In addition, political boundaries produce organisational problems which frustrate the sampling designs of scientists. There has been considerable effort in developing environmental and management monitoring systems and databases. The majority of these are concerned with specific topics, e.g. pollution or crop production. ECN is a good example of such an integrated monitoring network which links biological variables with other physical and chemical measurements more commonly recorded in sectoral monitoring programmes. The lack of a concerted effort to monitor the terrestrial contribution to global change and its effects has stimulated a number of studies and proposals.
Much emphasis is placed on climate change.
However the importance of detecting changes in pollution and land use is generally accepted, partly because they are changing on a global scale, are affected by climate, but also because the impact of climate change cannot be detected without having information on pollution and land use. Three other programmes illustrate the emerging importance of site networks in global monitoring. Bruns et al. In contrast, the Biosphere Reserve network of about 300 sites world wide has a strong biological emphasis. The research programme of IGBP is relevant here, especially the programme on Global Change in Terrestrial Ecosystems.