Hydrological implications of desertification: Degradation of South African semi-arid subtropical thicket
Luijk, G. van; Cowling, R.M. ; Riksen, M.J.P.M. ; Glenday, J. - \ 2013
Journal of Arid Environments 91 (2013). - ISSN 0140-1963 - p. 14 - 21.
succulent thicket - eastern cape - interception loss - land-use - runoff - savanna - carbon - water - transformation - sequestration
Almost half of the 16,942 km2 of South Africa's subtropical thicket with a substantial Portulacaria afra (spekboom) component has been heavily degraded by domestic herbivores. The subtropical thicket biome is a drought-prone and water-stressed area, and many of the region's watersheds comprise of eroded landscapes clothed in degraded spekboom thicket. The objective of this study was to determine the impact of degradation of spekboom thicket on hydrological processes. We hypothesised that degradation of spekboom thicket would reduce infiltration and, hence, reduce soil moisture retention and increase run-off and erosion. We tested this hypothesis by collecting data on rainfall, infiltration, soil moisture retention and run-off in degraded thicket, and – as a reference site – in an adjacent stand of relatively intact thicket. The results showed clear trends in the impacts of spekboom thicket degradation on hydrological processes. The more than hundred-fold lower infiltration in soils associated with degraded thicket relative to the soils beneath the intact, spekboom canopy, resulted in lower levels and less retention of soil moisture, almost double the amount of runoff, and an almost six-fold increase in sediment load. Thus, restoring degraded thicket will reduce erosion and likely improve baseflows, in addition to sequestering carbon.
The Road to Sustainability Must Bridge Three Great Divides
Aronson, J. ; Blignaut, J.N. ; Groot, R.S. de; Clewell, A. ; Lowry II, P.P. ; Woodworth, P. ; Cowling, R.M. ; Renison, D. ; Farley, J. ; Fontaine, C. ; Tongway, D. ; Levy, S. ; Milton, S.J. ; Rangel, O. ; Debrincat, B. ; Birkinshaw, C. - \ 2010
Annals of the New York Academy Of Sciences 1185 (2010). - ISSN 0077-8923 - p. 225 - 236.
ecosystem services - social-sciences - economic-growth - south-africa - ecology - policy - valuation - payments - working - world
The world's large and rapidly growing human population is exhausting Earth's natural capital at ever-faster rates, and yet appears mostly oblivious to the fact that these resources are limited. This is dangerous for our well-being and perhaps for our survival, as documented by numerous studies over many years. Why are we not moving instead toward sustainable levels of use? We argue here that this disconnection between our knowledge and our actions is largely caused by three "great divides": an ideological divide between economists and ecologists; an economic development divide between the rich and the poor; and an information divide, which obstructs communications between scientists, public opinion, and policy makers. These divides prevent our economies from responding effectively to urgent signals of environmental and ecological stress. The restoration of natural capital (RNC) can be an important strategy in bridging all of these divides. RNC projects and programs make explicit the multiple and mutually reinforcing linkages between environmental and economic well-being, while opening up a promising policy road in the search for a sustainable and desirable future for global society. The bridge-building capacity of RNC derives from its double focus: on the ecological restoration of degraded, overexploited natural ecosystems, and on the full socio-economic and ecological interface between people and their environments
Comment on "Neutral Ecological Theory Reveals Isolation and Rapid Speciation in a Biodiversity Hot Spot"
Etienne, R.S. ; Latimer, A.M. ; Silander, J.A. ; Cowling, R.M. - \ 2006
Science 311 (2006). - ISSN 0036-8075 - p. 5761 - 5761.
sampling theory - cape flora - alleles
Latimer et al. (Reports, 9 September 2005, p. 1722) used an approximate likelihood function to estimate parameters of Hubbell's neutral model of biodiversity. Reanalysis with the exact likelihood not only yields different estimates but also shows that two similar likelihood maxima for very different parameter combinations can occur. This reveals a limitation of using species abundance data to gain insight into speciation and dispersal