South African Environmental Observation Network
South African Environmental Observation Network
The South African Environmental Observation Network is a science network of people, organisations and, most importantly observation platforms, that perform Long-Term Ecological Research in South Africa and its surrounding oceans. The SAEON is of global importance as an innovative approach in ecology to understand environmental change and to determine the impact of anthropogenic forces at multiple scales but it is a remarkably complex challenge to statistically discern between ubiquitous natural variability and exogenous forcing. The SAEON constitutes a national government response to the World Summit on Sustainable Development and is a component of the GEO . The SAEON has become the leader in environmental science and observation in South Africa but has been criticised for taking a long time to establish, a situation which was inevitable in view of SAEON's multiple stakeholder corps. It has also been raised that the cost of replicated experimental treatments across SAEON sites will be high Wikipedia.
News Article | May 19, 2017
A study using data stretching back several decades has produced the first empirical evidence that increasingly hot, dry summers driven by climate change are having a negative effect on the Cape’s unique fynbos. The findings also raise questions about the effect this climate change impact could have on the Western Cape’s water catchment areas in the long-term, GroundUp reported. South African Environmental Observation Network (SAEON) researcher Jasper Slingsby, a biodiversity scientist who led the research project, said while scientists had known for some time that the changing climate would likely affect ecosystems, they did not know how much the climate needed to change before any ecosystem impacts could be detected. Now, they have found an interaction between fire and climate change that is causing a loss of fynbos species. Backtrack to 1966, when botanist Hugh Taylor, who recognised the value of long-term monitoring, permanently marked out 54 plots across Cape Point, recording all plant species that occurred in each. In 1996, two UCT botanists carried out a second plant survey and in 2010 Slingsby and authors did a third. Slingsby said it was clear that there had been a decline in the number of species, but the cause was not as clear. ALIEN PLANTS Researchers identified that alien plants were a cause. There are good historical records of alien plant distribution at Cape Point. Although the aliens had been cleared 30 years earlier, the study found those plots which had had dense stands of aliens had clearly lost more fynbos species. Slingsby said while they did not know the exact mechanism that caused this, it could have been because the alien plants had altered the nature of the soil, making it less suitable for fynbos seeds to grow. “But identifying one driver of change doesn’t preclude the existence of others. What about climate change?” Slingsby wondered. The researchers looked at weather records that showed that temperatures at Cape Point had increased by more than one degree Celcius since the 1960s. They also looked at the records of fires in the study area. Fynbos depends on fire for regeneration, and without fire, fynbos would eventually disappear. In the cool wet winter after a fire, fynbos regenerates; some burned plants re-sprout and the seedlings of other species pop up. Ecologists have long known that if the first summer after a fire is hot and dry, many of the new seedlings and resprouting plants will die, which will affect the species composition of the area. Natural weather variability means that after a fire there will be some hot summers, others not so hot. But climate change is changing that. “Unfortunately, the weather record for this study site shows that the duration of hot, dry summer weather has been increasing since the 1960s, suggesting post-fire mortality of plants should be more severe. Different study plots burned at different times and when we compared the plots, those that experienced more extreme weather in the first summer after a fire, showed a significant decline in species diversity. This confirms an impact of changing climate,” Slingsby said. The study also found that fynbos species that have a low tolerance of high temperatures have been disappearing, while those that have a higher tolerance of warmer temperatures have been moving in and colonising the study areas. CLIMATIC VARIABILITY Slingsby said climatic variability may provide years that were sufficiently benign to allow fynbos to regenerate after fire. “But many species that regenerate in the first year after a fire – most species in our study – are subject to a form of climatic Russian roulette. Unfortunately, as climate change intensifies, there are fewer empty chambers in the gun,” he said. “All indications are that the winners from climate change in the Cape are the invasive species like pines, eucalyptus and wattles. These invasive alien plants use more water than the indigenous vegetation and greatly up the game in terms of scale and impact of fires,” Slingsby said. Nicky Allsopp, SAEON’s Fynbos Node Manager, said a concern was that if there was more “drastic” climate change, then after each fire there would be poorer communities of plants, which may mean poorer ground cover. Less ground cover was likely to mean more soil erosion and might also affect the ability of rainwater to infiltrate the soil. Plants slow the movement of rainwater runoff, giving it more time to seep into the ground, recharging aquifers and seeping into streams and rivers over time. The researchers conducted their study in the Cape of Good Hope section of Table Mountain National Park, one of the most botanically diverse regions in the world. SAEON scientists and researchers from three South African universities and four institutions in the US collaborated in the study. The study was published in the Proceedings of the National Academy of Sciences.
Veitch J.A.,South African Environmental Observation Network |
Penven P.,CNRS Physics Laboratory
Journal of Geophysical Research: Oceans | Year: 2017
A modeling approach is used to investigate the influence of the Agulhas on the southern Benguela system. Two climatological ROMS simulations are run that are identical except that in one of them the effect of the Agulhas is removed. Comparing their outputs allows for a clear indication of the role of the Agulhas on both the large-scale and shelf dynamics. About 15 Sv of the mean transport of the Benguela Current is shown to be contributed by Agulhas influx, with the most intense flow being associated with extreme turbulence and its meandering nature is a reflection of the passage of Agulhas Rings. The injection of warm water is particularly evident beyond the shelf-edge, producing a perennially intense cross-shelf density front that is enhanced during upwelling season. This gradient drives a jet that is fastest at the shelf-edge but that extends from the midshelf to at least 100 km beyond it and is associated with dynamic uplift via vortex squashing. Similarly generated is the Good Hope Jet that extends northwestward from the western Agulhas Bank. Turbulence associated with Agulhas leakage increases rapidly beyond the shelf-edge causing the upwelling front in the southern Benguela to be subject to intense mixing, leaving a relatively uniform front there. Locally generated regions of high turbulence exist in the vicinity of the shelf-edge jets as well as further north in association with the large filaments that originate from the perennial Lüderitz upwelling cell, with or without the influence of the Agulhas. © 2017. American Geophysical Union.
Owen-Smith N.,University of Witwatersrand |
Goodall V.,South African Environmental Observation Network
Journal of Zoology | Year: 2014
Daily activity schedules and time budgets reveal how animals cope with changing environmental conditions in securing food and evading enemies. Theory suggests that animals in populations limited by food availability should be energy maximizers in their foraging time allocation, while those regulated by predation should minimize their mobile activity levels. We compared daily and seasonal variation in activity states among three species of grazing ungulates coexisting in the same region of Kruger National Park, South Africa, and for one of these species between regions differing in rainfall. These grazers differed in body size and digestive physiology, potentially affecting their activity patterns. Hourly movement rates recorded by GPS telemetry were partitioned among activity states by applying independent mixture models. All three species showed activity peaks during the early morning and late afternoon, while resting prevailed pre-dawn as well as through midday. African buffalo showed the strongest diel variation in activity and greatest depression of midday activity, consistent with their large body size. Buffalo maintained similar levels of activity through the day and night, while zebra and sable antelope showed higher levels of diurnal than nocturnal activity. During the late dry season, zebra and coexisting sable, but not buffalo, showed elevated foraging and total mobile activity. Zebra devoted more time to foraging than both ruminants, consistent with greater food intake requirements for hindgut digestion. Sable antelope inhabiting the region with higher rainfall showed similar activity levels to the sable herd in the drier area, but slower rates of movement while foraging and travelling and less elevation in foraging time towards the end of the dry season. Observed patterns indicated subtly changing interplay among different constraints bearing on activity patterns over the diel and seasonal cycles, especially those related to digestive physiology. Simplistic concepts of energy maximization or time minimization were not supported. © 2014 The Zoological Society of London.
Hempson G.P.,University of Cape Town |
Hempson G.P.,University of Witwatersrand |
Archibald S.,University of Witwatersrand |
Bond W.J.,University of Cape Town |
Bond W.J.,South African Environmental Observation Network
Science | Year: 2015
Megafaunal extinctions and a lack of suitable remote sensing technology impede our understanding of both the ecological legacy and current impacts of large mammal herbivores in the Earth system. To address this, we reconstructed the form and intensity of herbivory pressure across sub-Saharan Africa ∼1000 years ago. Specifically, we modeled and mapped species-level biomass for 92 large mammal herbivores using census data, species distributions, and environmental covariates. Trait-based classifications of these species into herbivore functional types, and analyses of their biomass surfaces, reveal four ecologically distinct continental-scale herbivory regimes, characterized by internally similar forms and intensities of herbivory pressure. Associations between herbivory regimes, fire prevalence, soil nutrient status, and rainfall provide important insights into African ecology and pave the way for integrating herbivores into global-scale studies.
Bond W.,South African Environmental Observation Network |
Bond W.,University of South Africa |
Zaloumis N.P.,University of South Africa
Philosophical Transactions of the Royal Society B: Biological Sciences | Year: 2016
Africa has the most extensive C4 grassy biomes of any continent. They are highly flammable accounting for greater than 70% of the world’s burnt area. Much of Africa’s savannas and grasslands occur in climates warm enough and wet enough to support closed forests. The combination of open grassy systems and the frequent fires they support have long been interpreted as anthropogenic artefacts caused by humans igniting frequent fires. True grasslands, it was believed, would be restricted to climates too dry or too cold to support closed woody vegetation. The idea that higher-rainfall savannas are anthropogenic and that fires are of human origin has led to initiatives to ‘reforest’ Africa’s open grassy systems paid for by carbon credits under the assumption that the net effect of converting these system to forests would sequester carbon, reduce greenhouse gases and mitigate global warming. This paper reviews evidence for the antiquity of African grassy ecosystems and for the fires that they sustain. Africa’s grassy biomes and the fires that maintain them are ancient and there is no support for the idea that humans caused large-scale deforestation. Indicators of old-growth grasslands are described. These can help distinguish secondary grasslands suitable for reforestation from ancient grasslands that should not be afforested. © 2016 The Author(s) Published by the Royal Society. All rights reserved.
Bond W.J.,South African Environmental Observation Network
Frontiers in Plant Science | Year: 2015
Modern flammable ecosystems include tropical and subtropical savannas, steppe grasslands, boreal forests, and temperate sclerophyll shrublands. Despite the apparent fiery nature of much contemporary vegetation, terrestrial fossil evidence would suggest we live in a time of low fire activity relative to the deep past. The inertinite content of coal, fossil charcoal, is strikingly low from the Eocene to the Pleistocene and no charcoalified mesofossils have been reported for the Cenozoic. Marine cores have been analyzed for charcoal in the North Pacific, the north and south Atlantic off Africa, and the south China sea. These tell a different story with the oldest records indicating low levels of fire activity from the Eocene but a surge of fire from the late Miocene (~7 Ma). Phylogenetic studies of woody plants adapted to frequent savanna fires show them beginning to appear from the Late Miocene with peak origins in the late Pliocene in both South American and African lineages. Phylogenetic studies indicate ancient origins (60 Ma+) for clades characteristic of flammable sclerophyll vegetation from Australia and the Cape region of South Africa. However, as for savannas, there was a surge of speciation from the Late Miocene associated with the retreat of closed fire-intolerant forests. The wide geographic spread of increased fire activity in the last few million years suggests a global cause. However, none of the potential global factors (oxygen, rainfall seasonality, CO2, novel flammable growth forms) provides an adequate explanation as yet. The global patterns and processes of fire and flammable vegetation in the Cenozoic, especially since the Late Miocene, deserve much more attention to better understand fire in the earth system. © 2015 Bond.
Kerwath S.E.,Forestry and Fisheries |
Kerwath S.E.,University of Cape Town |
Winker H.,University of Cape Town |
Gotz A.,South African Environmental Observation Network |
Attwood C.G.,University of Cape Town
Nature Communications | Year: 2013
Potential fishery benefits of Marine Protected Areas (MPAs) are widely acknowledged, yet seldom demonstrated, as fishery data series that straddle MPA establishment are seldom available. Here we postulate, based on a 15-year time series of nation-wide, spatially referenced catch and effort data, that the establishment of the Goukamma MPA (18 km alongshore; 40 km 2) benefited the adjacent fishery for roman (Chrysoblephus laticeps), a South African endemic seabream. Roman-directed catch-per-unit-effort (CPUE) in the vicinity of the new MPA immediately increased, contradicting trends across this species' distribution. The increase continued after 5 years, the time lag expected for larval export, effectively doubling the pre-MPA CPUE after 10 years. We find no indication that establishing the MPA caused a systematic drop in total catch or increased travel distances for the fleet. Our results provide rare empirical evidence of rapidly increasing catch rates after MPA implementation without measurable disadvantages for fishers. © 2013 Macmillan Publishers Limited.
Allsopp N.,South African Environmental Observation Network
African Journal of Range and Forage Science | Year: 2013
Many of the intransigent problems facing the world arise in complex systems. In this paper, I propose that communal rangelands in South Africa be recognised as complex social-ecological systems and that one of the reasons that development initiatives have had little impact on improving livelihoods and rangeland condition is that interventions have been based on reductionist thinking that has failed to recognise non-linearities and uncertainties in the system. This complexity resides in ecological, social and economic components of the system, and is characterised by dynamics operating at different scales within and beyond the boundaries of the rangelands. People and the environment are vulnerable to change in these systems from factors such as changing climate, economics, governance arrangements, as well as disasters. Policy that promotes adaptability and resilience, and is itself responsive to changing dynamics, should be sought. Complex systems modelling with an inclusive group of stakeholders holds potential for realising such policy. © 2013 Copyright NISC (Pty) Ltd.
Bernard A.T.F.,Rhodes University |
Bernard A.T.F.,South African Environmental Observation Network |
Gotz A.,South African Environmental Observation Network
Marine Ecology Progress Series | Year: 2012
Baited remote underwater video (BRUV) has been identified in the literature as a powerful long-term monitoring tool for subtidal rocky reef fish communities. To test this, a repeated-measures field experiment comparing unbaited remote underwater video (RUV) with BRUV was conducted in the Tsitsikamma National Park Marine Protected Area between June 2008 and February 2010. The results demonstrate that BRUV was more efficient at surveying the entire fish community, specifically invertebrate carnivores, generalist carnivores and cartilaginous species. On the other hand, RUV was more effective at surveying microinvertebrate carnivores. High variability in the RUV data resulted in the method requiring a greater number of samples to achieve the same diagnostic power as BRUV. However, RUV required a shorter deployment and post-sampling video analysis time, making it more time efficient. Baited remote underwater video was more sensitive in the detection of differences in abundance between habitat types, while the RUV data were more prone to an intra-species methodological bias linked to the percentage of reef visible in the frame of view. The scale of the response to the presence of bait was inconsistent among species, indicating that behaviour determined the area surveyed within the bait plume of BRUV. The benefits gained by sampling the fish community with RUV do not outweigh those obtained by altering the community through the presence of bait. However, in combination, the 2 methods are highly effective at monitoring the subtidal fish communities in the Agulhas bioregion of South Africa. © Inter-Research 2012.
O'Connor T.G.,South African Environmental Observation Network |
Puttick J.R.,University of Cape Town |
Hoffman M.T.,University of Cape Town
African Journal of Range and Forage Science | Year: 2014
Bush encroachment has been recognised in southern Africa since the late nineteenth century. Our review of 23 studies showed that the rate of woody cover change has ranged from -0.131 to 1.275% y-1. Encroachment was most rapid on small protected areas, intermediate under commercial tenure, and slowest under communal tenure and large, natural environments with mega-herbivores present. Several drivers of bush encroachment, which interact and change over time, have been proposed. Fires, for example, were actively suppressed during the early twentieth century. However, rainfall interacts with fire and the rate of woody increase under fire exclusion is linearly related to mean annual rainfall. A reduction in browsing herbivores from the nineteenth century would have had a positive cumulative effect on woody cover whilst an increase in grazing herbivores would have reduced the competitive effect of grasses. Encroachment was most rapid during the high rainfall, mid-1970s, which followed the 1960s drought when cattle numbers were at their peak, and the grass layer was degraded. Increasing atmospheric [CO2] and climate change have emerged as important drivers in the recent literature. Bush encroachment depends on the interplay of history, environment, management and vegetation, recognition of which is essential for containing encroachment. © 2014 NISC (Pty) Ltd.