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.
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.
Owen-Smith N.,University of Witwatersrand |
Goodall V.,University of Witwatersrand |
Goodall V.,South African Environmental Observation Network |
Fatti P.,University of Witwatersrand
Wildlife Research | Year: 2012
Context To interpret spatial utilisation distributions, there is a need to translate animal locations obtained from global positioning system (GPS) telemetry into the activities performed and, hence, benefits derived, from particular places and times of day. Derived activity patterns also reveal how animals cope in changing environmental conditions. Aim The aim of our research was to develop and test an objective, consistent and biologically faithful method for deriving activity states from movement rates between successive GPS locations. Methods The method entails fitting mixtures of component statistical distributions to the frequency distribution of hourly step displacements. Breakpoints indicating transitions between predominant movement modes were identified by fitting exponential segments. Breakpoints were incorporated as off-sets for gamma distributions, but not needed for log-normal distributions. This procedure was applied to movement data for three large grazing ungulates. Key results Models consistently distinguished four movement modes interpreted as representing resting, foraging, mixed movement and travelling activity. Breakpoints and parameter estimates were consistent among seasons and herds of each ungulate species. The exponential-segment model and both mixture models closely represented observed daily activity patterns. However, some adjustment of the derived time budgets was needed to be consistent with observations. Key conclusions Mixture models provide an objective, reliable and biologically meaningful procedure for assessing seasonal, annual and spatial variation in the activity patterns of large ungulates from GPS data. Implications The method can potentially be applied to other mobile foragers large enough to carry GPS collars. © 2012 CSIRO.
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.
Higgins S.I.,University of Otago |
Buitenwerf R.,Landcare Research |
Moncrieff G.R.,South African Environmental Observation Network
Global Change Biology | Year: 2016
Biomes are important constructs for organizing understanding of how the worlds' major terrestrial ecosystems differ from one another and for monitoring change in these ecosystems. Yet existing biome classification schemes have been criticized for being overly subjective and for explicitly or implicitly invoking climate. We propose a new biome map and classification scheme that uses information on (i) an index of vegetation productivity, (ii) whether the minimum of vegetation activity is in the driest or coldest part of the year, and (iii) vegetation height. Although biomes produced on the basis of this classification show a strong spatial coherence, they show little congruence with existing biome classification schemes. Our biome map provides an alternative classification scheme for comparing the biogeochemical rates of terrestrial ecosystems. We use this new biome classification scheme to analyse the patterns of biome change observed over recent decades. Overall, 13% to 14% of analysed pixels shifted in biome state over the 30-year study period. A wide range of biome transitions were observed. For example, biomes with tall vegetation and minimum vegetation activity in the cold season shifted to higher productivity biome states. Biomes with short vegetation and low seasonality shifted to seasonally moisture-limited biome states. Our findings and method provide a new source of data for rigorously monitoring global vegetation change, analysing drivers of vegetation change and for benchmarking models of terrestrial ecosystem function. © 2016 John Wiley & Sons Ltd.
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.