Earlier this year, I happened to come across a very interesting TED talk given by Allan Savory, the man behind modern holistic management and planned grazing. In it he outlines his experience and research into the drivers of worldwide grassland desertification and the climate change associated with this, stating that the problem is not only caused by over-grazing, but also by removing grazing animals from those environments. He explains that perennial grasses require a large, moving herd to flatten and fertilise them in order to quickly regenerate, otherwise they mostly decay slowly and die. This eventually results in too much soil exposure and water evaporation, as well as the release of carbon stores from the dead plant material and soil. Not an easy process to recover from…or is it?
Through his holistic management techniques, Savory has shown many examples of reversing desertification by using livestock and wildlife for planned grazing that mimics natural herds and their important role in the grassland cycle. This approach is based on managing the ecological, social and economic factors of an environment together.
The idea that there is a way to sustain the growing demand for food as well as reduce atmospheric carbon dioxide levels AND improve biodiversity has definitely stayed with me through this semester, particularly during our fieldwork into restoration of modified ecosystems, adaptive management and agri-environmental schemes.
In terms of conservation planning, there are a few things to consider with this method:
1. The effects of grazing on different grass species
Even though many grassland species have evolved with grazers, some are ‘increasers’ that respond well to more grazing, while other ‘decreasers’ can be grazing-sensitive and will have lower densities. For example, Australian grasses respond more favourably to lighter grazing, typical of our marsupials, than to intensive livestock grazing (McIntyre et al., 2003).
2. Other species within the ecosystems
The level of grazing intensity also has an impact on the composition of other species, such as pollinators. A study by Sjodin et al. (2008) suggests that bees (Apoidea), butterflies (Lepidoptera), hoverflies (Syrphidae) and beetles (Coleoptera) have unique responses to variables at local and landscape scales, including vegetation height, the amount of grassland cover and water levels, which has implications for management regimes.
3. The context of the landscape
‘Man-made deserts’ occur in a variety of complex socio-economic contexts, so they will be managed differently depending on the particular goals of the stakeholders, such as a national park reserve plan vs that of agricultural land. Since many species are now endangered due to increased desertification and ecological disturbance (Ayyad, 2003), conserving biodiversity should be an important focus within the challenge of restoring any desertified landscape.
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Ayyad, M. A. 2003. Case studies in the conservation of biodiversity: degradation and threats. Journal of Arid Environments 54:165-182.
McIntyre, S., K. M. Heard, and T. G. Martin. 2003. The relative importance of cattle grazing in subtropical grasslands: does it reduce or enhance plant biodiversity? Journal of Applied Ecology 40:445-457.
Sjodin, N. E., J. Bengtsson, and B. Ekbom. 2008. The influence of grazing intensity and landscape composition on the diversity and abundance of flower-visiting insects. Journal of Applied Ecology 45:763-772.