Indicators of regime shifts in long-term ecological data

Background/Question/Methods

Long-term ecological data provide opportunities to examine and compare ecosystem-specific indicators of regime shifts.  Our objective was to compare regime shifts from a number of different ecosystem types to determine similarities and differences in indicators. We used long-term data (> 10 years) in the EcoTrends project (http://www.ecotrends.info) from the US Long Term Ecological Research network of sites and from other state and federal agencies in this comparative analysis. Data included both plants and animals from terrestrial, aquatic, marine, and polar systems.

Results/Conclusions

In general, similar dynamics were observed across all systems in that abrupt increases in one system component were concurrent with abrupt decreases in another component. Length of time for the regime shift to occur varied across systems. In many cases, interactions among abiotic and biotic processes were important in driving these dynamics, and feedback mechanisms were important in maintaining the new regimes. In some cases, climatic drivers pushed a system past a threshold that provided opportunities for a regime shift, either by a shift in species dominance or by the successful invasion of a new species. This retrospective analysis can be used as a critical step in identifying key processes and conditions for which regime shifts occurred in the past, and to determine the potential for regime shift reversals. However, future analyses of indicators will also need to account for changing climatic conditions and other drivers, including invasive species, which were not part of the historic regime shift.