Week #1 | Q1: Forests and Biodiversity
September 10th, 2009 at 17:57“Claims that there will be a massive loss of species as tropical forests are cleared are based on the relationship between habitat area and the number of species. Few studies calibrate extinction with habitat reduction. Critics raise doubts about this calibration, noting that there has been extensive clearing of the eastern North American forest, yet only 4 of its approximately 200 bird species have gone extinct. We analyze the distribution of bird species and the timing and extent of forest loss. The forest losses were not concurrent across the region. Based on the maximum extent of forest losses, our calculations predict fewer extinctions than the number observed. At most, there are 28 species of birds restricted to the region. Only these species would be at risk even if all the forests were cleared. Far from providing comfort to those who argue that the current rapid rate of tropical deforestation might cause fewer extinctions than often claimed, our results suggest that the losses may be worse. In contrast to eastern North America, small regions of tropical forest often hold hundreds of endemic bird species.”
I definitely recommend watching the TED Talk by Cornielle Ewango. I also found an interesting photo essay about endagered forest animals – the cute and cuddly ones that tend to grab the attention of the public. Have a look: Photo Essay from PBS Wide Angle
I’d like to hear from the rest of you. What are your thoughts on the topic of forests and biodiversity??
[References]
- Pimm and R A Askins Forest losses predict bird extinctions in eastern North America PNAS September 26, 1995 vol. 92 no. 20 9343-9347
- Brook, BW; Sodhi, NS; Ng, PKL. 2003 Catastrophic extinctions follow deforestation in Singapore Nature 424(6947):420-426.
September 11th, 2009 at 2:36 am
Thank you, Alison, for that very interesting email regarding temperate forest loss. You always hear about the constant discoveries of new organisms in the Amazon and other tropical rainforests and new medicinal/other uses for plants that were unknown previously. Our knowledge of the diversity of life in forest ecosystems is constantly growing and evolving and every time we cut down areas of the forest, we lose species and knowledge that we did not even know existed.
According to the World Wildlife Fund, as of October 2008, “up to 75 percent of Brazilian greenhouse gas emissions come from deforestation and forest fires – mainly in the Amazon. Because of this, Brazil is the fourth largest climate polluter in the world.” So not only does burning of these rainforests lead to tremendous loss of biodiversity for purposes of agriculture and other human activities, but it leads to hundreds of millions of tons of greenhouse gas emissions that warm our planet beyond average levels and feed a loop that leads to more warming and more loss of biodiversity. Climate Change Politics!!!
September 12th, 2009 at 8:06 pm
Pimm and Askins 1995 provides great insight into the extinction of avifauna (and species in general). I think its key contribution is the distinction between endemic (region restricted) and non-endemic species.
When I read Brook and Sodhi 2003, I thought that the reason the extinction of species in the rain forest is so high is the density of species within the deforested areas. This made sense when compared with the relatively low percentage of species that went extinct in the Eastern North American temperate forest. However, Pimm and Askins 1995 point out that it is not the number of species that was significant, it is the fact that all of the endemic species suffered extinction (Pimm and Askins 1995:9347).
I think this is significant when considering afforestation as well. The University of Kentucky Video “Reclaiming the Future: Reforestation in Appalachia”, talks about the success of reestablishing forests in surface mined areas. It is great that they are able to reestablish the hardwood forest for issues of clean water, erosion control, and flood prevention. However, the initial damage to the biodiversity of those forest (the extinction of endemic species) is something that cannot be fixed through reforestation.
September 13th, 2009 at 2:23 am
Unfortunately, surface mined areas in Appalachia (a relatively euphemistic term for blowing off 1,000+ ft of mountaintop to get at a seam of coal beneath) destroy wonderful forests which already exist on the tops of these mountains, thusly destroying already present forest ecosystems, and the coal companies often do a poor job of reforesting. Not to mention, upwards of 2,000 miles of streams have been buried since mountaintop removal mining was given the go ahead in Congress in the early 1970s and “clear-cut more than 1.2 million acres of deciduous forests” according to Jeff Biggers, a leading Appalachian mountaintop removal mining author in the U.S.
It is infinitely better, in my view, to not have to blow up mountains for a relatively little amount of coal to feed the U.S./Canada’s fossil fuel addiction and hope that we can reforest and regain biodiversity.
September 13th, 2009 at 7:18 am
In a perfect world surface mining would not exist and Appalachia wouldn’t have the environmental problems that result from it. “Reclaiming the Future: Reforestation in Appalachia” approaches the problem from a more realistic view. New coal dependent power plants are still opening in Kentucky. A recently formed consortium in Frankfort, KY is focused on capturing more of the emissions from coal plants (not creating alternative energy sources). Coal is going to be mined one way or another so lets find a way to mitigate the problems.
In the past coal companies did a poor job of reforesting because their initial steps were to compact the ground to decrease the erosion. However compacted ground does not promote root growth. The coal companies are working with researchers at the University of Kentucky and have taken effective steps toward reestablishing hardwood forests according to the 2003 reclamation guidelines.
These are not the original forest. They do not reclaim the original biodiversity that existed before the surface mining event. But, they do get the forests back to a state that they provide the goods and services that lawmakers are after. In the case of this video those goods and services include tourism, erosion control, water filtration, and sustaining the hardwood industry. Reclaiming the original biodiversity is secondary to those goals.
September 13th, 2009 at 4:16 pm
This is an excellent discussion. I hope more of our members chime in. This discussion of species diversity and density leans toward the perils of deforestation. Why is deforestation happening? Is there something within or underneath this ecosystem necessary for human industry? Yes – the forest provides necessary goods & services for human productivity. Please join me in the next post to discuss this topic.
September 14th, 2009 at 4:08 am
We all know the effects of deforestation in all parts of the world. So many studies are conducted and presented to all people concern in order to mitigate its ill effects not only on biodiversity but also in all human aspects such as food use, lumber. paper etc. From all the readings ive learned that even the height of the trees affects climate change ..it is not just planting trees per se to replace what have been cut down but the process and the timing of cutting trees affects earths natural behaviour and existence.
Mining with all the danger and negative effects on the environment is continuously being done in almost all parts of the world. Even places that are experiencing soil erosion and flooding cannot get away from it. Politics play a big role in this aspect especially for 3rd world countries. Mining does not only affects the areas being mined but even its surrounding body. Not just the forest but even the oceans and seas surrounding it and worst even the people employed in the mining industry.
With all the negative effects that deforestation brings based on so many studies and research done we can only hope it stops but on the other hand human existence depends on its produce.
September 14th, 2009 at 6:13 am
I agree that politics play a big role in mining, but also forest conservation. In general, I think that people’s primary priority is themselves. The TED Talk by Cornielle Ewango makes this evident when he is talking about the soldiers killing animals despite the laws of the Wildlife Reserve. He said, “they were doing whatever they wanted because they had power.” Coal mining for power, coltan mining for cellphones, and killing animals for various resources are all goals with an immediate payoff. As concern over the effects of deforestation grows maybe people will become aware of the long term consequences these actions have.
September 14th, 2009 at 1:40 pm
You ask why is deforestation happening? I suppose the simple answer was reinforced the other day when the world population topped 7 billion. At heart deforestation occurs because the 7 billion souls on the planet are seeking food, shelter and an income to support themselves. Yes, they could do it better. Yes, there are more sustainable ways. Ewango notes the importance of education, the folks in Kentucky underscore the need for research. I suppose the solution is an intellectual and practical one. Conduct research to search for sustainable ways to feed and clothe the 7 billion, and conduct research and education on ways not only for people to live, but reclaim what has been damaged. Of course, it would be nice too if the population wasn’t growing so quickly, at least then we might have a chance to educate people about better ways of meeting their needs.
September 14th, 2009 at 2:32 pm
Hey everyone! Nice to read the discussion going on. I just finished reading (and watching) a few things from the online course material. Got acquainted with a few interesting, but disturbing facts.
Each year about 16 million hectares of forested area disappears. Forests harbor tremendous biological diversity and have the potential to provide us with new crop varieties and medicines. Since fewer than 1% of tropical plants have been screened for possible use to medical science, ongoing deforestation results in permanent loss to science of other species before their value is recognized.
Amazon Rainforest (Brazil) has been described as the “single richest region of the tropical biome”. A single hectare of rainforest near Manaus (capital city, Amazonas, Brazil) yielded 235 tree species over 5 cm. in diameter and 179 species over 15 cm. in diameter. There are 2000 known species of fish in the waters of the Amazon Basin. This is eight times the number found in the Mississippi River system and ten times the number found in all of Europe.
Forests influence climate, soil system, and ground water which in turn influence the local biodiversity. For various reasons, forests are cut down which only disturbs the ecosystem. I’ve just read that the second growth forests have quite different character than the original. I’ll now read more about it.
September 14th, 2009 at 2:55 pm
Thorough and strong comments from everyone!! Now, Let’s steer this conversation in the ecology direction.
We’ve established that warmer humid tropical forests yield a higher diversity of flora (plant life) and fauna (animal life), not to mention decomposers and soil microbes. Therefore, removal of forest poses a cumulatively greater threat on species survival.
Q1 (a): Why do tropical forests harbor greater diversity than temperate?
Q1 (b): Beyond ethics, why is there any imperative to preserve rare species?
September 15th, 2009 at 8:27 am
I read on a few websites about why tropical forests contain greater diversity than temperate. Here is what I’ve learnt.
The great diversity in forests actually seems to be a result of the great diversity in forests- diversity depends on itself. Sounds strange but here’s how.
The multi-layered and complex nature creates an impressive range of habitats. Without the diversity of plants and habitat, shelter, and food, there would be no variety of animals. Without the animals for pollination, pest control and seed dispersal, the range of plant species could not persist.
Now, in tropical forests, the climate is much more hospitable and it is easier for animals to live and find food where temperatures remain fairly constant all year long. Tropical forests have a more elaborate structure than temperate forests. In the tropics, there are different kinds of trees which grow to different heights (due to lack of sunlight at the bottom) and there is a wide variety of other plants such as vines and epiphytes. All this variety creates more habitats which in turn make it possible for more animals to live in the same amount of space. Also, food sources including nectar, leaves and insects are available all year long in a tropical forest whereas they are available only seasonally in temperate forests.
Regarding rare species: Different species are part of different food chains. And a missing link in the food chain will influence the whole food chain in a significant way. Thus, one missing species may endanger others. Not just food chain, many species depend on other species for other reasons beneficial to them. For instance, pollens carried by insects, parasitic behavior between two species, etc. A species going extinct would be disastrous for different species in different ways.
September 15th, 2009 at 10:18 pm
Looking at the many groups who have charted species globally, it is obvious that many more species occur in the tropics. Tropical rain forests show a great deal of specialization among species fulfilling specialized ecological roles. I think you covered many of the reasons for the increased specialization above.
Another reason for diversity is speciation. Historic changes in global climate (i.e. glacial activity) caused periods of flooding and drying during glacial retreat. This would cause forest fragmentation, isolate populations and promote species formation (small gene pool, unique environment, evolutionary specialization is likely). Begs the question: is man’s deforestation of the planet bringing about new species?
As for why it is imperative to preserve rare species, there are economic reasons such as preserving for genetic diversity for selective breeding or utilizing yet unknown rare species that could provide medical treatments. I however agree with your comment about the connection between all species and the resultant impact of losing one.
September 15th, 2009 at 10:44 pm
What is Biodiversity and Why Is It Threatened?
Nutrient loading/pollution. Although nitrogen, phosphorus,
and sulfur occur naturally in the environment, their levels are increasing because of human activity, reaching concentrations that are putting species at risk. The increase stems from agricultural, industrial, and urban activities. According to the Environmental Literacy Council (www.enviroliteracy.org): “Pollutants in the air, water, and soil can influence organisms in many different ways, from altering the rate of plant growth to changing reproduction patterns to, in certain extreme situations, leading to extinction. Excess pollutants can also leave a species weakened, susceptible to other drivers of biodiversity
loss such as habitat change or competition from invasive species. These elements make nutrient loading
a complicated driver of biodiversity, especially within aquatic ecosystems where plants and marine organisms are disproportionately affected.”
Habitat change. Human activity has taken a heavy toll on the Earth’s biodiversity, through habitat destruction, degradation, and unsustainable management. For example,
thousands of years of human activity have reduced forest coverage from around 50% to 30% of total land area, and deforestation continues at an alarmingly high rate. Below are some alarming facts from the Millennium Ecosystem Assessment (millenniumassessment.org):
Almost 70% of Mediterranean forests, woodlands and • scrub were lost by 1990
In the Caribbean, average hard coral cover has • declined from about 50% to 10% in the last three decades
Some 35% of mangroves have been lost in the last • two decades
In the Arctic the average annual sea ice extent has • declined by about 8% in the past 30 years, with a loss of 15% to 20% in summer sea ice extent over the same period
Over-hunting and overexploitation. This is a serious threat to many species, such as marine fish and invertebrates,
trees, and animals that are hunted for meat. Humanity has always relied on nature for survival, and exploitation of species for food, clothing, and shelter has, in the past, always been sustainable. Unfortunately, today many species are hunted, trapped or killed above their rate of replacement
September 18th, 2009 at 11:06 am
In response to Allison’s question:
Q1. Why is tropical forests harbor greater diversity than temperate forests?
Its simply because climate of tropical forests which is higher than temperate tends to cater to living organisms more. Areas which has lower temperature is not conducive for most living organisms. See for us to prevent food from spoiling or to avoid growth of microbes we put them in the fridge. Meaning more living organisms adapts to tropical climate than with temperate..and this is just how nature goes.
Q2. We need to preserve rare species because as it is they are rare, meaning only few of them exist…if we dont give priority then definitely this will be extinct..Rare species live because they have reason and they have a purpose, they are included in the chain reaction of living organisms and they have adverse effects on the discontinuation of this chain reaction.
September 22nd, 2009 at 6:34 pm
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