Archive for the ‘biodiversity science’ Category
|Herbicide exposure causes male frogs to turn into female frogs
Monday, March 1st, 2010
How do you turn a male frog into a female frog that breeds with other male frogs? Expose them to herbicides that are routinely sprayed on agricultural fields worldwide.
Last year, Tyrone Hayes from UC Berkeley gave a talk at Bowdoin about his career’s work studying the impacts of endocrine-disrupting chemicals on amphibian development.
This week’s Early Edition of the Proceedings of the National Academy of Sciences features some of this research.1
Excerpts:
Atrazine is one of the most widely used pesticides in the world. Approximately 80 million pounds are applied annually in the United States alone, and atrazine is the most common pesticide contaminant of ground and surface water. Atrazine can be transported more than 1,000 km from the point of application via rainfall and, as a result, contaminates otherwise pristine habitats, even in remote areas where it is not used. In fact, more than a half million pounds of atrazine are precipitated in rainfall each year in the United States.
In addition to its persistence, mobility, and widespread contamination of water, atrazine is also a concern because several studies have shown that atrazine is a potent endocrine disruptor active in the ppb (parts per billion) range in fish, amphibians, reptiles, and human cell lines, and at higher doses (ppm) in reptiles, birds, and laboratory rodents. Atrazine seems to be most potent in amphibians, where it is active at levels as low as 0.1 ppb. Although a few studies suggest that atrazine has no effect on amphibians under certain laboratory conditions, in other studies, atrazine reduces testicular volume; reduces germ cell and Sertoli cell numbers; induces hermaphroditism; reduces testosterone; and induces testicular oogenesis. Furthermore, atrazine contamination is associated with demasculinization and feminization of amphibians in agricultural areas where atrazine is used and directly correlated with atrazine contamination in the wild.
Using an experiment where his team exposed frogs to a 2.5 parts per billion atrizine solution, here’s what they found:
Atrazine-exposed males were both demasculinized (chemically castrated) and completely feminized as adults. Ten percent of the exposed genetic males developed into functional females that copulated with unexposed males and produced viable eggs. Atrazine exposed males suffered from depressed testosterone, decreased breeding gland size, demasculinized/feminized laryngeal development, suppressed mating behavior, reduced spermatogenesis, and decreased fertility. These data are consistent with effects of atrazine observed in other vertebrate classes. The present findings exemplify the role that atrazine and other endocrine-disrupting pesticides likely play in global amphibian declines.
The main implication of this chemically induced sex switching is that it has the potential to disrupt breeding and contribute to the amphibian declines observed worldwide:
Although many studies have focused on death from disease and its role in global amphibian declines and sudden enigmatic disappearances of populations, virtually no attention has been paid to the slow gradual loss of amphibian populations due to failed recruitment. The present study suggests several ways that exposure to endocrine disruptors such as atrazine may lead to population level effects in the wild and contribute to amphibian declines. Certainly, the inability to compete for females and the significant decline in fertility in exposed males, as reported in the present study, will have a direct impact on exposed populations.
1Hayes, T. et al (2010) Atrazine induces complete feminization and chemical castration in male African clawed frogs (Xenopus laevis). Proceedings of the National Academy of Sciences. doi:10.1073/pnas.0909519107
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Photo credit: http://www.flickr.com/photos/arte/ / CC BY-NC 2.0
Tags: pesticides
Posted in biodiversity science, pollutants, toxics | No Comments »
Marine protected areas help coral reefs too
Wednesday, February 17th, 2010
As mentioned in an earlier post, marine protected areas (or MPAs) are a great idea for eliminating fishing pressures and allowing fish stocks to recover.
It’s less well known whether these underwater reserves help preserve reef-building corals, which most fish and other critters depend on one way or another—for habitat or food.
In today’s online issue of PLoS ONE (open accress), Elizabeth Selig and John Bruno conduct an analysis of MPAs worldwide and conclude that these areas are able to stem the loss of corals.1
That’s good news.
However, they offer this conclusion in the context of several important caveats:
MPAs can play a critical role in the protection of coral reef ecosystems, particularly fisheries. Our results suggest that MPAs are also generally effective in reducing or preventing coral loss. Nonetheless, we were not able to assess their effects on other metrics of reef health including changes in other key taxonomic species, coral composition, richness, reef heterogeneity and other factors that could also indicate that there has been a decline in reef health. MPA benefits may appear modest in the short term, but over several decades could lead to large and highly ecologically significant increases in coral cover as the cumulative importance of small annual effects becomes more important and the number of years of MPA protection increases. However, it remains to be seen whether the observed benefits of MPAs are sufficient to offset coral losses from major disease outbreaks and bleaching events, both of which are predicted to increase in frequency with climate change. Given the time lag for maximizing MPA effectiveness, implementing new MPAs and increasing enforcement should help maximize the ability of MPAs to prevent future coral loss.
Who cares? Lots of reasons:
- Coral reefs are incredible ecosystems. If you have never dived or snorkeled on a healthy coral reef, put it on your list of 10 things to do before you die. My recommendations are the Great Barrier Reef (Australia), the Cayman Islands, Hawaii, and the islands of the Netherlands Antilles. We owe it to future generations to preserve these ecosystems in the wild rather than in books and aquaria.
- Reefs are incredibly species rich. Protecting them protects a significant fraction of coastal marine biodiversity.
- Reefs are very productive ecosystems that provide a food source and habitat for thousands of species. Protect the corals, and you end up protecting many other species.
- Many coastal communities depend on reefs for their livelihoods (e.g., seafood harvesting and tourism). This makes reef management critical for economic as well as ecological sustainability. But, as this article suggests, local management is challenged by the fact that global threats, such as ocean acidification, disease, and rising temperature impacts on coral bleaching, may trump what local people can control.
1Selig ER, Bruno JF, 2010 A Global Analysis of the Effectiveness of Marine Protected Areas in Preventing Coral Loss. PLoS ONE 5(2): e9278. doi:10.1371/journal.pone.0009278
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Photo credit: One of my photos that you can see at my flickr site.
Tags: coral reef
Posted in biodiversity science, nature and culture, sustainability | 1 Comment »
New ideas about how changing vegetation at high latitudes can cause climate warming to accelerate
Thursday, January 7th, 2010
Most people have probably heard about positive feedbacks at high latitudes and why they matter:
- Warming thaws sea ice, and the decrease in the reflective ice surface causes more solar radiation to be absorbed by the oceans, thereby causing even more warming.
- Warming is causing the northward march of treeline. As boreal conifers in Canada, Alaska, and Siberia migrate into barren tundra, their dark foliage towers above bright snow in winter, causing the landscapes to darken, absorb more sunlight, and warm up, thereby enhancing regional warming.
A new study1 in the Early Edition of the Proceedings of the National Academy of Sciences (open access), indicates that other effects of forest changes might also matter.
Specifically, boreal forests and tundra may become more dominated by deciduous trees (ones that drop their leaves in autumn), which are usually found in warmer regions. What happens if we have a future Arctic dominated by these species?
Using a set of ecosystem and climate models, Abigail Swann and colleagues determined that a rise in deciduous forests would cause an increase in water vapor to the atmosphere (deciduous trees transpire—lose water through their leaves—more than conifers). This makes the atmosphere in the Arctic more laden with water vapor, which is a good greenhouse gas. This warming, in turn, induces further sea ice and snow loss, causing warming to happen more quickly. But wait, there’s more: Warmer, ice-free oceans also release more water vapor to the atmosphere, causing greenhouse warming to increase even more.
How big an effect? About 1 degree C in the Arctic, equivalent to increasing the atmospheric CO2 about 100 ppm in the atmosphere. They found that these changes in water vapor have about the same impact as the changes in reflectivity caused by the color of forest foliage overtopping snow in the tundra.
Things like this are reasons why when warming starts, it can accelerate faster than we think.
1Swann, A. (in press) Changes in Arctic vegetation amplify high-latitude warming through the greenhouse effect. Proceedings of the National Academy of Sciences
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Photo credit: Phil Camill (from my Flickr collection) http://www.flickr.com/photos/pcamill/ / CC BY-NC-ND 2.0
Tags: trees and forests
Posted in biodiversity science, climate change science, polar ice | 1 Comment »
In this week’s issue of Nature: Will species be able to keep up with climate change and how does this impact how we think about parks?
Thursday, December 24th, 2009
One of the outcomes of climate warming is that species will have to move to remain within climatic zones that match their physiological tolerances. Some common examples include the northward migration of boreal forest species into areas that are currently tundra and the upward migration of mountain species.
As Scott Loarie and colleagues note1 in this week’s Nature (subscription required), we often think of mountain ecosystems as being particularly threatened because alpine species have nowhere to go.
To analyze this challenge, they looked at the spatial gradients of temperature across land masses of the world. These data indicate how temperature changes over a known distance (temperature gradient = degrees C per kilometer).
Then, they used climate model model projections to determine how fast the temperature of a region will change (warming rate = degrees C per year).
By dividing the warming rate by the temperature gradient, they determined what they called the temperature velocity (kilometers per year)—which is basically represents how fast you (or another species) needs to move along the earth’s surface to maintain a constant temperature (check this division for yourself to see how the units cancel).
What did they find?
Posted in biodiversity science, climate change science, community conserved areas, risk analysis | No Comments »
When the levees break, we’ll have a more sustainable landscape again
Thursday, December 10th, 2009
We don’t ordinarily think about climate change and land use change as being a synergistic threat to society. However, the combination of impervious surfaces that increase runoff, declining wetlands, levees, and more severe storms pack a quadruple whammy that could lead to some major flooding in the future. From the cool adaptation work done in Keene, NH, we know that much of our infrastructure (roads, bridges, culverts) can’t handle the added stress of streams and rivers with higher discharge. We’re looking at a potential nightmare of increased costs associated with infrastructure damage.
In this week’s issue of Science, Jeffrey Opperman and colleagues argue1 that our historical paradigm of flood control with levees needs to fundamentally change to achieve a more sustainable socioecological system.
Their solution? Tear down some of the levees to allow some floodplains to flood. This can accomplish several goals:
(1) Flood risk reduction
- Move to flood-tolerant activities in floodplains so that we don’t have to spend so much on disaster relief.
- Storing water in floodplains takes the strain off downstream regions because floodwaters can naturally spill to where they are supposed to rather than swelling channelized rivers. Small amounts of land can accomplish this—they cite a study of the Illinois River showing that a floodplain of 8,000 hectares would drop the likelihood of flooding 26,000 hectares of cropland by 50%.
(2) Increased floodplain goods and services
- Several economic activities are conducive to periodic flooding: pasture, timber, and flood-tolerant biofuel crops, such as willow.
- Periodically flooded soils can also assist with reducing erosion and storing nutrients that would otherwise reach and pollute coastal oceans.
(3) Building resiliency to climate change
- They argue that reconnecting rivers to floodplains can help us adapt to climate change in ways that are socioeconomically beneficial. For instance, we presently have to keep some reservoirs partially empty to accommodate periodic flood waters. But partially filled reservoirs can’t generate as much hydropower or provide as much drinking water. If we used floodplains as a natural pressure relief valve, we can operate reservoirs closer to capacity and benefit economically.
Opperman and colleagues acknowledge that there are political hurdles, such as convincing some private landowners that flooding their land can be useful.
But there are creative solutions that have already been deployed. They cite Sacramento as an example: Some farmers allow their crops to flood, serving as a pressure-relief valve when rivers swell, thereby preventing more expensive damage. In return, the farmers are compensated for their crop loss. It’s a win-win situation that presumably costs less than dealing with infrastructure damage or having to build new infrastructure that handles greater flooding.
Another idea is to allow some of these areas to become wetlands and compensate people as part of a wetlands banking system to mitigate the loss of wetlands elsewhere. This would most likely have several ecological benefits, including increasing habitat for wetland-dependent species such as waterfowl and other migrating birds. It would also likely increase vegetation productivity and carbon storage.
It’s interesting to note that they don’t call for an end to economic activity or human use in floodplains. Sure, we probably want to stop building McMansions in flood-prone regions. However, there are several ways we can use floodplains for ecological and economic benefit. These will likely require compensation, but in the long run, it’s cheaper than having to re-tool major infrastructure to handle greater discharge with climate warming.
1Opperman, J.J. et al (2009) Sustainable floodplains through large-scale reconnections to rivers. Science 326:1487-1488.
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Photo credit: http://www.flickr.com/photos/doblonaut/ / CC BY-NC-SA 2.0
Posted in biodiversity science, climate adaptation, food and agriculture, risk analysis, solutions, sustainable development | No Comments »
In this week’s issue of Nature: Rethinking global conservation
Thursday, November 19th, 2009
Robert Smith and colleagues argue1 that it’s time to reorganize the approach to conservation in developing nations.
They are critical of academics and NGOs for missing what they think really matters—effective, on-the-ground research and policy development with strong local participation and buy in.
Part of this stems from the focus of academics. They cite as an example the work of Norman Myers and Conservation International, who published a now-famous map of biodiversity hotspots.
The map was marketed as a tool for identifying where conservation investment would have the biggest impact, but this involved playing down both how little was actually known about species distributions and that accurate global data sets on the costs of implementation were not available.
These limitations did not stop the map doing its main job, which was to raise funds and show broadly where Conservation International should target its efforts. In fact, the initiative has been extremely successful and helped to raise an estimated US$750 million for conservation within hot spots. But the hype led many academics to treat priority area setting as simply a question of working out what lives where. This led to many studies that took no account of how plans are implemented.
And part of it stems from traditional structures of NGOs, which, in Smith’s words,
[facilitates] the need to create a sense of urgency among donors lead[ing] to short-term funding and ‘quick and dirty’ projects, which rarely gain local long-term support. Second, NGOs tend to advocate their institutional methodology, rather than allowing local agencies to develop approaches that best match their needs. Third, NGO researchers find it easier to produce articles on broad-scale issues for high-impact journals, which helps to build scientific support for new campaigns, than to write papers about research on local issues.
What’s the new approach they advocate?
Posted in biodiversity science, community conserved areas, nature and culture, social science | No Comments »
Important social and ecological dimensions to conserving and restoring marine environments
Wednesday, November 18th, 2009
Since the industrialization of fishing in the 1970s, the combination of longlining, trawling, dredging, and other forms of seafood harvesting have decimated marine species populations.
Predatory fish, including tunas, marlin, cod, and sharks, have declined more than 80 percent (here and here) over the past twenty years as a result of overharvest and accidental bycatch. In the Caribbean alone, green turtle populations may have numbered over 90 million three centuries ago compared with 300,000 today.
That’s so staggering I have to repeat it—80% declines. This is some of the most visible evidence of global change on the planet. It’s almost unbelievable.
Because people preferentially remove top predators when harvesting seafood, this leads to what we call a “trophic cascade,” as the abundance of other species lower on the food chain adjust in response to the loss of predators. In cooler, temperate marine ecosystems, the loss of predatory fish and lobsters often causes an increase in sea urchins and gastropod species (e.g., snails). Many of these species are herbivores, grazing on algae. So an increase in their populations leads to a situation of algae overgrazing, sometimes creating what are known as “urchin barrens.” It’s analogous to a deforested area on land, where both habitat and food are lost.
We often don’t think about these connections—how removing tasty fish from the sea can lead to widespread loss in algae, causing ecological systems to collapse.
Over the past decade, marine protected areas (MPAs) have become a popular tool for slowing the decline in marine populations, especially in coastal areas where sensitive habitat (like coral and rocky reefs) and fishing grounds often overlap.
The idea of MPAs is simple: Cordon off an area and eliminate or restrict fishing within the zone. Over time, the populations of species (like fish) increase and animals get bigger. These animals can then disperse out of the protected areas into legal fishing zones where they can be harvested. In an ideal system, it’s a win-win situation—habitats and species are protected and sustainable fishing harvests can be maintained.
There are a few problems, however…
Problem 1: Most of these generalizations are derived from short term studies (< 3 years), that, while useful, may not tell the full story about how marine ecosystems change following protection.
Problem 2: New MPAs may have different histories, from lightly fished to severely depleted, leading to different post-protection legacies (i.e., we may not expect species recovery to be the same). This could skew our interpretation of how successful MPAs are. Enter the social dimension… As nations move to develop MPAs, fishers often co-opt good fishing grounds (ones that are often highly depleted) and leave the marginal, lightly fished areas for MPAs. Does this matter?
In the latest issue1,2 of Ecological Applications, Graham Edgar and colleagues report longer-term changes (up to 16-years) in MPAs located in southern (temperate) Australia. [Side note: Edgar (in Aussie, it's pronounced "aid-gaaah") also wrote one of the best Australian temperate marine taxonomy texts there is. So beautiful it makes a great coffee table book].
What did they find?
Tags: marine protected areas
Posted in biodiversity science, nature and culture, sustainability | 1 Comment »
Making development in the tropics more sustainable
Wednesday, October 28th, 2009
Nowhere is the intersection of nature and culture more apparent than in tropical communities developing around forestry. One of the outcomes of opening the forest to logging is the expansion of killing wild mammals for food—sometimes primates closely related to humans, such as gorillas and chimpanzees. This is known as the bushmeat trade. And logging roads provide easy access for legal and illegal hunters.
Although bushmeat hunting often makes the news (examples 1, 2, 3), we seldom hear about the underlying demographic and social factors that interact with bushmeat harvests. Learning more about these factors can empower us to develop sustainable solutions that slow or halt the loss of biodiversity.
In the Early View edition1,2 of Conservation Biology, Poulsen and colleagues examined the interaction between logging towns and bushmeat harvests in Congo.
For six years, they followed animal harvests and meals to see what controlled the rate of bushmeat harvests.
Their results were interesting…
Posted in biodiversity science, nature and culture, sustainability | No Comments »
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