Climatic Change

, Volume 109, Issue 3–4, pp 437–452 | Cite as

Pan evaporation and wind run decline in the Cape Floristic Region of South Africa (1974–2005): implications for vegetation responses to climate change

  • M. Timm Hoffman
  • Michael D. Cramer
  • Lindsey Gillson
  • Michael Wallace


In many regions of the world, increasing temperatures in recent decades are paradoxically associated with declining pan evaporation, but evidence is sparse for this trend from the southern hemisphere in general and sub-Saharan Africa in particular. In this study, we examined changes in pan evaporation and four other meteorological variables (rainfall, wind run, temperature and vapour pressure deficit) at 20 climate stations in the predominantly winter-rainfall Cape Floristic Region (CFR) of South Africa over the period 1974–2005. Our results show that pan evaporation has declined significantly at 16 climate stations at an average rate of 9.1 mm a − 2 while wind run has declined significantly at all climate stations by more than 25% over the study period. Annual rainfall has not changed significantly at any of the climate stations while maximum temperature has increased significantly at all but one climate station at an average rate of 0.03°C a. − 1 over the study period. The trends in vapour pressure deficit are mixed and no clear regional pattern is evident. Our results raise important questions about the predicted catastrophic impact that the projected changes in twenty-first century climates will have on the rich flora of the region. If evaporative demand has declined over the last 30 years in the Cape Floristic Region then it is possible that more water has become available for plant growth, infiltration and runoff despite the widespread increase in temperature. However, decreased pan evaporation and wind run combined with increased temperatures could potentially reduce transpiration and exacerbate heat stress of plants on increasingly frequent hot and windless days during the summer drought. Contrary to other predictions for the area, it is also likely that the changing conditions will decrease the frequency and/or intensity of fires which are an important component of the ecology of the fire-adapted CFR. Consideration of other factors besides changes in temperature and rainfall are essential in debates on the impact of climate change on the vegetation of this region.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Bomhard B, Richardson DM, Donaldson JS, Hughes GO, Midgley GF, Raimondo DC, Rebelo AG, Rouget M, Thuiller W (2005) Potential impacts of future land use and climate change on the Red List status of the Proteaceae in the Cape Floristic Region, South Africa. Glob Chang Biol 11:1452–1468CrossRefGoogle Scholar
  2. Brutsaert W (2006) Indications of increasing land surface evaporation during the second half of the 20th century. Geophys Res Lett 33(20):1410–1411. doi: 10.1029/2006GL027532 CrossRefGoogle Scholar
  3. Burn DH, Hesch NM (2007) Trends in evaporation for the Canadian prairies. J Hydrol 336:61–73CrossRefGoogle Scholar
  4. Cong ZT, Yang DW, aNi GH (2009) Does evaporation paradox exist in China? Hydrol Earth Sys Sci 13:357–366CrossRefGoogle Scholar
  5. Coudun C, Gégout J-C, Piedallu C, Rameau J-C (2006) Soil nutritional factors improve models of plant species distribution: an illustration with Acer campestre (L.) in France. J Biogeogr 33:1750–1763CrossRefGoogle Scholar
  6. Cowling RM, Pressey RL, Rouget M, Lombard ET (2003) A conservation plan for a global biodiversity hotspot—the Cape Floristic Region, South Africa. Biol Conserv 112:191–216CrossRefGoogle Scholar
  7. Cramer MD, Verboom GA, Hawkins HJ (2009) The importance of nutritional regulation of plant water flux. Oecologia 161:15–24CrossRefGoogle Scholar
  8. Eamus D, Palmer AR (2007) Is climate change a possible explanation for woody thickening in arid and semi-arid regions? Res Lett Ecol 37364:5. doi: 10.1155/2007/37364 Google Scholar
  9. El Nasr MN, Alazba AA (2010) Simple statistical equivalents of Penman-Monteith formula’s parameters in the absence of non-basic climatic factors. Arab J Geosci. doi: 10.1007/s12517-010-0231-1 Google Scholar
  10. Elith J, Leathwick J (2009) Species distribution models: Ecological explanation and prediction across space and time. Ann Rev Ecolog Evol Syst 40:677–697CrossRefGoogle Scholar
  11. Fu G, Charles SP, Yu J (2009) A critical overview of Epan trends over the last 50 years. Clim Change 97:193–214CrossRefGoogle Scholar
  12. Heikkinen RK, Luoto M, Araujo MB, Virkkala R, Thuiller WS, Martin T (2006) Methods and uncertainties in bioclimatic envelope modelling under climate change. Prog Phys Geogr 30:751–777CrossRefGoogle Scholar
  13. Hobbins MT, Ramirez JA, Brown TC (2004) Trends in Epan and actual evapotranspiration across the conterminous US: Paradoxical or complementary? Geophys Res Lett 31(13):L13503CrossRefGoogle Scholar
  14. Hoffman MT, Rohde RF (2007) From pastoralism to tourism: The historical impact of changing land use practices in Namaqualand. J Arid Environ 70:641–658CrossRefGoogle Scholar
  15. IPCCRao GSP, De US (2007) Climate Change 2007: synthesis report. In: Parry ML, Canziani OF, Palutikof JP, van der Linden PJ, Hanson CE (eds) Intergovernmental panel on climate change. Cambridge University Press, Cambridge, pp 24–73Google Scholar
  16. Jaswal AK, Rao GSP, De US (2008) Spatial and temporal characteristics of evaporation trends over India during 1971–2000. Mausam 59:149–158Google Scholar
  17. Jovanovic B, Jones DA, Collins D (2008) A high-quality monthly Epan dataset for Australia. Clim Change 87:517–535CrossRefGoogle Scholar
  18. Li CQ, Li BG, Hong KQ (2008) Climate change and its effect on reference evapotranspiration and crop water requirement in Hebei Province, China during 1965–1999. J Agrometeorol 10:261–265Google Scholar
  19. Liu B, Xu M, Henderson M, Gong W (2004) A spatial analysis of Epan trends in China, 1955–2000. J Geophys Res Atmos 109:L01812. doi: 10.1029/2004JD004511 CrossRefGoogle Scholar
  20. Liu B, Ma ZG, Xu JJ, Xiao ZN (2009) Comparison of Epan and actual evaporation estimated by land surface model in Xinjiang from 1960 to 2005. J Geogr Sci 19:502–512CrossRefGoogle Scholar
  21. Mackellar NC, Hewitson BC, Tadross MA (2007) Namaqualand’s climate: recent historical changes and future scenarios. J Arid Environ 70:604–614CrossRefGoogle Scholar
  22. McVicar TR, Van Niel TG, Li LT, Roderick ML, Rayner DP, Ricciardulli L, Donohue RJ (2008) Wind speed climatology and trends for Australia, 1975–2006: Capturing the stilling phenomenon and comparison with near-surface reanalysis output. Geophys Res Lett 35:L20403CrossRefGoogle Scholar
  23. Midgley GF, Thuiller W (2007) Potential vulnerability of Namaqualand plant diversity to anthropogenic climate change. J Arid Environ 70:615–628CrossRefGoogle Scholar
  24. Midgley GF, Hannah L, Millar D, Thuiller W, Booth A (2003) Developing regional and species-level assessments of climate change impacts on biodiversity: a preliminary study in the Cape Floristic Region. Biol Conserv 112:87–97CrossRefGoogle Scholar
  25. Midgley GF, Chapman RA, Hewitson B, Johnston P, DeWit M, Ziervogel G, Mukheibir P, Van Niekerk L, Tadross M, VanWilgen BW, Kgope B, Morant PD, Theron A, Scholes RJ, Forsyth GG (2005) A status quo, vulnerability and adaptation assessment of the physical and socio-economic effects of climate change in the Western Cape. ENV-S-C 2005-073, p 170. CSIR Environmentek, StellenboschGoogle Scholar
  26. Myers N, Mittermeier RA, Mittermeier CG, da Fonseca GAB, Kents J (2000) Biodiversity hotspots for conservation priorities. Nature 403:853–858CrossRefGoogle Scholar
  27. Nobel PS (2005) Physiochemical and environmental plant physiology. Academic Press, San Diego, CaliforniaGoogle Scholar
  28. Noble IR, Gill AM, Bary GAV (1980) McArthur’s fire danger meters expressed as equations. Austral Ecol 5:201–203CrossRefGoogle Scholar
  29. Olson DM, Dinerstein E (2002) The Global 200: priority ecoregions for global conservation action. Ann Miss Bot Gard 89:199–224CrossRefGoogle Scholar
  30. Pearce JL, Boyce MS (2006) Modelling distribution and abundance with presence-only data. J Appl Ecol 43:405–412CrossRefGoogle Scholar
  31. Pearson RG, Dawson TP (2003) Predicting the impacts of climate change on the distribution of species: are bioclimate envelope models useful? Glob Ecol Biogeogr 12:361–371CrossRefGoogle Scholar
  32. Rayner DP (2007) Wind run changes: the dominant factor affecting Epan trends in Australia. J Clim 20:3370–3394CrossRefGoogle Scholar
  33. Roderick ML, Farquhar GD (2002) The cause of decreased Epan over the past 50 years. Science 298:1410–1411Google Scholar
  34. Roderick ML, Farquhar G (2004) Changes in Australian Epan from 1970 to 2002. Int J Climatol 24:1077–1090CrossRefGoogle Scholar
  35. Roderick ML, Rotstayn LD, Farquhar GD, Hobbins MT (2007) On the attribution of changing pan evaporation. Geophys Res Lett 34:L17403. doi: 10.1029/2007GL031166 Google Scholar
  36. Roderick ML, Hobbins MT, Farquhar GD (2009a) Pan evaporation trends and the terrestrial water balance. I. Principles and Observations. Geogr Compass 3:746–760Google Scholar
  37. Roderick ML, Hobbins MT, Farquhar GD (2009b) Pan evaporation trends and the terrestrial water balance. II. Energy Balance and Interpretation. Geogr Compass 3:761–780Google Scholar
  38. Roth-Nebelsick A (2001) Computer based analysis of steady state and transient heat transfer of small-sized leaves by free and mixed convection. Plant Cell Environ 24:631–640CrossRefGoogle Scholar
  39. Stanhill G, Moller M (2008) Evaporative climate change in the British Isles. Int J Climatol 28:1127–1137CrossRefGoogle Scholar
  40. Thuiller W, Lavorel S, Midgley G, Lavergne S, Rebelo T (2004) Relating plant traits and species distributions along bioclimatic gradients for 88 Leucadendron taxa. Ecol 85:1688–1699CrossRefGoogle Scholar
  41. Valiantzas J (2006) Simplified versions for the Penman evaporation equation using routine weather data. J Hydrol 331:690–702CrossRefGoogle Scholar
  42. van Wilgen BW (2009) The evolution of fire and invasive alien plant management practices in fynbos. S Afr J Sci 105:335–342Google Scholar
  43. van Wilgen BW, Forsyth GG, de Klerk H, Das S (2010) Fire management in Mediterranean-climate shrublands: a case study from the Cape fynbos, South Africa. J Appl Ecol 47:631–638CrossRefGoogle Scholar
  44. Wand SJE, Steyn WJ, Theron KI (2008) Vulnerability and impact of climate change on pear production in South Africa. Acta Hort 800:263–272Google Scholar
  45. Wang Y, Jiang T, Bothe O, Fraedrich K (2007) Changes of Epan and reference evapotranspiration in the Yangtze River basin. Theor Appl Climatol 90:13–23CrossRefGoogle Scholar
  46. Warburton M, Schulze RE, Maharaj M (2005a) Is South Africa’s temperature changing? An analysis of trends from daily records, 1950–2000. In: Schulze RE (ed) Climate change and water resources in southern Africa: studies on scenarios, impacts, vulnerabilities and adaptation, pp 275–296. WRC Project K5/1430. ISBN No: 1-77005-365-4Google Scholar
  47. Warburton M, Schulze RE (2005b) Historical precipitation trends over southern Africa: a hydrology perspective. In: Schulze RE (ed) Climate change and water resources in southern Africa: studies on scenarios, impacts, vulnerabilities and adaptation, pp 325–338. WRC Project K5/1430. ISBN No: 1-77005-365-4Google Scholar
  48. Withers CS, Nadarajah S (2006) Evidence of trend in return levels for daily windrun in New Zealand. J Meteorol Soc Jpn 84:805–819CrossRefGoogle Scholar
  49. Yates MJ, Verboom GA, Rebelo AG, Cramer MD (2009) Ecophysiological significance of leaf size variation in Proteaceae from the Cape Floristic Region. Funct Ecol 24:485–492CrossRefGoogle Scholar
  50. Zar JH (1984) Biostatistical analysis. Prentice-Hall, Edgewood CliffsGoogle Scholar
  51. Zhang YQ, Liu CM, Tang YH, Yang YH (2007) Trends in Epan and reference and actual evapotranspiration across the Tibetan Plateau. J Geophys Res Atmos 112(D12):D12110CrossRefGoogle Scholar
  52. Zheng H, Liu X, Liu C, Dai X, Zhu R (2009) Assessing contributions to pan evaporation trends in Haihe River Basin, China. J Geophys Res Atmos 114:D24105. doi: 10.1029/2009JD012203 Google Scholar

Copyright information

© Springer Science+Business Media B.V. 2011

Authors and Affiliations

  • M. Timm Hoffman
    • 1
  • Michael D. Cramer
    • 1
  • Lindsey Gillson
    • 1
  • Michael Wallace
    • 2
  1. 1.Botany DepartmentUniversity of Cape TownRondeboschSouth Africa
  2. 2.Spatial Analysis Unit, Institute for Resource UtilisationWestern Cape Department of AgricultureElsenburgSouth Africa

Personalised recommendations