Fire, ice, and invasion

The November 2007 Special Issue of Frontiers in Ecology and the Environment focuses on paleoecology, which uses fossilized remains and soil and sediment cores to reconstruct past ecosystems.

Some scientists argue that the pre-Columbian Amazon was pristine, with indigenous people living in harmony with nature. Others suggest that the Amazon is a “manufactured” landscape, altered by and disturbed by human activities even before the arrival of Europeans. In “Amazonian exploitation revisited: ecological asymmetry and the policy pendulum,” Mark Bush (Florida Institute of Technology) and Miles Silman (Wake Forest University) discuss this debate.

Bush and Silman present paleodata from fossil pollen and charcoal in soil cores that support both perspectives. They argue that in some areas of the Amazon, human impact was extreme, especially on bluffs around rivers. Yet they also found vast stretches of the forest where human influence was minimal. If widespread disturbance was typical in the Amazon forest until just 500 years ago, that suggests the ecosystem is resilient to human activities, including logging. However, as the authors demonstrate, the “manufactured” landscape argument only holds true for localized patches of forest, and should not be used as a basis for management of the Amazon as a whole.

Heading north, the next paper addresses the use of lakes and ponds for reconstructing environmental changes in the Arctic. John Smol (Queens University, Ontario) and Marianne Douglas (University of Alberta, Edmonton) summarize some of the recent lake sediment studies in “From controversy to consensus: making the case for recent climate change in the Arctic using lake sediments.” Scientists working in these regions have noted recent changes in the abundance of a group of pythoplankton known as diatoms, as well as changes in other plankton. The researchers found striking and often unprecedented changes in post-1850 sediments, which could be linked to ecological shifts consistent with global warming. Further changes are predicted to be greatly amplified in the polar regions, putting the ecological integrity of these sensitive ecosystems at risk.

In another paper, “Paleoecology and ‘inter-situ’ restoration on Kauai, Hawaii,” David Burney (National Tropical Botanical Garden, Hawaii) and Lida Pigott Burney (Makauwahi Cave Reserve, Kalaheo) examine human-caused extinctions on the Hawaiian island of Kauai. Paleoecological studies from around the world show the devastating effects of human colonization on islands. Island histories reveal that hunting and landscape changes caused by humans each play a key role, but many of the extinctions seen on islands are probably from introduced predators, herbivores, plants, and diseases. On the island of Kauai, conventional conservation tactics focus on both restoring organisms in the wild as well as using zoos, botanical gardens and genetic banks. However, these tactics aren’t working well. The authors propose that conservationists try inter-situ conservation – the establishment of species by reintroduction to locations outside the current range but within the recent past range of the species. This method could provide a hedge against extinction.

Another paper in the Special Issue, “Paleoecology and ecosystem restoration: case studies from Chesapeake Bay and the Florida Everglades,” by Debra Willard and Thomas Cronin (US Geological Survey), focused on using paleoecology as a restoration tool. John Williams (University of Wisconsin, Madison) and Steve Jackson (University of Wyoming, Laramie) created a simulation of future climates and ecological responses based on the Intergovernmental Panel on Climate Change’s emission scenarios in the year 2100 in their paper, “Novel climates, no-analog communities, and ecological surprises.” Daniel Gavin (University of Oregon, Eugene) and colleagues looked at charcoal records from lake sediments and soil profiles in “Forest fire and climate change in western North America: insights from sediment charcoal records.” Their study focuses on historic forest fire ranges to better understand the vulnerability of all habitats to fire.