Tag Archives: extinction

Rising Sea Levels and the Bengal Tiger

Endangered Species Case Study: Bengal Tiger
by Krista Bergesen

Tigers have long thrived in a variety of habitats across the Asian continent. Extremely adaptable, these solitary hunters have found their niche in extremely different climates: from the the frozen forests in Russia to the much hotter, tropical climates in India and Indonesia.

However, at this time, it seems that tigers are losing habitat at too quick of a pace to stay a viable species. Because of human activities, tigers have been pushed into a small portion, only 7%, of their historic habitat, leaving only around 3,200 tigers left in the wild.

The Bengal tiger has long occupied vast areas of Indonesia and India, and an especially large portion in what is called the Sundarbans. This large forest of mangroves provides food and shelter to many different species, including around 400 Bengal tigers, an extremely large number  given the already dwindling population as a whole. Although the numbers are not conclusive, it is estimated that around 10% of the entire tiger population lives in this large stretch of mangrove forest.

The controlled environment of the Sundarbans strongly promotes biodiversity. Fish use the area beneath the submerged mangrove roots to breed, while the trees shelter the coastal and intertidal zones from cyclones, wind damage, and storm surges. As many as 50 reptile species, 120 fish species, 45 mammal species, and 300 bird species call this forest their home. And tigers here play a very singular role in the ecosystem, swimming between the islands of this area and collecting food from the marine life in addition to spotted deer for their diet.

This area, unfortunately, is in danger. And not just from poachers or deforestation, but from rising sea levels. Global warming has done it yet again. By the year 2070, the sea levels around the Sundarbans are predicted to rise 11 inches. With this drastic rise, the environment will no longer adequately support the tigers or many other species that thrive within the mangroves. And with accelerating habitat destruction, this large forest may not even exist in 50 years at all.

The effects are projected to be devastating. From the estimated 400 tigers alive now, the population is predicted to sink to around 20 breeding tigers because of the 96% decrease in habitat. In addition to the continued effects of poaching and deforestation, the rising sea levels could lead this subspecies into extinction, joining the 2 tiger subspecies already extinct.

The situation seems hopeless. However, local governments have the chance to conserve the threatened mangrove forest as well as curtailing the rampant poaching problem. Also, the region can increase sediment delivery and freshwater flows to the Sundarbans for replenishment of the land. Although this is probably easier said than done, it is hopeful that the situation can be resolved through progressive laws and environmental protection efforts. But it doesn’t end there. The globe as a whole needs to reduce greenhouse gas emissions, otherwise the above efforts and changes will be ineffective in saving the Sundarbans, and with it, its rich biodiversity.

Sources:

Poston, Lee. “Climate Change Threatens to Wipe Out One of World’s Largest Tiger Populations this Century” <http://www.worldwildlife.org/who/media/press/2010/WWFPresitem14891.html&gt; 19 Jan. 2010. 22 Feb. 2010.

“New Study Shows Bengal Tiger’s Habitat in Danger.” <http://www.worldwildlife.org/who/media/press/2010/WWFPresitem14914.html&gt; 19 Jan. 2010. 22 Feb. 2010.

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Plant and Animal Invaders

Plant and Animal Invaders
by Krista Bergesen

The year 2010 marked the beginning of the UN’s International Year of Biodiversity in response to the present planet’s extinction crisis. But after a while, a person could start to wonder: what are some of the driving forces behind the loss of biodiversity on the planet? Well, there’s fossil fuel burning and deforestation to name a couple. That isn’t the end of the story, however.

Humans may have messed around with the ecological system even more than you may think. The increase in travel and importation going along with a global economy has allowed the transportation of many non-native plants and animals to sensitive habitats.

And that is just the beginning. These invasive species consume the resources of the original flora and fauna in the system. According to the International Union for Conservation of Nature, 40% of species are recorded as extinct because the effects of invasive species.

This has even caused economic damage. Yearly, 1.4 trillion dollars are spent worldwide on control measures and habitat restoration because of the havoc wreaked on the environment. The US itself suffers a loss of 138 billion dollars a year just for its own issues with invasive species.

As already stated, the unattended and unmanaged environment containing invasive species can result in extinction of native species. What’s worse is that the changing global temperatures are enabling non native species to gain a stronger foothold in their new environments.

For example, British Columbian forests are being plagued by mountain pine beetles, whose population has invaded and subsequently increased in number due to the milder winter temperatures. Normally, these creatures would not survive in such a harsh climate, but with the increasing global temperatures they can move further north with increasing speed in destructive numbers. Predictions have estimated that this beetle will be responsible for the devastation of 80% of pine in the province by the year of 2015.

Eradication and control efforts are commonly made against invasive species. However, in areas with multiple introduced species, it can become very difficult to foresee the consequences of various control efforts. Eradicating one invasive species may actually lead to increased damage from another.

The New Zealand ecosystem, only recently populated by humans, has faced many difficulties because of human-introduced species. Their many “management responses” dealing with the threats of invasive plants and animals have often had unforeseen consequences. Livestock, brought by human colonists has limited the habitat of Whitaker’s skink. However, when livestock was removed from certain areas to restore skink populations, predators moved in only to further reduce the skink numbers.

Despite difficulties faced in ecological restorative efforts, they are exceedingly important in maintaining diversity. To be successful, the control projects must be “intensive” and continued for long periods of time, otherwise any progress made with restoration will be lost. Also, when considering a project, all possible outcomes must be considered to ensure that more negative effects on the system are not accidently created.

It should be noted that many successful control efforts in have been documented, and that native species is preservation can be achieved. As global temperatures rise, these efforts will be more and more essential to preserving biodiversity and help slow the accelerating rates of extinction worldwide.

Berger, Matthew. “Invasive Species Threaten US Biodiversity” Guardian Environment Network. <http://www.guardian.co.uk/environment/2010/jan/05/invasive-species-us-waterways>
5 Jan 2010.

Strong, Donald and Robert Pemberton. “Biological Control of Invading Species–Risk and Reform.” Science Magazine. Vol. 288: 1969-1970. 16 Jun 2000.

Norton, David. “Species Invasions and the Limits to Restoration: Learning from the New Zealand Experience.” Science Magazine. Vol. 325: 569-571. 31 Jul 2009.

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In the Middle of a Mass Extinction

by Krista Bergesen

The phrase “mass extinction” can conjure some scary images. Maybe one person imagines a giant meteorite hitting the earth and killing all of the dinosaurs, while another person may think of the last article they read about the human impact on the environment. Either way, it doesn’t sound like a very upbeat topic.

But what is mass extinction anyway? For one, it encompasses much more than what many of us can fathom. It usually means that at least 75% of the species globally have or are dying out on the planet. The planet would never have the same species again, and it would take around 10 million years to regenerate the same species diversity that had once existed.

It may not surprise a lot of people to know that we are in the midst of the largest extinction since that of the dinosaurs. Magazines, television ads, and even movies have tried to spread the word. Some of the messages are depressing, some are inspirational. Either way, the message is clear: the extinction is happening and humans are a major cause.

In a recent study done on the mammals in North America and their extinction rate, a group of scientists concluded that with the migration of humans to the North American continent the “normal” species’ richness declined 15-42%. Going by the definition of a mass extinction said earlier, North American mammals are already one fifth to one half of the way there. And this was before the effects of industrialization.

The anthropogenic time period, or era in which humans have existed is referred to as the “Holocene Period.” When compared with fossil samples from preceding periods, it was concluded that the beginning of the dominance of humans on the North American continent is concurrent with the decline of mammalian diversity. There has been an extinction of nine subspecies and a significant loss of habitat for other North American mammals because of the predominance of humans on the landscape.  Also, the growth of human biomass has matched the decline of the biomass of other species. Thus, the diversity of mammals, as well as the diversity of other animals is being greatly threatened by human development.

Although the study done on North American mammals is by no means representative of the whole world, it does establish one important fact. It quantifies the extinction of a certain type of animal that stands for an important part of the animal population.

In 2006, an estimate was put out by the World Conservation Union stating that 844 species had gone extinct in the past 500 years, attributing the causes to “habitat change, over-exploitation, the introduction of invasive species, nutrient loading, and climate change.” Techniques used for agriculture homogenize the plant life, and often can rid animals of their habitat or food sources. And none of these problems have shown any sign of slowing.

So what can be done? It’s pretty obvious that things have not been going well for other species on the planet with the rapid growth of the human population. For one, awareness, along with conscious action will be very important. Reserves for the natural environment need to be maintained and added to, as well as a development of sustainable energy and food production practices. Sounds difficult, and maybe impossible at this point. But the point is that something needs to be done now or the planet will face a loss of many diverse and important creatures.

Sources:

Reuters. “Humans spur worst extinctions since dinosaurs.” ABC News Online.< http://www.abc.net.au/news/newsitems/200603/s1596740.htm >. 21 March 2006.

Carrasco, Mark, et al. “Quantifying the Extent of North American Mammal Extinction Relative to the Pre-Anthropogenic Baseline”. PloS one. 2009. Volume 4; Issue 12. 8331.

Barnosky, Anthony. “Megafauna biomass tradeoff as a driver of Quaternary and future extinctions.” The National Academy of Sciences of the USA. 2008. Volume 105. 11543-11548.

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Tryone Hayes and the global decline of amphibians

By: Justin Scioli

Dr. Tyrone Hayes is the kind of guy that is impossible to not admire. While growing up, a young Hayes spent his free time chasing frogs, his greatest passion, through the swamps and woodlands of his native South Carolina. He took his passion in Herpetology, the study of amphibians and reptiles, all the way to Harvard University to receive his undergraduate biology degree and to UC Berkeley to receive his doctorate and later to join the faculty. But the most admirable thing about Hayes is that he is a hard-nosed scientist, keeping his data unbiased even when the results are ugly truths that many people don’t want to face. And some of Hayes’ findings are quite ugly, especially to some powerful chemical corporations.

Hayes has been primarily studying the effects of chemicals, specifically pesticides, on development of amphibians. Many of his studies examine the effects of Atrazine, the most commonly used herbicide in the United States and one of the most common in the entire world. Atrazine is used to kill weeds in crops, however like all chemical pesticides it is easily spread through runoff. This runoff carries the potent pesticide into nearby rivers, lakes, and other bodies of water where it affects the flora and fauna there.

In 2002, Hayes published a study that examined the effects of Atrazine on the sexual development of African clawed frogs (Xenopus laevis) which have been introduced in North America. The results showed that even a very small amount of Atrazine was capable of causing a tenfold decrease in testosterone levels in male frogs, making them into hermaphrodites. Hayes believes this is because Atrazine induces Aromatase which promotes the conversion of testosterone into estrogen. This basically means reducing the stuff that makes boys into boys. Of course this has detrimental effects on the sex ratio of frog populations, and Hayes believes the use of pesticides could be a major factor in a worldwide decline in amphibian populations.

Since the 1980’s amphibians, like frogs and salamanders, have been declining severely. The rate of extinction in this group is 211 times the background extinction rate, meaning that they are going extinct 211 times more frequently than rate of natural extinction recorded due to geological and ecological changes in the environment. Many causes are believed to contribute to this massive decline. In addition to pesticides, culprits such as sound pollution that interferes with vocal communication, the spread of a fatal fungus, as well as climate change and habitat destruction that is affecting nearly all life on earth. The loss of an entire class of animals would spell serious damage to food webs from the tropics to temperate regions, and some ecosystems are dependent on amphibians as an entire trophic level of organisms. What Hayes and other biologists are extrapolating from the amphibian decline is even closer to home for us.

Amphibians are a very sensitive group, largely because they absorb water through their skin. This makes them an ideal “canary in the coalmine” for seeing the levels of chemical toxicity due to pollution in a given environment in which they are naturally occurring. When amphibians are dying, that is a good sign that toxicity levels are increasing. More and more studies are showing the detrimental effects of pesticide exposure on human health. In a talk given in 2008, Hayes discussed that levels of toxicity are shown to be lower in breastfeeding women. This is due to the fact that they are excreting toxin through their breast milk and thereby transferring it to their child. Frog or human, developmental stages of life are much more sensitive to toxic pesticides than adults. This spells compromised immune systems for the young and developing, and the fact that Atrazine is the most common contaminant in ground, surface and drinking water is concerning for many.

The European Union banned the use of Atrazine in 2004. The United States on the other hand continues not just to use it in agriculture but to allow a given concentration of it in drinking water. Recent studies show that the allowed amount of Atrazine can lead to low birth rates, birth defects and menstrual problems. Despite this, the EPA continues to suggest that there is no need for concern and is not officially suggesting water filters to pregnant mothers. They will not review those studies until next year at the earliest, and in the meantime pregnant women throughout the U.S. could be sipping up Atrazine any time they drink from a tap.

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