Introduction

Why measure environmental variables?

When describing the distribution and abundance of plants and animals it is important to describe abiotic features of the environment for two reasons. First, presentation of this information is of enormous help to your audience trying to picture the environmental context in which the biological census work was carried out. In other words, it provides the backdrop. Secondly, and more importantly, the physical and chemical variables you measure are often key explanatory variables for the biological phenomena you observe. In other words, they may well be the drivers of the spatial and temporal patterns you record in a census. Subsequent management of your target species or communities will often require controlling and manipulating these drivers, whether they be phosphate levels in a lake or shade on a woodland floor.

How do I know which variables to measure?

The answer to this question may be easy if other researchers have done similar work already, but in many censuses and surveys it might not be possible to tie down key variables in advance. In that case, you might be tempted to measure everything you can, just in case you overlook something. However, ‘Sutherland's Deadly Census Sins’ (Chapter 12) apply equally well to environmental variables: it is all too easy to expend inappropriate time and effort in measuring the wrong variable. First, don't just do what everyone else has done – they may be entirely wrong and slavishly following their example will only compound the problem.