To discover the patterns of biodiversity, information on biodiversity has to be collected. This information usually takes the form of distributions of species. This information is collected in what are known as surveys. Exactly how a survey is carried out depends on the circumstances, and so the techniques used on surveys are only standardized at all for particular groups. There are, however, three major factors that determine how the survey will proceed.
The first factor is why the survey is to be carried out. Scientific studies, monitoring programs for endangered species and biological prospecting all have different aims, for instance. Scientific studies tend to examine every species, monitoring programs usually only want to look at specific species, and biological prospecting focuses on certain types of species that hold promise.
What is to be measured is the second factor. The level of biodiversity that is being examined will have a definite effect on how the survey will be carried out. Species are the most common measurement, but genetic diversity can also be measured by taking samples and analyzing them in the laboratory afterwards. With groups such as insects, it is often difficult and laborious to identify every individual to species. In these sorts of cases it is common to identify them to some higher classification level, such as family. When proper measurements of diversity are not possible, surrogate measurements may be used, such as the amount of energy available to the system. These tend to roughly indicate the number of species that would most likely be found in an area, but cannot determine the particular species that are found there. Despite this they may be the only practical way to estimate diversity when more detailed surveys are not possible.
Finally, the particular techniques that can be used will be shaped by the conditions of the survey. Ideally, every survey would be completely standardized, allowing different surveys to be easily compared to one another, but this is often impossible for practical reasons such as time and funding. Different surveys are instead standardized as much as is possible. The typical survey is done in a grid comprised of squares. Size of each square is important, as scale has been shown to have a large effect on diversity surveys. The amount of effort that goes into identifying species in each quadrat (square) should be the same.
For more information on biodiversity surveys, see the survey section in the Redpath Museum's Quebec Biodiversity Website.