Overgrazing:
Environmental Assessment: Pressure State Response Indicators
 
Pressure State Response Indicators need to be looked at in linked sets. They link physical indicators of change with socio-economic indicators of pressure and political/institutional indicators of response.

Pressure
Why is it happening? Is there overgrazing? If so, what has caused it?

Increase in Animal Numbers - has there been a change in animal numbers or the type of stock held. Census data may (or may not) be freely available. However figures may have to be updated with a field survey combined with local consultation with herders. In some cases aerial counts may be available, or may be carried out to establish present stocking densities. The complexity of the survey work will depend on the availability of existing and historic data.

Artificially Increased Grazing Pressure - Poorly placed resources such as watering points can result in overgrazing of some areas and the under-utilisation of others.

Reduction in Mobility - a change in the freedom of movement of livestock is often an underlying cause of overgrazing. Historic records may be compared with present information on herd and herder mobility. Consultation with stakeholders will provide good information.

Reduction in Communal Grazing or Reduction in Available Area - often linked to the conversion of the better range areas to arable production in response to increasing human populations and/or to an increased need for cash crops. Information may be available through the same remote sensing data sets as used for vegetation cover. Additional information may be available on land registration from land authorities. And again consultation will be an essential part of the process of establishing the extent of the problem.

Shift in Herd Composition - e.g. cattle to small-stock, will inevitably change the nature of the grazing / browsing pressure.

Additional Contributory Reasons: To what extent is increase in human population numbers a contributory factor leading to overgrazing? Are there any political or institutional reasons for overgrazing to have taken place? For example, have subsidies resulted in any market changes? Has a general deterioration (or increase) in the quality of transportation facilities resulted in a changed market for livestock products?

State  (What is happening? For example, is there an indication of a major increase in erosion?) Changes in Vegetation Cover - This can be assessed from a time series of low resolution satellite images using a change in the vegetation index to indicate a change in biomass. The information is widely available and whilst it may be considered as relatively costly, these costs are coming down with the advent of new remote sensing platforms and pricing policies. However, the analysis will have to be carried out by an agency with experience of this technology.

Change in Species Composition and Abundance - invasion of weed species and loss or reduction of key or important indigenous species. This may be recognised by local herders and/or botanists from a local institution. The analysis is likely to be highly subjective unless previous survey work on species composition and distribution (using the same analytical techniques) is available. This analysis is relatively low cost and can be combined with discussions with herders and other stakeholders on pressure / state indicators as long as an interdisciplinary team can be put together for the fieldwork. The use of fixed point photography  can contribute to a monitoring programme over a number of years. Similarly, there may be a change in the abundance, distribution and species composition of wildlife.

Change in Rangeland Quality - Simple techniques of classification can rapidly build up into an overall assessment of rangeland condition without the need for extensive and time consuming collection of large amounts of specialist data. An example of assessment of range condition for horses in Iceland serves to illustrate the potential of these methods.

Change in Climate - This may have an effect on rangeland productivity independent of human induced pressures. Changes in conditions during the growing season may be indicated by time series of climate data, which are generally readily available,. Examination of a time series data set should indicate whether a change in weather patterns is a potential contributing factor to land degradation. Time series of satellite data may also provide evidence for change, especially NOAA AVHRR imagery processed to provide a vegetation index (e.g. NDVI). However, the most important use of these data sources will be to emphasise and to quantify the normal annual and seasonal climatic variation, i.e. the variability from year to year.

Indications of Accelerated Erosion - field surveys can establish that accelerated erosion is taking place through the identification of key erosion features such as root pedestals. Again this is subjective unless it can be compared to previous survey work, but still has the advantage of allowing discussion with herders and other stakeholders. Additional data on sediment load in stream may also be available from hydrological institutions, indicating changes in erosion. And again the assessment should not be a major cost.

The outcome of the analysis will be an answer as to whether overgrazing is actually taking place, which stakeholders are involved in the process, probable causes of overgrazing and will point to possible options to alleviate the situation. Response Policy Changes - a review of policy will indicate whether there has been a policy of encouraging arable expansion into range areas, or a privatisation of some communal areas. Other policy changes may relate sedentarisation of pastoralist groups for social development reasons or as a result of insecurity, famine / drought, or cultural changes.

Uneven grazing distributions can, where practical, be reduced by changing paddock shape, or through fenceline relocation (including complete removal and the addition of new fences), paddock sub-division or by the addition, relocation or closing of watering points. Models of animal distribution can assist in the application of these decisions once they are validated for the particular environment in which they are applied.
 

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