Healing the planet: Conservation of the world`s tropical forests
Graham, Alan .
Time and Past Ecosystem Dynamics in Fashioning Views on Conserving Extant Neotropical Forest.
In the Cretaceous there were eight New World terrestrial Ecosystems that were distinct or only shadowy versions of those present today. Now, 65 Ma later, there are 12 that constitute the EarthÃ¢€™s living envelope. Knowledge of the intervening history is useful for conservation in several regards. It provides analogs for conditions anticipated in the near-future and estimations of the biotic response. Atmospheric CO2 was ca. 300ppm just before the Industrial Revolution, it is 380 ppm today, it is expected to rise to 550 ppm by mid-century, and to 1000 ppm by the end of the century. CO2 concentration was ca. 2000 ppm in the early Eocene (ca. 45 Ma), it dropped to less than 200 in the late Pliocene (ca. 2.6 Ma) and, therefore, bracketed the values predicted for modern times. History provides a basis for assessing stability of tropical ecosystems. Conventional wisdom through about the 1970s was that rain forests and rain-forest environments were stable through long periods of geologic time with the implication that they could be impacted with impunity and would always recover because they had always done so in the past. That view was replaced with a new paradigm based on the fossil record that tropical forests are an ephemeral, delicately balanced system that when altered take intervals measured in geologic time to recover. Now the former view is being resurrected for the lowland tropical rainforest even in light of multiple 4-5oC lowerings of mean annual temperature and significant drying during each cold interval of the Quaternary. The question needs to be better resolved. History further provides insights into the changing lineage composition of extant communities. Studies on Pleistocene(2.5 Ma to ca. 12,000 yrs) and Holocene vegetation (after 12,000 yrs to the Present) have demonstrated that with each comparatively slight change in climate, ecosystems are altered and usually do not recover to their same former composition. Thus, a modern view of conservation strategies incorporating the dynamics of history is that setting aside segments of the landscape is actually preserving fluctuating habitats or weigh stations through which biotas of varying composition will be passing at an ever quickening pace.
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1 - Missouri Botanical Garden, PO Box 299, St. Louis, MO, 63166, USA
Presentation Type: Symposium or Colloquium Presentation
Location: Maryland Room/Chase Park Plaza
Date: Wednesday, July 13th, 2011
Time: 8:15 AM