Why Southern Africa?
Central and southern Africa are experiencing large-scale social, economic and political changes
that are affecting the land use and land cover across the regionís subtropical, semi-arid and arid
ecosystems. Specifically, significant impacts have been caused by increasing populations,
population migration, industrial development, water shortages and the widespread practice of less
efficient or unsustainable agricultural techniques. For example, increased political stability
provided a basis for more rapid economic development. Tourism and the mineral sector of heavy
industry, in particular, are expanding rapidly.
The atmosphere of the region is also experiencing significant change. Its thin layer acts as an
integrating mechanism whereby locations thousands of kilometres apart are linked through the
strength and persistence of a regional circulation feature known as the southern African
anticyclonic gyre. The trace gases and aerosols transported within this gyre come from three
principal sources: the burning of fossil fuels and other industrial activities; biomass burning in
wildfires and domestic hearth fires; and natural processes in the terrestrial and aquatic
ecosystems of the region. Specifically, the burning of fossil fuels in mining, industrial and
domestic activities are in part responsible for rising levels of atmospheric aerosols and trace gases
(Held et al., 1996; Sivertsen et al., 1995).
These emissions are augmented by those from some of
the most extensive biomass burning in the world, most of which is associated with savanna
burning, domestic fuelwood consumption, and agricultural practices (Crutzen and Andreae, 1990;
Helas and Pienaar, 1996; Scholes et al., 1996; Justice et al., 1996: Hulme et al., 1997; Chanda et
al., 1998). Together with strong biogenic emissions (Harris et al. 1996; Parsons et al. 1996;
Levine et al. 1996; Guenther et al. 1996; Thompson et al., 1996), these emissions may be altering
the biogeochemical cycling of essential nutrients in the region (Garstang et al., 1998).
From preliminary analysis of the available data it appears that no single emission source
dominates. This has yet to be rigorously tested, however. Among other phenomena, the
interaction and transformation of emissions within the atmosphere contribute to the development
of an elevated tropospheric ozone anomaly over the western edge of the sub-continent and
adjacent tropical South Atlantic ocean in the late dry season and early spring (Fishman et al.
Previous research initiatives focused separately on ecological and climate issues contributed
much to our understanding of discipline-specific processes.
They also stimulated the formulation of difficult and complex questions that perhaps can
only be answered with the coordinated,
interdisciplinary approach of SAFARI 2000. Much more attention now needs to be given to
understanding the linkages between the controlling and impacted processes, particularly those
occurring over relatively large spatial and temporal scales.
In 1992 NASA participated in the Trace - A / Southern Africa Fire - Atmosphere Research Initiative (SAFARI) 1992 (Andreae et al. 1994). SAFARI 92 was the Southern African component and focused on the factors controlling the process and distribution of biomass burning as well as the chemistry, transport and source strength of the products of biomass burning (Lindesay et al. 1996). During SAFARI several partnerships were developed between US and southern African scientists. The continued development of these relationships has culminated in the proposed SAFARI 2000 experiment. SAFARI was chosen as a rallying acronym for the initiative, centered on the millennium and with a heritage of international collaboration within the region. The project has met with preliminary endorsement from the IGAC BIBEX group, the original umbrella organization for the SAFARI 92 campaign. From the NASA side the activity will be similar to the SCAR (Smoke Cloud Aerosol and Radiation) experiment series (Kaufman et al. 1998) involving aircraft and in situ experiments but with stronger terrestrial ecosystems, land cover and land use change and satellite validation components than before.
Central and southern Africa have undergone and continue to undergo large changes in social, economic and political environments that contribute to large-scale changes in land use and land cover within their respective ecosystems. The opening up of southern Africa due to the absence of war and political strife has led to economic development, especially in the sector of heavy industry. Energy generation to drive mining and metallurgical industries, as well as the industrial processes themselves, contribute to high levels of aerosol and trace gas emissions (Held et al., 1997; Sivertsen et al., 1995). Additionally, this region of Africa is subjected to some of the highest degrees of biomass burning in the world, most of which is associated with human population pressures on regional ecosystems (Crutzen and Andreae, 1990; Helas and Pienaar, 1996; Scholes et al., 1996; Justice et al., 1996). These anthropogenic perturbations, along with a strong, largely understood source of biogenic emission processes (Harris et al. 1996; Parsons et al. 1996; Levine et al. 1996; Guenther et al. 1996) and a large natural variability in both regional climate and ecosystem processes combine, primarily through manipulation of surface aerosol and trace gas emissions, to effect changes in the biogeochemical cycling of the region.
In addition to the partnerships developed during and after SAFARI-92, much progress has been made recently in scientific research concerning changes in land cover and land usage, atmospheric circulations and transports, biogeochemistry, and ecosystem functioning, in southern and central Africa. The implementation of the IGBP Terrestrial Transects program (Koch et al., 1995), the creation of the IGBP Miombo network (Desanker et al. 1997), the IGBP Kalahari Transect (Scholes and Parsons, 1997), the IGBP BIBEX (Biomass Burning Experiment) SAFARI/TRACE-A field campaigns (Andreae et al., 1994; Lindesay et al., 1996; Fishman et al., 1996), the formation of the Southern African Atmospheric Research Initiative (SAARI) alliance as well as the involvement of IGAC's Biosphere-Atmosphere Trace Gas Exchange in the Tropics (BATGE; Guenther et al. 1995; 1996) and Deposition of Biogeochemically Important Trace Species (DEBITS) programs within the region are all examples of such progress.
Although these projects have all contributed to the understanding of discipline-specific objectives, exploration of linkages between and the integration of information from each of the specific disciplines to form a more complete and interdisciplinary understanding of the functioning of southern and central Africa ecosystems and the regional atmosphere has been lacking. It is envisaged that advances in the understanding and modeling of the biogeophysical systems associated with NASA EOS validation activities, as they relate to regional and global environmental change in southern Africa, will result from an interdisciplinary approach that involves international collaboration.