Category Archives: Ecology

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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Dying Coral Reefs

by Krista Bergesen

With the global climate changes going on right now, it may not be surprising to know that the aquatic life is also being affected. Displayed in every vacation resorts catalog and ocean documentary, coral reefs have formed an integral part of the planet’s oceans, providing a food supply, habitat, and protection for many other sea creatures.

Sometimes, it is easy to imagine coral as the dead, funny shaped rock that can be seen when you go scuba diving. Surprising as it may be, coral are actually living animals that eat, breathe, and reproduce.

Often mistaken for plants, coral use tentacles to sting and capture their prey of small fish and small animals. Hard to imagine, right?

It may be interesting to note that coral also located all across global waters. In colder northern waters, the coral don’t generally settle down into the picturesque colonies of the equatorial waters, but are still there floating aimlessly throughout the water. Large colonies are formed in the presence of algae, where the coral can feed off of the algae’s products of photosynthesis. At the same time, the coral produce CO2 to feed the algae. Not having to capture prey anymore because of this mutualistic relationship, the coral then produce the calcium carbonate exoskeletons that people usually identify with the species.

Coral reefs may look rock hard and impermeable, but they are surprisingly fragile.

Myriads of creatures graze on and make their homes in the coral. And the coral are always dying and re-growing their structures because of the constant attack they are under. A very delicate balance of destruction and growth has been maintained for millions of years between the coral and the rest of the ocean. It figures that humans would mess it up.

Instead of carrying fresh, clean water to the oceans, rivers now carry agricultural waste. Nitrates, phosphates, sewage, etc. now pollute the water. Recent evidence has found that coral now faces disease susceptibility from the sediment accumulation and increased exposure to land-based pathogens.

It doesn’t stop there, global warming has, not surprisingly, caused problems as well. As coral and algae colonies evolved together in a very narrow temperature range, the algae have begun to produce poisonous oxygen compounds called “superoxides” because of the higher oceanic temperatures. The coral will consequently expel the algae only to starve and turn a deathly white, giving the process the name of “bleaching.”

Coral reefs only form a small portion of the vast oceans, but their presence showcases the biodiversity and intricacy of the ocean’s natural systems. Widespread coral bleaching as well as pollution will change the face of the oceans as we know it through extinction. And this type of change cannot be undone.

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Dangerous Dioxins

By: Lizzie Caldwell

According to Chemical And Engineering News, the US Environmental Protection Agency(aka EPA, largest government agency in the US to protect human health and the environment) has recently proposed to tighten its guidelines for remediation dioxins and related chemicals in soils.


Dioxins are chemicals that are extremely dangerous for humans. The full name is “polychlorinated dibenzodioxins”. This name sounds long and complicated, but let’s break it down.

“Poly” means multiple. “Chlorinated” means it has chlorine, so we know that a typical dioxin molecule has multiple chlorines as a part of it. We’re halfway there!
“Di” means two. “Benzo” is the prefix for “benzene”, which is a 6 carbon ring:


Benzene molecule.

The C is carbon, the H is hydrogen, and the lines represent that the two atoms are connected. Two lines means the connection is “stronger” than one line, etc. Beside it is its shorthand version, which is what is commonly used.


Benzene is the simplest carbon ring ever, and it is everywhere. It is used to make plastics, rubber, drugs, and dyes. It used to be in our gasoline, until we realized that benzene causes cancer. Thus, from this name, we already know that the molecule is bad. For the last part, “di” means “two”, and “oxin” is the prefix for oxygen; thus, polychlorinated dibenzodioxin has two benzene rings, two oxygens, and a variable amount of chlorine atoms(which can be anywhere from 1 to 8). These molecules are generally referred to as “dioxin” for short.

PCDD, or polychlorinated dibenzodioxin. (The “n” and the “m” just symbolize that there are chlorines present, it just depends on the dioxin as to how many chlorine atoms on each benzene ring.)

How is dioxin worse than benzene? This rule can be applied to any molecule: organic molecules that occur in nature, like benzene, break down rather quickly. Organic molecules with chlorines attached to them, like most dioxins, make the molecule very stable. Thus, while benzene causes cancer, it only lasts from 3 – 10 days before it breaks down and is no longer dangerous. Dioxin, on the other hand, lasts from 7 – 10 years(Dioxinfacts.org). Imagine how many cancer-causing molecules one individual can accumulate if they lived near a place that produced dioxin molecules!


One type of dioxin, called “tetrachlorinated dibenzodioxin”(that means it has 4 chlorines. tetra = 4) is a powerful herbicide.

Picture of TCDD(tetrachlorinated dibenzodioxin).

It kills vegetation by making it grow uncontrollably until it dies. It is a byproduct of the molecules used to make Agent Orange. It was used during the Vietnam war, and the dioxins are still found in their soil today. The National Toxicology Program defined it as a cancer-causing molecule, and has been linked with non-Hodgkin’s lymphoma, Hodgkin’s disease, and chronic lymphocytic leukemia. It has affected the lives of hundreds of thousands of people; Europeans, veterans who were also exposed, and now, residents of the state of Michigan.

How did dioxins get to Lake Huron? Normally, dioxins are created in manufacturing plants. Manufacturing plants use a lot of fire and heat to make whatever they need; and when heat and chlorine are present around organic molecules(like benzene, a 6-carbon ring), a reaction happens that creates dioxins. Manufacturing plants don’t mean to make dioxins, it’s just a by-product of their process to make the chemicals and products they want to sell to you.


One of the unfortunate characteristics of dioxin is that it is aromatic – which means that it evaporates into thin air, there it can be easily distributed. This is how dioxin ends up in close lakes, and in the soil. Dioxin is a very expensive and inconvenient responsibility that EPA cleaned up for years. In 1998, the EPA made it the company’s responsibility to clean up the mess, and they set up guidelines. Now, with new reports claiming that dioxins are also present in soil, EPA wants to strengthen its guidelines to include soil. Dow Chemical’s spokeswoman criticizes the new guidelines, saying that “Soils aren’t really a primary route of exposure”(Chemical and Engineering News, Jan 2010). Luckily for Dow, the EPA cannot implement these new guidelines until it finishes reassessing health and environmental risks associated with dioxins; but we can all agree we don’t want dioxins around, isn’t that right, Ukrainian politician Viktor Yushchenko?

Before dioxin poisoning                  After dioxin poisoning

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Too Cold for Turtles

By Kimmie Riskas

Florida wildlife authorities are reeling. The first two weeks of January
brought unseasonably cold water off the state’s coast, shocking a record
5,000 sea turtles into a catatonic, coma-like state. All seven species of
sea turtles are cold-blooded, tropically-distributed, and endangered.
Principally affected by the “cold-stun” were green turtles (Chelonia
mydas), which prefer warm, shallow water and are thought to be more
sensitive to changes in temperature. A number of loggerhead turtles
(Caretta caretta) were also rescued. Officials found the stunned turtles
floating in the water, unable to forage for food or move to avoid boat
collisions.

The coordinated rescue and rehabilitation effort combined six federal and state organizations, several non-profits, and innumerable volunteers in what is being called the “largest turtle rescue in history.”[1] One such organization, the Loggerhead Marinelife Center in Juno Beach, has treated more than 80 turtles since the crisis began—nearly double its annual amount. The turtles’ injuries range from hypothermia and starvation to trauma from boat collisions and dehydration. Even NASA is helping with the effort, reportedly loaning out heaters to a center run by the Florida Fish and Wildlife Conservation Commission.

Such an unexpected, massive influx of turtles is putting further stress on rescue centers that support long-term patients. To accommodate the victims of the cold-stun, Turtle Hospital flew five “permanent resident” turtles from their convalescent lodgings in the Florida Keys on a 4,700 mile flight to Weymouth Sea Life Park in Dorset, England. The turtles in question had sustained spinal injuries from boat accidents and require constant human care to survive.

Treatment centers from North Carolina to Texas have been working to revive the animals as well as release those that have been nursed back to health. With water temperatures climbing up from the frigid 30s, several groups of recovered turtles have been released near West Palm Beach since last Tuesday. The successful discharges are a welcome relief for the rescue centers, as more injured turtles are being brought in every day from all parts of the state.

The deaths of hundreds of juveniles could spell disaster for future populations of the critically endangered turtles, biologists warn. Largely due to vigilant conservation and improvements in fisheries regulation, Atlantic green turtle populations have been on the rise for the past twenty years. Loggerheads haven’t been so lucky; the number of loggerhead nests on Florida beaches has dropped by half after peaking in the mid 1990s[2]. Since sexual maturation takes between one to three decades, the consequences of these juvenile deaths may not be observable for a number of years, when those turtles’ absences in the breeding population pushes the species into further peril.

* * *

For news, photos, treatment centers, more information on the cold-stun and how you can help, please visit http://www.seaturtle.org/blog/mcoyne/000655.shtml


[1] DINAH VOYLES PULVER. News-JournalOnline, January 13 2010.

[2] OSHA GRAY DAVIDSON. Onearth.org, January 21 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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