Impacts of Catastrophic Earthquakes on the Insect Communities in Estuarine Mangroves, Northern Taiwan

As a catastrophic earthquake is unpredictable and occurs only occasionally, impacts on biotic communities are seldom known. Monthly changes in insect communities in the mangroves along the Danshui Estuary were monitored for more than 3 years from before and after two catastrophic earthquakes in Taiwan the Chi–Chi earthquake (M_L = 7.3) of September 21, 1999 and the 3–31 earthquake (M_L = 6.8) of March 31, 2002. Here we show that the Chi–Chi earthquake not only caused large declines in total individual number but also total species number of insects. It also resulted in greater variability among samples, and shifts in insect communities. Non-biting midges and rove beetles, whose immatures inhabited the riparian underground or aquatic sediments, were most severely affected. By 7 months after the Chi–Chi earthquake, the insect communities had recovered to a level comparable to that before the earthquake. However, the influence of the 3–31 earthquake on the insect communities was less severe. It is concluded that the more-severe impacts of the Chi–Chi earthquake than the 3–31 earthquake can be attributable to differences in ground shaking, occurrence time, biodiversity, and growing conditions of insects at those times.