Conclusions

In many parts of the world, especially those long settled by societies with agricultural or urban components, an evaluation of present-day ecosystems and future sustainability should recognize the importance of past human activities and the roles they have played in creating and modifying the environmental systems upon which sustainability depends.

Many of the environmental impacts of past human activities are mediated through changes in land-use/cover. These impacts include feedbacks into the climate system, both directly and via changes in atmospheric greenhouse gas concentrations. Land-cover changes arising from human exploitation are also often implicated in changes in hydrologic and erosional regimes: they alter the canvas upon which the interplay between climatic and hydrologic variability is expressed. They are also central to the creation, maintenance or destruction of habitats upon which biodiversity depends.

Many past human societies have been strongly affected by climate change and it is unrealistic to explore the long-term fate of past cultures and civilizations without acknowledging this. That said, acknowledging the role played by climate change should not lead to interpretations of cultural expansion or demise in terms of a simple causative link between climate and the fate of societies. The nature of social organization, its flexibility, and adaptive capacity are critical in determining the success or otherwise of human responses to any external stresses.

From the above, it would seem important to use the record of past humanenvironment interactions, in all its complexity, as part of the basis for planning a sustainable future in the face of projected climate change, with all its daunting implications. For as long as a methodological divide exists between researchers dealing with contemporary and future change and paleoscientists concerned with longer time perspectives, the desired synergy between the two types of study will never be fully realized. The divide springs in part from training and the consequent differences in the methodological repertoire acquired, and in part from the extent to which much of paleoscience is seen as "history" rather than part of a temporal continuum. The climate community has succeeded in bridging the gap between paleoresearch and future projections by viewing reconstructions of past climatic variability as insights into the nature of processes, rather than simply as retrospective snapshots of "history". From this springs recognition of the value of reconstructions of past variability and change on a wide range of time-scales. Let this serve as a model for the wider research community that embraces human as well as biophysical aspects of environmental change.

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