The following article originally appeared in the 2002-2003 IES Biennial Report.
Ecosystem engineers are organisms that change the physical structure and chemistry of their environment. They play a major role in creating, modifying, maintaining, and destroying habitats that other species depend upon. As a consequence, they can profoundly affect the way ecosystems function. Ecosystem engineers can be plants, animals or microorganisms, and, depending on the magnitude of the environmental changes they cause, their effects on ecosystem processes and other species can be subtle or extreme. Examples include: dams built by beaver, shade cast by trees, increased soil drainage from earthworm burrowing, coral reefs protecting other species from powerful waves, and shelters made from the empty shells of dead mollusks. |
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| "Through their interactions with the environment, ecosystem engineers have the ability to create or destroy habitat for other plants and animals. By researching a range of engineers, from beaver to humans, we hope to distill how habitat modifiers impact ecosystem function."
IES ecologist Clive Jones |
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Countless organisms modify the environment, yet we know relatively little about the ecological consequences of ecosystem engineering. How do engineer modifications control energy and material flows? What are the consequences for species that live in these ecosystems? What determines whether engineering has large or small effects? How does engineering impact biodiversity? How can we understand the bewildering diversity of engineers and their effects? IES ecologist Dr. Clive Jones, a pioneer in ecosystem engineering research, is striving to answer such questions. He described the general process and developed the concepts, coining the term ecosystem engineering in a 1994 paper with colleagues Drs. John H. Lawton and Moshe Shachak. His findings are contributing to our understanding of how engineers affect species diversity and the functioning of ecosystems.
 The beaver is Nature's archetype ecosystem engineer; its clear-cutting and dam building activities dramatically alter the structure, function, and chemistry of wetlands. Research done by Drs. Justin P. Wright, Jones and Alex Flecker has shown that between one third to one half of vascular plant species in riparian areas in New York State's Central Adirondack Mountains depend on beaver-created habitats. When beaver make dams, they create a wetland while simultaneously destroying the streamside environment. Few plant species can live in both habitats; at the local scale, beaver engineering eliminates one set of plant species and replaces it with another. At the landscape scale, however, beaver markedly enhance plant biodiversity by increasing habitat diversity.
Future research in Chile's Tierra del Fuego region, where beaver were introduced in the 1950's, will shed light on how exotic ecosystem engineers affect plant diversity. The study will provide a contrast to the Adirondacks, where beaver have been making habitat for plants for thousands of years. Prior to beaver introduction, species in Tierra del Fuego had no history of beaver-induced riparian disturbance. Will beaver create a biological "desert" because there are no native plant species that can adapt to beaver wetlands? Will exotic wetland species invade the areas? Or will formerly rare native wetland species flourish in response to the wealth of new habitat created by beaver?
Like beaver, shrubs in Israel's dry Negev desert and cushion plants in the cold, dry, high Andes Mountains of Chile also modify habitat in ways that affect other species. Mounds of soil built by desert shrubs trap runoff water that is used by over 125 species of annual plants that grow on the mounds. In the Andes, cushion plants make a hostile environment warmer and wetter for the 32 forb species that can live inside cushions. Compared to "unengineered" areas, shrub mounds and cushions have much higher plant biodiversity and abundance. Unlike beaver, which create habitat for plant specialists, the shrubs and cushion plants make the environment more favorable for generalist plant species that can survive without them. This work, involving IES Adjunct Scientist Dr. Moshe Shachak and others in Israel, and Dr. Lohengrin Cavieres in Chile, is helping us understand how different engineers modifying different environments affect biodiversity.
By studying these and many other engineers — including digging porcupines, microbes that form soil crusts that generate runoff water, mollusk shells that are used as shelters, and burrowing crabs that change biogeochemistry — Jones and his colleagues hope to advance general knowledge of Nature's engineers. |
