Special Issue on Extinction of Organisms
Hiroyoshi Higuchi and Hideaki Karaki
Plants and animals are declining or becoming extinct in many parts of the world. They include both well-known species such as the giant panda (Ailuropoda melanoleuca) and the crested ibis (Nipponia nippon) and once common land snails, fireflies and small migratory birds. Factors leading to population decline or extinction include habitat destruction, chemical pollution, alien species, poaching, infectious disease, and global warming. In addition to their individual adverse impacts, these factors often overlap or interconnect in time and space, compounding their effects. In limited areas isolated by habitat destruction, for example, alien species and global warming more easily cause local populations to decline and become extinct.
There are also natural disasters such as volcanic activity and meteors that diminish or exterminate flora and fauna populations. However, extinction of species and groups sometimes give an opportunity for other species and groups to occupy vacant niche and similar life styles, which may lead to adaptive radiation in evolution. Organisms have repeated such evolution and extinction throughout geological history.
This special issue focuses on the extinction of plants and animals resulting from both human activity and natural disasters. In the first of seven articles, Hisashi Nagata reviews the history of extinction and the natural and human factors involved. Kazuto Kawakami looks at the impact of alien species on current ecosystems in the Ogasawara Islands, demonstrating interrelationships among different plant and animal species and pointing out what we could do about island ecosystem conservation and management. Haruo Ogi discusses the effects of fisheries by-catch on sea birds. TatsuyaKunisue and Shinsuke Tanabe detail the effects of chemical pollution on wild animals. Both factors are important in conserving biodiversity and in maintaining industries such as marine fisheries. Kazuya Ashizawa et al. focus on the population decline and extinction of plants growing along dry river beds and becoming rare as a result of human activities changing the structure of natural rivers. Yunshan Su deals with the history of the near extinction of crested ibises in China, and introduces successful recovery programs that may be useful in a similar Japanese program for the same species. Takashi Kamijo et al. detail the impact of volcanic activity on the vegetation of a small island, discussing ecosystem recovery.
We hope that this special issue will lead to better understanding of the unique interrelationships among plants, animals and the inorganic world, teaching how to conserve and manage the biodiversity around us. Extinction of one species may appear to have nothing to do with human lives, but the extinction of many plants and animals sets up serious conditions in maintaining life during the changing structure and function of ecosystems comparable in process to an aircraft losing rivets one by one and finally crashing at a critical point with massive loss of life.