Earth System Science

1. Earth System Science • The Earth is a highly complex, interconnected system, with large numbers of unexpected feed-backs • ESS requires us to understand not only local processes within ‘familiar’ systems, but the often powerful connections that exist between different parts of the Earth system, including human socio-economic impacts

2. Global Change • We know that the Earth’s major systems are now changing more rapidly than at any time in the last half million years (at least) • Many of these changes are pushing the planet into hitherto uncharted territory – it has never been here before • Expect the unexpected

4. A Millennium Scale Perspective ... 2 1 N.H. Temperature (°C) 0 -1 1400 1000 1200 1600 1800 2000 Year Mann et al. (1999) GRL 26:759-762

5. Regions of rapid warming • Change in mean annual temperature in degrees Centigrade over the period 1950 - 1998. (Hansen)

7. Some specific African examples • Major processes elsewhere on the globe can impact on the African environment in very unexpected ways • Two related examples: The drought in the Sahel West African rainfall

8. The Sahel: Drought and Degradation Drought, land degradation and famine in the Sahel region of west Africa is, according to ’conventional wisdom’, a classic case of too many people and too much pressure on the land, which, when coupled with climate variability, creates a negative spiral of degradation and desertification. Or is it?

9. Decadal variations in Sahel rainfall and land use change Sahel summer rainfall (mm) displays huge decadal variations not seen in other tropical regions. ? Influence of land use change leading to desertification Natural vegetation Crop land Recent and projected deforestation in Africa shows land use change set to continue

10. Competing factors in decadal variations in Sahel rainfall • Vegetation changes (natural and man-made) have contributed to the prolonged drought through positive feedbacks • Drought also linked to decadal changes in Atlantic sea surface temperatures • Understanding decadal variability in this atmosphere-ocean-land system remains a challenge • But improved prediction for this marginal region is crucial for sustainability of water and food provisions.

12. Annual mean precipi- tation anomaly (mm d-1): (a) simulated by CSIRO GCM with sulphate aerosol forcing, (b) observed trend in mean annual precipitation (mm d-1 century-1) from 1901 to 1998. Source: Rotstayn and Lohmann, 2002, J. Climate, in press.

13. Controls on West African Rainfall: July - September • Sahel influenced by El Nino – drought in El Nino years • Guinea Coast influenced by equatorial Atlantic – heavy rain with warm ocean • Pre-season signals are strong for Guinea Coast, suggesting increased predictability

14. Three biological examples • West African coastal zone fisheries • Bush meat (which may be related to what happens in the coastal zone) • Coral-reef deaths

15. Trends in Fish Biomass off Northwest Africa, 1950-1999 Villy Christensen &The Sea Around Us Project Univ. of British Columbia, Vancouver, BC Marine fisheries, ecosystems and societies in West Africa: half a century of change Dakar, Senegal, June 24-28, 2002 A Fisheries Centre partnership with The Pew Charitable Trusts

16. How much fish? Excludes small pelagics

17. Northwest Africa 1950 - 1999

18. Fishing Catch intensity Biomass 1950 1999

19. Conclusions • Biomass of fish (excl. small pelagics) has decreased to less than 1/4 since 1950. • Fishing intensity increased 80 times since 1950, while catches only increased 18 times. • Fisheries of Northwest Africa are not sustainable A Fisheries Centre partnership with The Pew Charitable Trusts

20. Rosenberg A.A. (2003) Front. Ecol. Envir.

21. EU responsibilities • Europe is exporting its excess fishing capacity to West Africa and plundering the coastal-zone fisheries • EU boats frequently, illegally, come inside the 12 mile limit at night • The new ‘cash for access’ deals signed by the EU are still highly questionable

26. Fishing and bush meat • As local fisheries collapse, local communities are deprived of protein • Recent unpublished research by Justin Brashares suggests that collapsing West African fisheries are driving an increasing (and unsustainable) demand for bush meat in West Africa

28. Coral reefs • It is well known that corals throughout the world are being devastated by rising ocean temperatures • It is hardly known at all that rising atmospheric CO2 concentrations may also be having a direct, deleterious impact on corals, and other coastal-zone animals with calcareous skeletons

29. ECOLOGICAL EFFECTS OF THE 1998 EL NIÑO ON CORAL REEFS OF EASTERN AFRICA. David. Obura, Suleiman Mohammed, Helena Motta, Michael Schleyer, and Christopher Muhando GCRMN country and regional monitoring and reports Coordinated through CORDIO – Coral Reef Degradation in the Indian Ocean Mozambique – MICOA – Ministry for Environmental Coordination, Mozambique Tanzania – Institute of Marine Science, Zanzibar, with partners Kenya – CORDIO with WWF Prior, independent long term monitoring programmes Kenya - Coral Reef Conservation Project/Wildlife Conservation International South Africa – Oceanographic Research Institute

30. Sources: Temperatures: Chagos – C. Shepphard Maldives – S. Clarke, A. Edwards Kenya – D. Obura, T. McClanahan Zanzibar – C. Muhando South Africa – M. Schleyer Map: CHAMP website: http://coral.aoml.noaa.gov

31. CONCLUSIONS • THREATS • Coral bleaching caused by the El Niño Southern Oscillation of 1997-98 • the single largest threat to coral reefs ever documented in East Africa • degree of bleaching and mortality increased from South Africa (<1%) to Kenya (80%) • recovery of reefs by regrowth (1999/2000) and recruitment (2000), but variable, • Other threats continue • over-fishing, destructive fishing • pollution, human settlement and development • mining and shipping industry • MANAGEMENT AND CONSERVATION • Increasing number and types of MPAs – tourism, fish restocking, community/cultural issues • Increased attention to economic viability of MPAs • Increasing coastal zone management and cross-sectoral initiatives • POLICY AND LEGISLATION • Environmental acts and legislation • International conventions and institutions, e.g. UNEP.

32. AND IF THESE WERE NOT ENOUGHCO2 dissolves in sea-water • As it dissolves, it acidifies the water, which makes it more difficult for marine animals with calcareous skeletons to take up calcium from bicarbonate in sea water • There is growing evidence that this may now be impairing the growth of corals and other marine creatures

33. THE GLOBAL BIODIVERSITY CRISIS ‘Natural’ extinction rates should be 1-2 species per year globally Current rates are 10-100 times higher than this Looking out 50-100 years, hard to avoid conclusion that rates will rise to 1000 times ‘natural’, and possibly 10000 times Lawton and May (1995)

34. 40% of all terrestrial primary production (discarding much thereafter) 33-50% of all marine primary production 60% of all readily available fresh water (Pimm S.L. 2001) With a ‘doubling time’ of roughly 30-50 years in the human enterprise, this is unsustainable under a business as usual scenario WHY?EACH YEAR, HUMAN BEINGS NOW ‘TAKE’:

37. Thank you • Professor Callum Roberts (University of York) • Professor Julia Slingo (University of Reading) • Dr Will Steffen (IGBP, Sweden) • Professor Alan Thorpe (University of Reading)