Pressure-State-Response Indicators:
An Example for a Semi-Arid Grazing System

One of the risks associated with Semi-arid Grazing Systems is land degradation as a result of overgrazing. However there may be other factors involved or contributing to overgrazing such as climate change. In addition the root cause of overgrazing may be different, stock numbers may be increasing, there may be a loss of grazing area to arable farming, seasonal mobility may be restricted by political unrest or changes in access to water resources may be restricting movement.

A livestock planner may suspect that there is a problem of accelerated erosion resulting from overgrazing. And if there is overgrazing he needs to find out why it is happening.

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.

The following indicators may be appropriate for his situation

Pressure:

> Why is it happening?
> Is there overgrazing?
> and 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 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 histroic data.

Reduction in Mobility - a change in mobility 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 - often linked to the conversion of the better range areas to arable production. 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.

State

> What is happening?
> Is there an indication of a major increase in erosion?

Changes in Vegetation Cover - could 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 freely available, but the analysis will have to be carried out by an agency with experience of this technology.

Changes in Vegetation Species - invasion of weed species and loss of key species, may be recognised by local herders and/or botanists from a local institution. The analysis is more subjective unless previous surveywork on species distribution is available. But the analysis is relatively low cost and can be combined with other discussions with herders and other stakeholders on pressure indiactors.

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 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.

Climate Data - generally readily available, a look at a time series data set should indicate whether a change in weather patterns is a potential contributing factor to land degradation.

Response

> What is being done about it?
> Or in this case were there contributory political or institutional reasons for overgrazing to have taken place?

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.

The outcome of the analysis will be an answer as to whether overgrazing is taking place, which stakeholders are involved in the process, probable causes of overgrazing and will point to possible options to alleviate the situation.

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