temperature escalates soil chemical reactions leading to increase in decomposition of organic matter and therefore release of greenhouse gases into atmosphere. This process also results in loss of fertility thus affecting yield negatively.

FLORAL COMPOSITION

Grasses Herbs Vines Trees

FAUNAL COMPOSITION

Herds of animals Numerous species of birds Lower animals such as ants & termites

SAVANNA PEOPLE

Population Indigenous people Grazing Tourism Industries & employment

LANDSCAPE & CLIMATE

Wide range of climate conditions

Almost every major geological & soil type occurs

CLIMATE CHANGE

THREATS / IMPACTS

Altered precipitation Increased temperature Exacerbate the difficulties in land use by livestock grazing Wildfire Desertification Reduce population of many savanna animals Modified vegetation Rising sea level, stronger tropical cyclones & increased

intensity of oceanic storm surges Various industries will be affected Disease outbreaks Species migration

MITIGATION

Make use of geothermal & solar energy Massive reforestation & agro-forestry

farming programs Fire management Carbon sequestration

ADAPTATION

Plants may facilitate their own growth by promoting infiltration Shading of plants lead to reduced evaporation Many plants such as water lilies survive the dry season by going into

a “resting phase” allowing their leaves to die but alive as roots, tubers or rhizomes

Some plants also set seeds, some of which are extremely long-lasting

Many of the reptiles have adopted to withstand periods of low food supplies

Many crocodiles, frogs & turtles of the savanna land survive dry period by burrowing

Deep cracks in parched clay and mud provide shelter for a number of animals like rodents

People shift their agricultural activities & their settlements to new locations

NATIONAL LEVEL

Formulation of climate change policy Establishment of an integrated drought

monitoring & information system Development of policies & institutions

that support adaptation at community levels & encourage private sector participation

Resource allocation

ADAPTATION

Enhance collective/participatory decision – making process

Diversification of income sources & livelihood systems

Introduction of collective security arrangements

Provision of knowledge, technology, policy, institutional & financial support

Prioritization of local adaptation measures & provision of feedback to stake holders

COMMUNITY LEVELADAPTATION

TECHNOLOGICAL SOLUTIONS

Geothermal power plant Solar energy arrester Small holder irrigation system Integrated rain water harvesting

system Low-cost pumps & water application

methods

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