Environmental Monitoring Time Scales: From Transient Events To Long-Term Trends

Abstract

Environmental studies and monitoring programs provide information that is required to make wise decisions regarding the present and the future state of resources. Too restricted a perspective on either temporal or spatial scales curtails the adequacy of the associated decisions. As environmental scientists, we have often over-sampled the one-week to five-year time scale and the 1 to 1000 km spatial scale, neglecting other time and spatial scales. Environmental studies seldom collect samples more frequently than once per week, and studies seldom exceed five years and very rarely exceed 25 years. Correspondingly, environmental studies usually focus upon repeated sampling at specific locations, usually many tens or hundreds of kilometers apart. However, many important environmental events take place on temporal and spatial scales outside this narrow focus. Understanding processes that take place outside this `time and space window’ is critical to making wise decisions. The scale at which processes operate may change; such changes may be more significant than minor changes in the mean level. In the environmental sense, all time scales and spatial scales that exist in ecosystems are relevant. Additionally, time scales at which we sample must be appropriate for the spatial scales of the phenomena with which we are concerned. This paper provides some examples of results from data gathered outside the usual temporal ‘window’ and highlights the relevance and complementary nature of such results to environmental issues. Inclusion of additional time scales is crucial to understanding environmental processes and fundamental to identification of the functioning of ecosystems.