Showing papers by "Barend F.N. Erasmus published in 2014"

Reviewing Biosphere Reserves globally: effective conservation action or bureaucratic label?

Abstract: The Biosphere Reserve (BR) model of UNESCO's Man and the Biosphere Programme reflects a shift towards more accountable conservation. Biosphere Reserves attempt to reconcile environmental protection with sustainable development; they explicitly acknowledge humans, and human interests in the conservation landscape while still maintaining the ecological values of existing protected areas. Conceptually, this model is attractive, with 610 sites currently designated globally. Yet the practical reality of implementing dual 'conservation' and 'development' goals is challenging, with few examples successfully conforming to the model's full criteria. Here, we review the history of Biosphere Reserves from first inception in 1974 to the current status quo, and examine the suitability of the designation as an effective conservation model. We track the spatial expansion of Biosphere Reserves globally, assessing the influence of the Statutory Framework of the World Network of Biosphere Reserves and Seville strategy in 1995, when the BR concept refocused its core objectives on sustainable development. We use a comprehensive range of case studies to discuss conformity to the Programme, the social and ecological consequences associated with implementation of the designation, and challenges in aligning conservation and development. Given that the 'Biosphere Reserve' label is a relatively unknown designation in the public arena, this review also provides details on popularising the Biosphere Reserve brand, as well as prospects for further research, currently unexploited, but implicit in the designation.

Rural Outmigration, Natural Capital, and Livelihoods in South Africa.

Abstract: Rural households across the globe engage in both migration and natural resource use as components of livelihood strategies designed to meet household needs. Yet, migration scholars have only recently begun to regularly integrate environmental factors into empirical modelling efforts. To examine the migration-environment association in rural South Africa, we use vegetation measures derived from satellite imagery combined with detailed demographic data from over 9000 households at the Agincourt Health and Demographic Surveillance Site. Results reveal that household-level temporary migration is associated with higher levels of local natural capital, although no such association exists for permanent migration. Further, more advantaged households exhibit a stronger association between migration-environment, in-line with the 'environmental capital' hypothesis, suggesting that natural resource availability can facilitate household income diversification. We argue that a focus on migration's environmental aspects is especially timely in the contemporary era of climate change and that natural capital availability and variability represent critical pieces of the empirical migration puzzle, especially regarding cyclical livelihood migration.

Investigating potential determinants of the distribution limits of a savanna woody plant: Colophospermum mopane

Abstract: Questions Early bioclimatic models predict that climate change in southern African savannas will cause a huge southward and westward range shift of the savanna tree Colophospermum mopane (Kirk ex Benth.) Kirk ex J.Leon. C. mopane is an economically and ecologically important subtropical savanna tree that forms mono-dominant stands across 30% of southern African savannas. We investigate the validity of these initial range expansion predictions to answer the following questions: what are the regional-scale drivers of the distribution of C. mopane in southern African savannas; and what are the landscape-scale distribution patterns of this species? Location Central Lowveld, Kruger National Park, South Africa. Methods We investigate the validity of very early range expansion modelling predictions using a regional-scale, climate envelope niche model, and fine-scale field mapping of the current boundary, to understand which environmental variables may determine the distribution limit of this signature species. Results Our findings indicate that both non-climatic (dry season day length) and climatic (minimum temperatures) variables limit the regional distribution of C. mopane. At the landscape scale, the distribution of this species is restricted to the warmer parts of the landscape, suggesting minimum temperature appears to be the primary factor determining its landscape-scale distribution. Conclusions This study provides the first detailed model of environmental factors that may limit the regional distribution of C. mopane, and allows us to formulate testable hypotheses regarding the determinants of the range of a keystone species.

Extracting Structural Vegetation Components From Small-Footprint Waveform Lidar for Biomass Estimation in Savanna Ecosystems

Abstract: Measurement of vegetation biomass accumulation is critical for ecosystem assessment and monitoring, but doing so typically involves extensive field data collection that yields relatively crude structural outputs, e.g., plot- or site-level metrics. This study assessed the utility of airborne light detection and ranging (lidar) waveform features to explain structural and biomass variation in a savanna ecosystem across a land-use gradient. The ability of aboveground waveform lidar features to model field-based woody and herbaceous biomass measurements was evaluated statistically by regression models using forward variable selection. Waveform features explained 76% of the variation in woody biomass in a regulated communal land use area (RMSE = 29.0 kg). The waveform features were also correlated to herbaceous measurements in the same land-use area, with increased correlations at higher biomass levels. These results indicate that small-footprint waveform lidar data potentially can be used as a single modality to describe heterogeneous woody cover in a savanna environment; however, further research is warranted during the full growing season to fully evaluate its performance.

Hyperspectral reflectance features of water hyacinth growing under feeding stresses of Neochetina spp. and different heavy metal pollutants

Abstract: Spectral signatures of water hyacinth grown with biocontrol agents Neochetina eichornia and N. bruchi and various heavy metal pollutants were collected at the plant canopy level using a hand-held spectrometer to detect the biocontrol agent and heavy metal-induced plant stresses and the interaction between the two stressors. Water hyacinth was grown in 65l tubs, each with a single element from one of: As 1 mg l−1, Au 1 mg l−1, Cu 2 mg l−1, Fe 0.5, 2 and 4 mg l−1, Hg 1 mg l−1, Mn 0.5, 2, and 4 mg l−1, U 1 mg l−1, and Zn 4 mg l−1, with the exception of the control treatment. Three weeks after the metal treatments, the weevils were added to each tub, including those of the control treatment. Spectral measurements were taken before and after the addition of the weevils. Several spectral indicators of plant stress including red edge normalized difference vegetation index RE-NDVI, modified red edge NDVI mNDVI705, modified simple ratio mSR, photochemical reflectance index PRI, and red edge position REP calculated using first derivative and linear extrapolation and water band index WBI were used to identify the plant stresses of water hyacinth. The spectral indicators of both metal and weevil plant stressors were correlated with the leaf chlorophyll content from the SPAD-502 readings at the end of the experiment. Correlations of mNDVI705 with SPAD-502 readings were the highest followed by the indicators of REP. Cu-, Hg-, and Zn-treated plants showed significantly lower chlorophyll contents compared with the control treatment. A similar trend with four additional treatments As, Fe-M, Mn-L, and Mn-H was seen after the release of the weevils, indicating plant stress due to feeding by the biocontrol agent. However, adult and larval feeding was significantly reduced by Cu, Hg, and Zn elements, of which Cu was the most stressful. These results indicate that hyperspectral remote sensing has potential as a tool to determine the health status of water hyacinth from a remote location, to inform management interventions in control of the weed. However, its usage at a larger scale requires further studies.

Savanna woody vegetation classification – now in 3-D

Abstract: Copyright: 2013 Wiley Online Library. This is an ABSTRACT ONLY. The definitive version is published in Applied Vegetation Science, pp 1-13, doi: 10.1111/avsc.12048

Digestive efficiencies are independent of gut passage times in rainbow skinks (Trachylepis margaritifer).

Abstract: Constraints on physiological processes imposed on ectotherms by environmental temperatures can be severe, affecting many aspects of their biology. Included in the suite of physiological processes affected is gut motility, with below optimum temperatures generally resulting in slow gut passage. Trachylepis margaritifer (rainbow skink) however presents an unusual pattern whereby gut passage time decreases at a low temperature compared to when at an intermediate temperature. It has been suggested that this may be a ‘cutting-your-losses’ response whereby nutritional gain is sacrificed by voiding the digesta to reduce the risk of these rotting within the gut at these low temperatures, and if this is so, it should result in reduced digestive performance at 25 °C. We tested this hypothesis by measuring appetite, apparent digestive efficiency (ADE) and apparent assimilation efficiency (AAE) in T. margaritifer . We found that although temperature significantly affected appetite and gut passage time, it did not affect digestive efficiency. Both ADE (> 90%) and AAE (> 80%) were high and temperature-independent across the range tested. Thus, the ‘cutting-your-losses’ hypothesis does not explain faster gut passage at 25 °C. High digestive parameters could be maintained by increasing concentrations of digestive enzyme at low temperatures but remains to be tested in this species.