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The Ecology of Fear: Lessons for Conservation & Restoration

Spiders – apart from cunningly spin webs to trap other innocent insects and eating male spiders after fertilization, they can play an important role in maintaining the soil fertility. An interesting experiment was done by researchers at the University of Jerusalem who wanted to bridge ecology and biogeochemistry to find about how food web structure can affect nutrient cycling gave some interesting results. The researchers housed one set of grasshoppers with predatory spiders, which had their mouth- anatomy glued shut so that the experimental grasshoppers could not be eaten, while the other set was housed with no spiders. Post-death the decomposing bodies of grasshoppers were added to soil with leaf litter. After three months, the plant matter in the soil seeded with afraid grasshoppers had decomposed 200 per cent less than the plant matter in soil treated with unafraid grasshoppers. The stressed insects die with less nitrogen in their bodies, providing fewer nutrients to soil slowing the rate of plant- matter decomposition. This study is an example of the Ecology of Fear.

From crickets and spiders, let’s move to a larger picture. To see how the ecology of fear works in a complex network of an ecosystem. The Yellowstone National Park would be the most ideal location, being one of the most diverse national parks in the world. Forestry scientists from Oregon University found that the elimination of wolves had removed the natural element of fear from these ecosystems. It has triggered a cascade of ecological effects on everything from elk populations to beaver, birds, fish, and even stream systems- and helped lead directly to the collapsing health of aspen and some other tree species and vegetation. Elk was found to alter their behaviour due to the perceived threat of wolves dedicating energy to maintaining a constant vigilance and keeping open avenues of escape. As a direct result, the elk graze in less sensitive habitats, meaning that certain threatened shrubs and trees are recovering, along with smaller animals like beavers.

Very similar observations have been made with sharks. When there are large amounts of sharks present in an area, dugongs tend to avoid shallower water where they’re more vulnerable, allowing meadows of seagrass in those areas to thrive, along with other plants and marine life that depend on them.

All these examples of the ecology of fear portray the delicate balance and intricacy of the ecosystem. Conservation and restoration measures acknowledging this factor have proved to give very effective results. Understanding that each organism is a strand in the immensely complex network of ecosystem and thus each species is significant and vital for the overall health of the ecosystem is the baseline idea behind the concept. A holistic approach to conservation could be the answer to our current problems of conservation and restoration.

REFERENCES

Hawlena, D., Strickland, M. S., Bradford, M. A., & Schmitz, O. J. (2012). Fear of predation slows plant-litter decomposition. Science, 336(6087), 1434-1438.

Ripple, W. J., & Beschta, R. L. (2004). Wolves and the ecology of fear: can predation risk structure ecosystems?. AIBS Bulletin, 54(8), 755-766.

Wirsing, A. J., Heithaus, M. R., & Dill, L. M. (2007). Fear factor: do dugongs (Dugong dugon) trade food for safety from tiger sharks (Galeocerdo cuvier) Oecologia, 153(4), 1031-1040.

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