IGBP Report

The Kalahari Transect is proposed as one of IGBPs Transects (see Koch et al. 1995 [IGBP Report 36]). It is located so as to span the gradient between the arid subtropics and the moist tropics in southern Africa, a zone potentially susceptible to changes in the global precipitation pattern. Its focus is the relationships between the structure and function of ecosystems and their large-scale biophysical and human drivers (climate, atmosphere and land use). The Kalahari Transect spans a strong climatic gradient in southern Africa, from the arid south to the humid north, while remaining on a single broad soil type, the deep sands of the Kalahari basin. The vegetation ranges over the length of the transect from shrubland through savannas and woodlands to closed evergreen tropical forest, with land uses ranging from migratory wildlife systems, through pastoralism, subsistence cropping to forestry. The objectives of the Kalahari Transect activity are to: build an active network of regional and international researchers around the issue of ecosystem structure and function in savanna woodlands undergoing climatic and land use change; quantify the current and future role of southern African savanna woodlands in the global carbon, water and trace gas budgets and the degree of dependence of these budgets on climate and land use change; develop a predictive understanding of future changes in southern African savannas and woodlands on sandy soils, including their capacity to deliver forage, timber and other products. A five year project is proposed, commencing in 1997. The project revolves around four themes: vegetation structure, composition and dynamics; biogeochemistry, trace gas emissions and productivity; resource use and management and water and energy balance. These themes define the minimum set of processes necessary for understanding of the Kalahari system

The Southern African Regional Science Initiative (SAFARI 2000) : wet season campaigns

The Southern African Regional Science Initiative (SAFARI 2000) involved two wet season and one dry season field campaigns. This paper reports on the wet season campaigns. The first was conducted at five sites along the Kalahari Transect in Zambia (Kataba Forest) and Botswana (Pandamatenga, Maun, Okwa River Crossing, Tshane) during February 2000 and concentrated primarily on characterizing the land surface with respect to exchanges of matter and energy with the atmosphere. The second, conducted in February 2001, focused on fluxes of water, gases and energy between the canopy and the atmosphere at Maun, Botswana, and at Skukuza in the Kruger National Park, South Africa. Eddy covariance measurements at Skukuza and Maun were designed to collect a near-continuous record of the seasonality and inter-annual variability in savanna carbon, water and energy exchanges in representative savanna ecosystems. This paper gives brief descriptions of the sites, the measurements made, and the methods used. It highlights some preliminary results, particularly from the first campaign, and outlines the next stages of the SAFARI 2000 projec

How do we best synergise climate mitigation actions to co-benefit biodiversity?

Acknowledgements We thank Yuka Otsuki Estrada for help in designing and producing the table, and all other authors of the IPBES-IPCC report on the scientific outcome of the IPBES-IPCC co-sponsored workshop on biodiversity and climate change (Pörtner et al., 2021) for cross-cutting discussions during preparation of this analysis. Although this paper is based on the report of the IPBES-IPCC co882 sponsored workshop, the views expressed here represent the individual views of the authors. We would also like to thank the scientific steering committee of the IPBES-IPCC co-sponsored workshop, review editors, the IPCC and IPBES Secretariat, especially Anne Larigauderie, and Technical Support Units. In memory of our friend and co-author, Bob Scholes, who sadly died during the preparation of this synthesis, and who will be sorely missed by all.Peer reviewedPostprin

A full greenhouse gases budget of africa: Synthesis, uncertainties, and vulnerabilities

This paper, developed under the framework of the RECCAP initiative, aims at providing improved estimates of the carbon and GHG (CO2, CH4 and N2O) balance of continental Africa. The various components and processes of the African carbon and GHG budget are considered, existing data reviewed, and new data from different methodologies (inventories, ecosystem flux measurements, models, and atmospheric inversions) presented. Uncertainties are quantified and current gaps and weaknesses in knowledge and monitoring systems described in order to guide future requirements. The majority of results agree that Africa is a small sink of carbon on an annual scale, with an average value of −0.61 ± 0.58 Pg C yr−1. Nevertheless, the emissions of CH4 and N2O may turn Africa into a net source of radiative forcing in CO2 equivalent terms. At sub-regional level, there is significant spatial variability in both sources and sinks, due to the diversity of biomes represented and differences in the degree of anthropic impacts. Southern Africa is the main source region; while central Africa, with its evergreen tropical forests, is the main sink. Emissions from land-use change in Africa are significant (around 0.32 ± 0.05 Pg C yr−1), even higher than the fossil fuel emissions: this is a unique feature among all the continents. There could be significant carbon losses from forest land even without deforestation, resulting from the impact of selective logging. Fires play a significant role in the African carbon cycle, with 1.03 ± 0.22 Pg C yr−1 of carbon emissions, and 90% originating in savannas and dry woodlands. A large portion of the wild fire emissions are compensated by CO2 uptake during the growing season, but an uncertain fraction of the emission from wood harvested for domestic use is not. Most of these fluxes have large interannual variability, on the order of ±0.5 Pg C yr−1 in standard deviation, accounting for around 25% of the year-to-year variation in the global carbon budget. Despite the high uncertainty, the estimates provided in this paper show the important role that Africa plays in the global carbon cycle, both in terms of absolute contribution, and as a key source of interannual variability

Book review:Serengeti III: Human Impacts on Ecosystem Dynamics, edited by A.R.E. Sinclair, C. Packer, S.A.R. Mduma & J.M. Fryxell. Chicago University Press,Chicago. 2008. Pp. 522. Price US$45. Paperback. ISBN: 9780226760339

Serengeti III: Human Impacts on Ecosystem Dynamics, edited by A.R.E. Sinclair, C.  Packer, S.A.R. Mduma & J.M. Fryxell. Chicago University Press,Chicago. 2008. Pp.  522. Price US$45. Paperback. ISBN: 978022676033

Convex Relationships in Ecosystems Containing Mixtures of Trees and Grass

The relationship between grass production andthe quantity of trees in mixed tree-grassecosystems (savannas) is convex for all or mostof its range. In other words, the grassproduction declines more steeply per unitincrease in tree quantity at low tree coverthan at high tree cover. Since much of theeconomic value in savannas is ultimatelyderived from grass, and the main mechanismcontrolling the tree-grass balance is dependenton the production of grassy fuel for fires,this non-linearity has the effect of creatingtwo savanna configurations. One has a low treedensity and supports a viable grazingenterprise, while the other has dense treecover and a frequently non-viable grazingenterprise. The non-linearity is suggested hereto have two main sources: the geometry of thespatial interaction between tree root systemand grasses, and the effect of differingphenology (the time course of leaf areaexposure) on the acquisition of water andnutrients. The existence of the non-linearityreduces the resilience of thegenerally-preferred “open” configuration, andincreases the resilience of the less-desirable“closed” configuration. Copyright Kluwer Academic Publishers 2003competition, primary productivity, resilience, savannas,