ABSTRACT
Land degradation encompasses a vast array of biophysical and socio-economic processes, which make its assessment difficult to encapsulate in a few simple measures. It occurs over a variety of timescales – from a single storm to many decades. It happens over many spatial scales – from the site of impact of a single raindrop through to whole fields and catchments. Without extreme care, measurements undertaken at one set of scales cannot be compared with measurements at another. This is why this handbook:
• adopts a farmer-perspective and hence the type of assessments at field and farm level, and timescales that have significance for the farmer (though, of course, these also vary according to individual circumstances – for example, the impact of erosion on the current crop, or concerns for longterm sustainability);
• focuses on the concerns of land users – primarily the way that land degrada-
tion makes farming more difficult, and the impact of degradation on productivity;
• concentrates on relatively simple field indicators, some of which can be quantified into absolute rates of soil loss, but none of which should be taken in isolation. The indicators are ones that farmers have told us they notice, and therefore information on them is more readily available. The indicators are also readily discerned in the field, although they are more apparent at some times of year and in some environmental circumstances.
