Overexploitation
“Over-harvesting” redirects from here
- See related articles: Sustainability and Overfishing
- See related articles: Sustainability and Overfishing
Over-exploitation is a distinct ecological term and one of the five main activities threatening global biodiversity. In conservation ecology the term means the taking of biological resources, or organisms, in larger numbers than their populations can withstand[1].
The phenomenon of over-exploitation resulted in the gradual emergence of the concept of sustainable development and sustainability, which has built on a range of other concepts, e.g. ‘sustainable yield’. ‘eco-development’ and ‘deep ecology'.
All living organisms require resources to survive. Over-exploitation of these resources for protracted periods can deplete natural stocks to the point where they are unable to recover within a short time frame. Expanding markets and increasing demand, combined with improved access and techniques for capture, are causing the exploitation of many species beyond sustainable levels. In practical terms, if continued, it reduces valuable resources to such low levels that their exploitation is no longer sustainable and can lead to the extinction of a species, in addition to having dramatic, unforeseen effects, on the eco-system[2].
- Examples:
Overall, 50 bird species that have become extinct since 1500 (approximately 40% of the total) have been subject to over-exploitation[3], including:
- Great Auk- The penguin of the north, hunted for its feathers, meat, fat and oil.
- Carolina Parakeet - The only parot species native to the eastern United States, was hunted for crop protection.
- Reversal:
- Sea Otter
- During the 18th and 19th centuries, the sea otter was heavily exploited, prized universally for its exceptionally warm and tremendously valuable pelt, which could fetch a price of between $2000 – $2500 US dollars[4]. Fur traders hunted the sea otters so intensively for their skins, that they were exterminated over huge areas. Their disappearance led to dramatic changes in the environment. Sea urchins, with no otters to control their numbers, increased explosively. Urchins eat kelp and they began to destroy the underwater forests. As the kelp disappeared, so did the other animals that relied upon it. Soon all that was left was a bare seabed carpeted with urchins.
- One small group of 32 individuals survived in a remote cove and hunting the sea otters was eventually banned. Under heavy protection, those 32 multiplied to 2,377 repopulating the depleted areas, which eventually made a full recovery.
- In addition, with declining numbers of fish stocks, again due to over-exploitation, killer whales have experienced a food shortage and have been observed feeding on Sea otters, again reducing their numbers
Other threats to biodiversity
- Habitat loss, fragmentation and degredation
- Introduced species
- Pollution
- [Persecution]
- [Climate change]
See also
References
- ^ Oxford. (1996). Oxford Dictionary of Biology. Oxford University Press.
- ^ Frankham, R., Ballou, J.D. and Briscoe, D.A. (2002). Introduction to Conservation Genetics. Cambridge University Press.
- ^ The LUCN Red List of Threatened Species (2009).
- ^ Krebs, C.J. (2001). Ecology (5th ed.). Benjamin Cummings.