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Ocean acidification negatively affects coral establishment

Monday, November 8th, 2010

When CO2 from fossil fuels accumulates in the atmosphere, some of it dissolves into the oceans where it reacts with water to form a weak acid (H2CO3) —carbonic acid— that lowers seawater pH and makes it increasingly difficult for corals and other calcitic organisms to form their calcium carbonate (CaCO3) skeletons.

A new study in the Proceedings of the National Academy of Sciences by Rebecca Albright and colleagues suggests that the negative effects of ocean acidification don’t stop with adult organisms.  The colonization and establishment of juvenile corals appear to be severely impacted.  They studied a common coral found in the Caribbean—Acropora palmata (elkhorn coral, which is not the same as the staghorn coral species pictured above).

A snapshot of their results:

  • When corals were grown in seawater with elevated CO2 to simulate mid- and late-century emissions trends, they found a 52% and 73% decline in coral settlement success, respectively.
  • For corals that settled and started growing, they found that the mid- and late-century CO2 levels reduced early growth by 39% and 50%, respectively.

This is potentially very bad news because if you shut down the capacity for new corals to establish, you reduce the ability of coral reef systems to persist in the face of disturbances like hurricanes, wave action, nutrient pollution, bleaching, and disease.

Rebecca Albright, Benjamin Mason, Margaret Miller, and Chris Langdon (2010). Ocean acidification compromises recruitment success of the threatened Caribbean coral Acropora palmata Proceedings of the National Academy of Sciences

ResearchBlogging.org

Photo credit:  One of my photos from the Great Barrier Reef.  Check out my entire collection at Flickr.

Posted in biodiversity science, climate change science, oceans | No Comments »

The diversity of values held by conservation scientists and why this matters

Monday, November 1st, 2010

Right up there with climate change, biodiversity conservation is one of the most challenging issues at the intersection of nature and culture.  Part of this challenge arises because of genuine differences in how people value other species.

In an interesting forthcoming article in Conservation Biology, Chris Sandbrook and colleagues at Cambridge University argue that these value differences not only show up in society at large, but among conservation professionals, who—like climate scientists—are drawn to the possibility of developing scientific consensuses to inform policy debates:

Conservation biology has been called a crisis science and a mission-driven discipline. Both the mission, and its urgency, seem clear, and there has been a substantial increase in activities intended to address the rapid decline in the variety of life on Earth at all levels of biological organization (structure, composition, and function). Nevertheless, there are tensions within the field about the values that underpin the conservation mission, particularly concerning the nature and singularity of these values and the role of values when conservation professionals try to inform or influence policy.

Recently, the values held by conservation professionals themselves have been debated. Conservation professionals often refer to both instrumental values (the usefulness of nature for humans) and noninstrumental or intrinsic values, and there may be an element of opportunism when they do so. Thus, although some may privately base the positions they hold on intrinsic values, they may espouse use-value arguments in public, adapting arguments to the interests of their audience. Some call for conservation scientists to return to a conservation ethic derived from intrinsic values

…[Others] propose a more pragmatic engagement with material values of nature in their focus on what they see as the “hard socioeconomic realities in real-world conservation problems.” The environmental philosophy of pragmatism, with its acceptance of both intrinsic and instrumental values of nature, is the hallmark of adaptive management

To study values held by conservationists, the research team posed a set of values to scientists and asked them to rank the degree to which they agreed or disagreed with the statements (Q methodology).  The responses were then run through a set of statistics (factor analysis) to distill the huge pile of value-by-person data into four overarching factors that summarized the main values held.

Their results suggest that consensus building may not only be difficult, it may be counterproductive…

(more…)

Posted in biodiversity science, communication and framing, environmental ethics, nature and culture, policy, population, race and class, science advocacy, social science, sustainable development | No Comments »

More on genetically modified (Bt) corn: Is it an economic boon to all corn farmers?

Thursday, October 7th, 2010

There’s a new paper in this week’s issue of Science that suggests that growing a landscape mixed with genetically modified (GM) Bt corn and non-GM hybrid varieties of corn can be mutually beneficial to all corn farmers.

Why?  They argue that the populations of GM corn knock down the populations of insect herbivores enough that, on a landscape scale, this effect spills over to nearby farmers growing non-GM corn, which raises yields and profits:

[W]e estimate that cumulative benefits for both Bt and non-Bt maize growers during the past 14 years were almost $6.9 billion in the five-state region (18.7 million ha in
2009)—more than $3.2 billion in Illinois, Minnesota, and Wisconsin, and $3.6 billion in Iowa and Nebraska. Of this $6.9 billion total, cumulative suppression benefits to non-Bt maize growers resulting from O. nubilalis [European corn borer] population suppression in non-Bt maize exceeded $4.3 billion—more than $2.4 billion in Illinois, Minnesota, and Wisconsin, and $1.9 billion in Iowa and Nebraska—or about 63% of the total benefits.

They suggest that the populations of non-GM corn also benefit the Bt corn farmers because the non-GM corn maintains a genetically diverse population of insects, helping prevent the evolution of herbivores resistant to Bt corn.

These results are interesting and —if they hold—could be an example of how GM crops bring environmental and social benefits.  A good outcome for all.

However, there are a couple of important things to consider:

(1) The notion of mixing crop types to minimize herbivory is the one of the fundamental tenets of traditional agroecology and organic agriculture, but instead of relying on GM crops, it could be done with a mix of hybrid crop varieties that doesn’t risk the potential environmental side effects of Bt corn or other unexpected outcomes of GM crops.  This is a major value judgment.   Does having one GM crop and a few dominant corn varieties count as diversity when the Midwest becomes a giant sea of maize?  As I explain in #2 below, probably not.  Could we achieve the same kind of insect pest management using a diversity of non-GM crops?  Yes—it happens all the time in midwestern organic farms.  Multi-crop organic farming is often more labor intensive than industrial agriculture, making the food produced more expensive.  But do we only care about cheap food?

(2) I’ve lived in southern Minnesota, where it’s a giant rotating monoculture of corn and soybeans.  If you look at Figure 1 in this paper, you will see that 50-75% (or more) of the corn grown in many regions of states like Iowa, Nebraska, and Minnesota is Bt corn.  When so much of your landscape is Bt corn, the evolution of resistance to Bt is most likely inevitable, as we saw in a previous post with the use of Roundup-ready crops like soybeans, which are often grown in rotation with Bt corn in these regions.   Acknowledging this fact of life, EPA recommends mixing GM and non-GM corn in an effort to delay the evolution of resistance, not prevent it:

To delay evolution of resistance, the U.S. Environmental Protection Agency (EPA) mandated that a minimum 20 to 50% of total onfarm maize be planted as non-Bt maize within 0.8 km of Bt fields as a structured refuge for susceptible O. nubilalis. Use of non-Bt maize refugia is an important element of long-term insect resistance management.

…Sustained economic and environmental benefits of this technology, however, will depend on continued stewardship by producers to maintain non-Bt maize refugia to minimize the risk of evolution of Bt resistance in crop pest species, and also on the dynamics of Bt resistance evolution at low pest densities and for variable pest phenotypes.

 

Hutchison, W., Burkness, E., Mitchell, P., Moon, R., Leslie, T., Fleischer, S., Abrahamson, M., Hamilton, K., Steffey, K., Gray, M., Hellmich, R., Kaster, L., Hunt, T., Wright, R., Pecinovsky, K., Rabaey, T., Flood, B., & Raun, E. (2010). Areawide Suppression of European Corn Borer with Bt Maize Reaps Savings to Non-Bt Maize Growers Science, 330 (6001), 222-225 DOI: 10.1126/science.1190242

ResearchBlogging.org
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Photo credit: Ian Hayhurst

Posted in biodiversity science, food and agriculture, health, organic, risk analysis, toxics | 2 Comments »

First global marine species census complete: More incredible images of our natural world

Monday, October 4th, 2010

MSNBC is running a story with a stunning set of underwater images documenting marine species from the most recent census efforts:

Scientists wrapped up their first global census of sea life today, documenting an underwater world that turns out to be livelier and more connected than they thought it would be when they began the project 10 years ago.

The raw numbers behind the $650 million Census of Marine Life are impressive enough: Almost 30 million observations by 2,700 scientists from more than 80 nations spent 9,000 days at sea, producing 2,600 academic papers and documenting 120,000 species for a freely available online database.

Australian marine ecologist Ian Poiner, who chairs the project’s steering committee, said the results will serve as a “global baseline” for assessing the state of the ocean’s species over the decades to come. “That’s not only something that wasn’t available in 2000,” he told me from London, where the census’ final results were shared with the world today. “Many said it was too big a challenge and could not be done.”

Read more.

Posted in biodiversity science, oceans | No Comments »

New insights on global threats to water security

Wednesday, September 29th, 2010

Water security is making a bit of a splash this week.  CNBC ran this story on the water crises in western U.S. states, where the region is possibly closing in on a day of reckoning, as described by Felicity Barringer in the NY Times, and creating a climate of pessimism among some western water managers.

The scientific community is also weighing in.  C.J. Vörösmarty and colleagues published a review paper in this week’s issue of Nature in which they evaluate the worldwide risk of water security and threats to aquatic biodiversity (edited slightly to remove citations and statistics):

We find that nearly 80% (4.8 billion) of the world’s population (for 2000) lives in areas where either incident human water security or biodiversity threat exceeds the 75th percentile. Regions of intensive agriculture and dense settlement show high incident threat, as exemplified by much of the United States, virtually all of Europe (excluding Scandinavia and northern Russia), and large portions of central Asia, the Middle East, the Indian subcontinent and eastern China. Smaller contiguous areas of high incident threat appear in central Mexico, Cuba, North Africa, Nigeria, South Africa, Korea and Japan. The impact of water scarcity accentuates threat to drylands, as is apparent in the desert belt transition zones across all continents (for example, Argentina, Sahel, Central Asia, Australian Murray–Darling basin).

What is the disparity of risk between rich vs. poor nations?

Most of Africa, large areas in central Asia and countries including China, India, Peru, or Bolivia struggle with establishing basic water services like clean drinking water and sanitation, and emerge here as regions of greatest adjusted human water security threat. Lack of water infrastructure yields direct economic impacts. Drought- and famine-prone Ethiopia, for example, has 150 times less reservoir storage per capita than North America and its climate and hydrological variability takes a 38% toll on gross domestic product (GDP). The number of people under chronically high water scarcity, many of whom are poor, is 1.7 billion or more globally, with 1.0 billion of these living in areas with high adjusted human water security threat.

They also argue that as wealth increases in a nation, the apparent ability to deal with water security issues improves, leading to the perception that threat level is declining:

Contrasts between incident and adjusted human water security threat are striking when considered relative to national wealth. Incident human water security threat is a rising but saturating function of per capita GDP, whereas adjusted human water security threat declines sharply in affluent countries in response to technological investments. The latter constitutes a unique expression of the environmental Kuznets curve, which describes rising ambient stressor loads during early-to-middle stages of economic growth followed by reduced loading through environmental controls instituted as development proceeds. The concept applies well to air pollutants that directly expose humans to health risks, and which can be regulated at their source. The global investment strategy for human water security shows a distinctly different pattern. Rich countries tolerate relatively high levels of ambient stressors, then reduce their negative impacts by treating symptoms instead of underlying causes of incident threat.

Biodiversity threats from river use appear to be significant globally:

The worldwide pattern of river threats documented here offers the most comprehensive explanation so far of why freshwater biodiversity is considered to be in a state of crisis. Estimates suggest that at least 10,000–20,000 freshwater species are extinct or at risk, with loss rates rivalling those of previous transitions between geological epochs like the Pleistocene-to-Holocene.

And what about future prospects?

We remain off-pace for meeting the Millennium Development Goals for basic sanitation services, a testament to the lack of societal resolve, when one considers that a century of engineering know-how is available and returns on investment in facilities are high. For Organisation for Economic Co-operation and Development (OECD) and BRIC (Brazil, Russia, India and China) countries alone, 800 billion US dollars per year will be required in 2015 to cover investments in water infrastructure, a target likely to go unmet. The situation is even more daunting for biodiversity. International goals for its protection lag well behind expectation and global investments are poorly enumerated but likely to be orders of magnitude lower than those for human water security, leaving at risk animal and plant populations, critical habitat and ecosystem services that directly underpin the livelihoods of many of the world’s poor.

…with a not-so-comforting conclusion:

Left unaddressed, these linked human water security–biodiversity water challenges are forecast to generate social instability of growing concern to civil and military planners.

Vörösmarty, C., McIntyre, P., Gessner, M., Dudgeon, D., Prusevich, A., Green, P., Glidden, S., Bunn, S., Sullivan, C., Liermann, C., & Davies, P. (2010). Global threats to human water security and river biodiversity Nature, 467 (7315), 555-561 DOI: 10.1038/nature09440

ResearchBlogging.org

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Photo credit: suburbanbloke

Posted in biodiversity science, climate adaptation, climate change science, risk analysis, water | No Comments »

Transfer of transgenic crop toxins to aquatic ecosystems potentially widespread in the industrial Corn Belt of the U.S.

Monday, September 27th, 2010

Genetically modified organisms (GMOs) are back in the news.  A few days ago, NPR featured a couple of blog posts (here and here) considering whether the new GMO “supersized” salmon will be harmful to aquatic ecosystems.

A concern with GMOs is that—like the early adoption of pesticides—potential risks are being borne by the environment and consumers as we experiment with new species.  There’s a lot of potential for GMOs, and I hope that they all end up being harmless.  But there are potential downsides too that we are not able to assess very well at this point.  And we may be creating problems that we are not even aware of yet.

As more data come in, it’s not always an encouraging outlook.  A couple of recent examples:

Case #1: We saw a few months ago how weeds that were supposed to be eliminated by the agricultural herbicide, Roundup, are now evolving resistance to the chemical, meaning that Roundup-ready soybeans and other crops no longer work as designed.

Case #2:  In this week’s Early Edition of the Proceedings of the National Academy of Sciences, Jennifer Tank and colleagues examined what happens to transgenic corn residue (old crop parts left on fields that are not harvested).  One of the main transgenic varieties of corn is known as “Bt corn.”  Bt stands for the name of a microbe—Bacillus thuringiensis—that makes a protein toxin that destroys the functioning of guts in some insects.  Scientists have figured out how to move the Bt gene, and hence Bt toxin manufacturing capacity, from the bacteria to corn plants, thereby conferring general insect herbivore resistance to this crop (the main pest being the European corn borer).

This team asked:  What happens when corn stalks, cobs, and leaves end up in streams and rivers throughout the Midwest?  Their answer is eye-opening:

Widespread planting of maize throughout the agricultural Midwest may result in detritus entering adjacent stream ecosystems, and 63% of the 2009 US maize crop was genetically modified to express insecticidal Cry proteins derived from Bacillus thuringiensis. Six months after harvest, we conducted a synoptic survey of 217 stream sites in Indiana to determine the extent of maize detritus and presence of Cry1Ab protein in the stream network. We found that 86% of stream sites contained maize leaves, cobs, husks, and/or stalks in the active stream channel. We also detected Cry1Ab protein in stream-channel maize at 13% of sites and in the water column at 23% of sites. We found that 82% of stream sites were adjacent to maize fields, and Geographical Information Systems analyses indicated that 100% of sites containing Cry1Ab-positive detritus in the active stream channel had maize planted within 500 m during the previous crop year. Maize detritus likely enters streams throughout the Corn Belt; using US Department of Agriculture land cover data, we estimate that 91% of the 256,446 km of streams/rivers in Iowa, Illinois, and Indiana are located within 500 m of a maize field. Maize detritus is common in low-gradient stream channels in northwestern Indiana, and Cry1Ab proteins persist in maize leaves and can be measured in the water column even 6 mo after harvest. Hence, maize detritus, and associated Cry1Ab proteins, are widely distributed and persistent in the headwater streams of a Corn Belt landscape.

Who cares?  Streams and rivers are the breeding grounds to many insect species, including dragonflies, mayflies, and damselflies.  If there are toxins floating in these aquatic ecosystems that are good at killing insects, there is risk of disrupting food webs, including potential changes to bird species as well as many important recreational and sport fish that dine on insects:

Once maize detritus enters stream channels, this carbon source degrades rapidly via a combination of microbial decomposition, physical breakdown, and invertebrate consumption, and that energy may fuel stream food webs. Maize detritus in agricultural streams decomposes in ∼66 d …. Therefore, the material that we found during our synoptic survey had entered these streams relatively recently. Maize detritus is rapidly colonized by stream-dwelling invertebrates, and growth rates of invertebrates feeding on nontransgenic decomposing maize are comparable to those feeding on the deciduous leaf litter commonly found in forested streams

Perhaps this means that the Bt toxins might break down quickly and pose less harm? Doesn’t look like it:

Our data demonstrate that long after harvest, Cry1Ab is present in submerged Bt maize detritus; thus, stream organisms may be exposed to Cry1Ab for several months.

It’s also interesting to learn that low or no-till conservation tillage practices may exacerbate the corn residue inputs because greater material left on fields is susceptible to washing away:

The dried detritus left on fields after harvest, as part of conservation tillage, enters headwater streams as a result of surface runoff and/or wind events occurring throughout the year. During heavy precipitation, overland flow is the likely mechanism transporting this material to stream channels.

It may not even be a matter of leaving less residue; the toxins also appear to be draining through the soils:

Our results from tile drains indicate that tiles may be a mechanism by which Cry1Ab leached from detritus on fields or from soils can be transported to streams.
Cry1Ab released from root exudates or decaying maize detritus moves vertically through soils and can be detected at the base of 15-cm-long soil profiles for up to 9 h.

Their conclusion?  An illustration of how little we know at this point:

The question of whether the concentrations of Cry1Ab protein we report in this study have any effects on nontarget organisms merits further study.

Jennifer L. Tank, Emma J. Rosi-Marshall, Todd V. Royer, Matt R. Whiles, Natalie A. Griffiths, Therese C. Frauendorf, and David J. Treering (2010). Occurrence of maize detritus and a transgenic insecticidal protein (Cry1Ab) within the stream network of an agricultural landscape Proceedings of the National Academy of Sciences : 10.1073/pnas.1006925107

ResearchBlogging.org

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Photo credit: snake.eyes

Posted in biodiversity science, food and agriculture, organic, risk analysis | 8 Comments »

The outlook for biodiversity conservation

Saturday, September 11th, 2010

This week’s issue of Science includes a special section on biodiversity.  A review article by Michael Rands and colleagues, Biodiversity Conservation: Challenges Beyond 2010, summarizes the current approaches and challenges for conservation.

Here is an excerpt describing their outlook for the future:

The challenges of addressing the social and behavioral contexts for biodiversity conservation are daunting. We are far from including biodiversity in our conventional measures of well-being, which focus on wealth creation and internationally
recognized estimates of GDP. Although there have been attempts to redefine these (including, for instance, the Human Development Index and green national accounts), the mainstream view of well-being and of national development remains focused on narrowly defined economic growth. Furthermore, the current recession only strengthens the emphasis on growth. The transition to sustainability will not be easy, but it is central to securing a future for biodiversity. Conservation strategies, in concert with other environmental policies, must address seemingly intractable and politically unpalatable issues. In both developed and emerging economies, we need to reduce the carbon and material throughput demanded by current patterns of production and consumption if we are to create viable and democratically acceptable trajectories of contraction and convergence in resource use. In parallel, we must recognize that successful human development agendas are underpinned by functional ecosystems, and by biodiversity. This is the year in which governments, business, and civil society could decide to take seriously the central role of biodiversity in human well-being and quality of life and to invest in securing the sustainable flow of nature’s public goods for present and future generations.

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Brazil: Amazon deforestation rate plunging

Saturday, September 11th, 2010

In a previous post last week, we discussed a new paper in PNAS showing that new land for agriculture during the ’80s and ’90s came at the expense of tropical forests and savannas.

In this week’s issue of Science, Antonio Regalado reports on satellite imagery (able to record land clearing and fires from slash-and-burn agriculture) showing substantial deforestation declines in the Brazilian Amazon since 2004—from a peak of 27,000 km2/year in 2004 to 7,500 km2/year in 2009.

Why the dramatic downturn over the past half decade?

Environment Minister Izabella Teixeira … credited government enforcement efforts, including cutting off loans to those clearing large amounts of forest for cultivation…

Gilberto Câmara, general director of INPE, said that farmers may now be employing smaller conflagrations to escape detection, and the agency reported a large increase in the number of fires last month. He believes a more accurate survey known as Prodes, due out in November, will show a smaller decline. “We are seeing a process of consolidation in the Amazon, with no new frontiers, fewer large scale cuts, and more small fires to expand existing farms,” he says.

Daniel Nepstad, a senior scientist at the Woods Hole Research Center in Massachusetts, says that recent decisions by large food processors and supermarkets not to buy soybeans and beef from newly deforested areas has helped to slow the rate of deforestation. Some landholders may also be conserving forests in hope of receiving carbon credits.

But Nepstad worries that the picture could change for the worse if prices for
agricultural products, depressed because of a sluggish economy, begin to rebound.
“I think the bigger question is, ‘When the prices come up, will Brazil’s government be
able to hold the line?’ ”

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Photo credit: CIAT

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New land for agriculture coming mainly at the expense of tropical ecosystems

Wednesday, September 1st, 2010

There have traditionally been two ways to produce more food for an increasing population:  Convert native ecosystems like forests and grasslands to agricultural fields (what we call “extensification”) or make the yields on existing croplands go up, through the use of things like machinery, fertilizers, irrigation, pesticides, and GMOs (what we call “intensification”).

Historically, these processes have occurred in tandem:  an initial phase of extensification and land clearing followed by development and intensification.  Converting North America’s prairies to corn and wheat in the 19th century is a classic example of the former, whereas 20th-century rise of fossil fuels, and the machines and fertilizer they support, is an example of the latter.

So while it’s not surprising to learn that developing nations in tropical regions are experiencing significant deforestation for food production, as Holly Gibbs and colleagues at Stanford describe in the early edition of the Proceedings of the National Academy of Sciences (citations removed for clarity), it’s important to understand the magnitude of ecosystem change as well as the drivers of change:

This study confirms that rainforests were the primary source for new agricultural land throughout the tropics during the 1980s and 1990s. More than 80% of new agricultural land came from intact and disturbed forests. Although differences occur across the tropical forest belt, the basic pattern is the same: The majority of the land for agricultural and tree plantation expansion comes from forests, woodlands, and savannas, not from previously cleared lands.

Worldwide demand for agricultural products is expected to increase by ∼50% by 2050, and evidence suggests that tropical countries will be called on to meet much of this demand. Consider, for example, that in developed countries the agricultural land area,
including pastures and permanent croplands, decreased by more than 412 million ha (34%) between 1995 and 2007, whereas developing countries saw increases of nearly 400 million ha (17.1%). Moreover, developing countries expanded their permanent croplands by 10.1% during the current decade alone, while permanent cropland areas in developed countries remained generally stable. If the agricultural expansion trends documented here for 1980–2000 persist, we can expect major clearing of intact and disturbed forest to continue and increase across the tropics to help meet swelling demands for food, fodder, and fuel.

Indeed, recent studies confirm that large-scale agro-industrial expansion is the dominant driver of deforestation in this decade, showing that forests fall as commodity markets boom. Rising commodity prices have been implicated in the destruction of Amazonian rainforests for soy production and peat swamp forests for oil palm production in Southeast Asia. Drivers of cropland expansion may impact forests directly through local or regional demand or indirectly through more globalized demand that may occur via market-mediated effects. Although this study does not specifically assess displacement or indirect land use changes, it does highlight the likelihood that intact and degraded forests will be replaced by agricultural land when such changes occur. Regardless of the mechanism, concern continues to mount about the large emissions of carbon dioxide that result when tropical forests are felled and often burned to make room for new agricultural land.

This was more of a land use change analysis, so it didn’t include a lot on the global drivers causing deforestation.  It would be a mistake, for instance, to ascribe all of this change to population growth in these tropical regions or efforts to supply more food to people living there.  Rather, extensification today is a global phenomenon driven by international trade, as the developing world loses native ecosystems to feed other countries.  And destroying forests and peatlands is a major net source of greenhouse gas emissions, so we’re also warming climate as an unintended consequence.

Why not just halt extensification and switch to intensification on existing farmland?  It’s expensive—moreso than simply clearing more land in many cases.  When the demand for cheap food rules the world, forest clearing in poor countries with abundant, cheap land is often what you get.

It should make us all pause considering that the environmental effects of the demand for goods like soy and palm oil by the industrialized world are being externalized to tropical countries.  We are now chopping down tropical forests to make soy burgers, biodiesel, and snack foods.  As Cameron Scott notes, “The Amazon, It’s What’s for Dinner.”

Reference:

H. K. Gibbs, A. S. Ruesch, F. Achard, M. K. Clayton, P. Holmgrene, N. Ramankutty, and J. A. Foley (2010). Tropical forests were the primary sources of new agricultural land in the 1980s and 1990s Proceedings of the National Academy of Sciences

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Posted in biodiversity science, biofuels, food and agriculture, land use, population | 1 Comment »

New analysis of pesticides and bee colony collapse disorder

Friday, March 19th, 2010

European bee populations are on the decline worldwide.   Who cares?  These bees are major pollinators of crops and therefore perform, for free, a vital ecological service worth about $U.S. 14 billion per year.  Not to mention the many other species of non-crop flowering plants that reproduce with the help of insects like this.

The recent kind of decline is specific—only female worker bees disappear—and has been given the name colony collapse disorder (CCD).  Nobody has figured out why this is happening.  The potential list of culprits includes mites, viruses, synthetic chemicals, and other factors.

In an article this week in PLoS ONE, Christopher Mullin and colleagues explore further the potential link between pesticides and CCD.1

Excerpts:

One third of honey bee colonies in the US were lost during each of the last three winters between ’06-’09. This alarming overwinter along with other losses of this primary pollinator, Apis mellifera L., as well as those of native pollinators, has been documented in North America and Europe. The most recent manifestation of this decline, Colony Collapse Disorder (CCD), has led to a significant collaborative effort involving several land grant universities, Departments of Agriculture and the USDA.

We have found 121 different pesticides and metabolites within 887 wax, pollen, bee and associated hive samples. Almost 60% of the 259 wax and 350 pollen samples contained at least one systemic pesticide, and over 47% had both in-hive acaricides fluvalinate and coumaphos, and chlorothalonil, a widely-used fungicide. In bee pollen were found chlorothalonil at levels up to 99 ppm and the insecticides aldicarb, carbaryl, chlorpyrifos and imidacloprid, fungicides boscalid, captan and myclobutanil, and herbicide pendimethalin at 1 ppm levels. Almost all comb and foundation wax samples (98%) were contaminated with up to 204 and 94 ppm, respectively, of fluvalinate and coumaphos, and lower amounts of amitraz degradates and chlorothalonil, with an average of 6 pesticide detections per sample and a high of 39. There were fewer pesticides found in adults and brood except for those linked with bee kills by permethrin (20 ppm) and fipronil (3.1 ppm).

The 98 pesticides and metabolites detected in mixtures up to 214 ppm in bee pollen alone represents a remarkably high level for toxicants in the brood and adult food of this primary pollinator. This represents over half of the maximum individual pesticide incidences ever reported for apiaries. While exposure to many of these neurotoxicants elicits acute and sublethal reductions in honey bee fitness, the effects of these materials in combinations and their direct association with CCD or declining bee health remains to be determined.

The high frequency of multiple pesticides in bee collected pollen and wax indicates that pesticide interactions need thorough investigation before their roles in decreasing bee health can be either supported or refuted. The large number of studies to date, are limited by being done on mostly one compound at a time, as well as using whole colonies where the timing of contaminated pollen intake and its utilization by the colony are difficult to interpret as a causal relationship. Laboratory studies have clearly indicated sublethal impacts on honey bee learning, immune system functioning, and synergism of insecticide toxicity by fungicides, yet combinations of herbicides with fungicides and insecticides in 3 or more component mixtures have not been studied.

The widespread occurrence of multiple residues, some at toxic levels for single compounds, and the lack of any scientific literature on the biological consequences of combinations of pesticides, argues strongly for urgent changes in regulatory policies regarding pesticide registration and monitoring procedures as they relate to pollinator safety. This further calls for emergency funding to address the myriad holes in our scientific understanding of pesticide consequences for pollinators. The relegation of bee toxicity for registered compounds to impact only label warnings, and the underestimation of systemic pesticide hazards to bees in the registration process may well have contributed to widespread pesticide contamination of pollen, the primary food source of our major pollinator. Is risking the $14 billion contribution of pollinators to our food system really worth lack of action?

1Christopher A. Mullin, Maryann Frazier, James L. Frazier, Sara Ashcraft, Roger Simonds, Dennis vanEngelsdorp, Jeffery S. Pettis (2010). High Levels of Miticides and Agrochemicals in North American Apiaries: Implications for Honey Bee Health PLoS ONE

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Posted in biodiversity science, food and agriculture, organic, pollutants, toxics | 2 Comments »

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