Honey Bee Colony Collapse Disorder (CCD) VII: IAPV, Nosema ceranae, and CCD

Is Colony Collapse Disorder (CCD) caused by new or re-emerging pathogens? This is one hypothesis put forward by US researchers in 2007 and two candidates, the Israeli Acute Paralysis Virus (IAPV) and the microsporidian parasite Nosema ceranae, have received the most mention in the press.

I reviewed the available scientific literature to evaluate the weight of scientific evidence for the role of each pathogen in CCD and found that in terms of both the number of scientific papers and their substantial content the weight of evidence supports Nosema ceranae over IAPV as a cause of CCD, at least in Spain. Additionally, recent research does not support IAPV as a cause of CCD, in either the United States or Europe.

However, despite this evidence, there is a knowledge gap in the literature about the role of Nosema ceranae in CCD in the United States, which may arise from early US research focus on IAPV, the later start on research on IAPV relative to Nosema ceranae, or different causes of CCD in Europe and the United States. More experimental research is required to confirm that Nosema ceranae does, or does not, play a role in CCD in North America.

Until then, the current weight of evidence for a cause-effect link between Nosema ceranae and CCD supports the adoption of precautionary bee-keeping practices that account for it.

Background

Soon after colony collapse disorder (CCD) emerged in 2006, US researchers focused on a suite of hypotheses, one of which was that CCD is caused by new or re-emerging pathogens (see here).

In 2007, a paper in journal Science reported that a relatively new virus, the Israeli Acute Paralysis Virus (IAPV), was associated with observed occurrences of CCD, a finding that not only generated a tremendous amount of press coverage (see here), but some international intrigue as well (see here). As recently as this year, US researchers were still discussing of the role of IAPV in CCD in a general science magazine.

Nosema ceranae, while recognized as an emerging threat to honey bees prior to CCD, was quickly dismissed as a candidate pathogen for CCD by the primary US researchers. Little was written in the general press about Nosema ceranae until early in 2009 when it received its own press boost after a paper was published by Spanish researchers which appeared to convincingly connect it to CCD (see here).

The challenge to the layperson following developments in CCD research is keeping such press reports on scientific research results in perspective. Reporters often rely on press releases prepared by research institutions and may let the researchers themselves place their results in context.

While this is an important part of reporting on science, reporters rarely dig deep enough or follow a particular issue long enough to be able to establish the relative importance of a particular paper for the reader, beyond the immediate research being reported. This is especially the case for a topic as significant, complex and long-lasting as CCD; it is difficult for the interested layperson keep abreast of the research initiatives and findings, many of which are not reported upon in the general press.

The purpose of this analysis, then, is to determine the relative weight of evidence for the role of IAPV and Nosema ceranae as causes of CCD by finding and evaluating the peer-reviewed scientific evidence available for each.

Methods

I used Google Scholar to search the peer-reviewed scientific literature for research papers on both IAPV and Nosema ceranae (search is current up to the date of this posting). For each pathogen, I considered both the number of scientific papers published about it, from its first appearance in the literature until the present, and their substantive nature in relation to CCD. That is, for each pathogen, I considered how directly the observational or experimental evidence reported in the papers supported a cause-effect link between it and CCD.

To make the direct case for a cause-effect link between a particular pathogen and CCD, the research had to show that infection by the pathogen in question caused symptoms of CCD:
1) most adult bees have left and failed to return to the hive leaving the queen behind (uncharacteristic of bee behaviour);
2) colony losses are rapid and occur in large numbers; no dead adult bees are found within or near the hive;
3) delayed honey robbing behaviour from nearby colonies and honey predators (highly unusual); and
4) the few adults found within abandoned colonies are often highly infected with multiple pathogens.

Results

Evidence for a Cause-Effect Link between the Israeli Acute Paralysis Virus (IAPV) and CCD

The first published description of IAPV in the scientific literature is in 2007. Maori et al. (2007) report that following unusually high honey bee colony losses in Israel, they isolated IAPV, a virus closely related to two previously known bee viruses, the kashmir bee virus and acute bee paralysis virus.

[Cox-Foster and vanEngelsdorp (2009) write that IAPV was first described in 2004 by Ilan Sela of the Hebrew University of Jerusalem; however, I could not find a published paper to support this. It may be referenced in another paper as a personal communication, or just common knowledge in the bee virus research community. Sela is a co-author of Maori et al. 2007].

That same year, Cox-Foster et al. (2007) published a paper in the journal Science reporting an association between the presence of IAPV and dead colonies exhibiting the symptoms of CCD. This research received much press, but though it showed an association between IAPV and CCD, it did not establish a causal link between them (Anderson and East 2008). For example, CCD could have made the bees susceptible to IAPV infection (Cox-Foster and vanEngelsdorp 2009).

A third IAPV paper published in 2007 reported that the virus had been present in honey bees in the United States for a number of years prior to the onset of CCD (Chen and Evans 2007). So, if IAPV was a cause of CCD, something must have changed to make it more virulent. This ‘something’ could be a new strain arising through genetic mutation, or the arrival of a more virulent strain from outside the US.

Papers relevant to IAPV and CCD that have been published since Cox-Foster et al. (2007) include:
- Palacios et al. (2008): found distinct clusters of the IAPV virus in the United States.
- Blanchard et al. (2008): reported the first detection of IAPV in France, but their results were inconclusive about its relationship to observed colony losses.
- Maori et al. (2009): reported that IAPV can be ‘silenced’ by dsRNA ingestion, suggesting a potential future treatment for the virus.

None of these papers strengthen the support for IAPV as a cause CCD, and recent research weakens the link even further. vanEngelsdorp et al. (2009) report that a replication of the work reported by Cox-Foster et al (2007) did not show IAPV was associated with CCD – that is, they were unable to replicate those earlier results, though they found that the prevalence of other viruses was generally comparable to the prior results.

In summary, the published scientific evidence on IAPV to date does not support the hypothesis that IAPV is a cause of CCD, however, the primary US researchers of CCD remain convinced that a virus of some kind lies at the bottom of the mystery: “The growing consensus among researchers is that multiple factors such as poor nutrition and exposure to pesticides can interact to weaken colonies and make them susceptible to a virus mediated collapse.” (Cox-Foster and vanEngelsdorp 2009)

Evidence for a Cause-Effect Link between Nosema ceranae and CCD

Meanwhile, in Europe there is little or no support for IAPV as a cause of CCD, but lots for Nosema ceranae. There CCD is also called Honey Bee Colony Depopulation Syndrome (HBDS) and research into the role of Nosema ceranae in honey bee colony losses has been going on since before the onset of CCD in the United States, with the pathogen gradually becoming the primary suspect.

Nosema ceranae is a microsporidian (fungal) parasite of the Asian honeybee Apis ceranae that is closely related to Nosema apis, a long known pathogen of the European honeybee Apis mellifera. Nosema ceranae is first mentioned in the scientific literature as a parasite of Apis ceranae in 1996 (see Fries et al. 1996), but not long after that it emerges as a pathogen of Apis mellifera being reported first in Taiwan by Huang et al. (2007) (research submitted for publication in 2005) and then in Spain (Higes et al. 2006).

Since then, research on N. ceranae has steadily accumulated with the publication of at least twenty more papers. For this analysis, I focused on a subset of those papers that describe N. ceranae’s spatial distribution, its pattern of temporal emergence, and the experimental evidence of its role in honey bee colony collapse; however, the citations for the other papers are also included at the end of this article for those interested.

Spatial Distribution of Nosema ceranae:

Nosema ceranae is now widespread throughout the world as a pathogen of Apis mellifera. Klee et al. (2007) summarised its global dispersal as of 2006, when it was present in at least 15 countries across the Americas and Caribbean (Brazil, Martinique, Washington DC), Asia (Vietnam, Taiwan), Europe and Near East (Denmark, Finland, France, Germany, Greece, Italy, Serbia, Spain, Sweden, Switzerland). They attributed its rapid long distance dispersal to the transport of infected honey bees by commercial or hobbyist bee keepers.

Since then, Nosema ceranae has been found in Canada (the provinces of Nova Scotia, New Brunswick and Prince Edward Island) and extended its range in the United States (Minnesota) (Williams et al. 2008). It has also been found in Uruguay (Inverrnizzi et al. 2009), Australia (Giersch et al. 2009) and Hungary (Tapaszti et al. 2009).

Temporal Emergence of Nosema ceranae:

Not only does the scientific literature show that Nosema ceranae has become globally distributed, it also shows that it has been infecting Apis mellifera probably since it was first reported in the literature as a parasite of Apis ceranae. Klee et al. (2007) concluded that N. ceranae had jumped to Apis mellifera ‘within the last decade’ (their paper was submitted for publication in October 2006), a finding consistent with the research of Paxton et al. (2007), who reported that Nosema ceranae had been present in Apis mellifera in Europe since at least 1998.

Where it has become established, N. ceranae has gradually displaced N. apis as the most prevalent nosema infection. Martin-Hernandez et al. (2007) found evidence of Nosema ceranae’s growing severity over time in Europe, with the gradual replacement of N. apis by N. ceranae as the most prevalent nosema infection in in bees samples from Spain, Switzerland, France and Germany. Similar results were found in North America by Chen et al. (2008), who reported that N. ceranae had not only been present there for longer than previously thought (since at least 1995), but that by 2007 it was the primary nosema infection of the honey bees they tested.

Experimental Link between Nosema ceranae and CCD

The rapid spread of Nosema ceranae around the globe and its temporal pattern of emergence and intensification coincided with increasing numbers of colony collapses (e.g., Martin-Hernandez et al 2007). Nevertheless, ‘correlation is not causation’, a saying exemplified by the IAPV case above - and further scientific work would be required to establish the cause-effect link between N. ceranae and CCD.

As Klee et al. (2007) remarked, “Analyses of colonies with and without apparent nosema disease combined with experimental infection trials are needed to determine if there is a causal link between Nosema ceranae and colony collapse.” The scientific research into Nosema ceranae gradually provided strong experimental evidence of a cause-link, at least in Europe. Below is a sketch of the key research findings that establish this connection.

First, Fries et al. (2006) confirmed that Nosema ceranae has become established as a naturally recurring and persistent new infection of European honey bees and could no longer be thought of as a sporadic, exotic infection caused only by the importation of bees or bee products.

Second, experimental infection trials demonstrated that not only was Nosema ceranae able to infect and kill Apis mellifera, it was far more pathogenic than its relative Nosema apis (Higes et al. 2007). In fact, it was soon established that the relative risk of bee depopulation observed in colonies with both Nosema species or N. ceranae only was almost 6 times greater than in colonies without such infections (Martin-Hernandez et al. 2007).

Third, Higes et el. (2007) also described a plausible ‘mechanism of collapse’. They found that bees infected with Nosema ceranae died suddenly after a period of infection, which supported a hypothesis that infected bees die away from the hive while foraging, leading to a steady colony depopulation that would only be detected when a hive (i.e. the queen) could not keep up with the disappearance of foragers in the field (i.e. by laying more eggs and producing worker bees). To an observer, say a commercial beekeeper, this would appear to be a sudden loss and thus one of the key symptoms of CCD – colonies found without adult worker bees and no dead bees near the hive.

Fourth, Higes et al. (2008) showed that natural infection of bee colonies by Nosema ceranae could cause colony collapse. Consistent with the hypothesized ‘mechanism of collapse’ of Higes et al. (2007), they found that signs of colony weakness were not observed until the queen could no longer replace the loss of infected worker bees and that the long period asymptomatic N. ceranae infection helped explain the absence of obvious symptoms until colony collapse occurred.

Importantly, Higes et al. (2008) also showed that Nosema ceranae could be isolated from infected bees, used to infect non-infected colonies, that these colonies subsequently collapsed, and that Nosema ceranae could then be isolated from in bees from those colonies. Theses steps follow Koch’s postulates, a key part of the process for establishing a cause-effect link between a candidate pathogen and a disease. The lack of these steps was a key criticism of the conclusions drawn by Cox-Foster et al. (2007) about the link between IAPV and CCD (e.g., Anderson and East 2008).

Fifth and finally, Higes et al. (2009) reported how Nosema ceranae caused colony collapse in two commercial bee operations, the first such case observed under field conditions. In both cases, analyses supported the conclusion that the observed collapse was due to infection by Nosema ceranae. The researchers searched for and did not find other significant pathogens (e.g., IAPV) or pesticides (e.g., neonicotinoids).

The Weight of Scientific Evidence Favours Nosema ceranae over IAPV as a Cause of CCD

The weight of scientific evidence favours Nosema ceranae over IAPV as a cause of CCD. Not only have more scientific papers been published on Nosema ceranae than IAPV (23 vs. 7), but these papers include a series of substantive papers that experimentally establish a causal link between Nosema ceranae and colony collapse in Europe.

This substantive research shows that Nosema ceranae jumped from Apis ceranae, its natural host, to Apis mellifera sometime in the early to mid-1990’s, that it quickly increased its spatial distribution around the world during the same period of time that Europe and other areas in the world saw increasing instances of colony collapse, that it is now a natural pathogen of Apis mellifera, that it is highly pathogenic to Apis mellifera, that experimental infection of Apis mellifera by Nosema ceranae produces colony collapse exhibiting a key symptom of CCD, that this symptom can be accounted for through a plausible biological ‘mechanism of collapse’, and that natural infections cause colony collapse in commercial beekeeping operations under field conditions in the absence of other suspected causes, such IAPV or pesticides.

No comparable body of research exists for IAPV, and in fact scientific support for IAPV as a cause of CCD in the US has recently waned after vanEngelsdorp et al. 2009 failed to replicate the findings of Cox-Foster et al (2007) – that is, IAPV was not correlated with CCD in this new study.

Thus, based on my two performance measures of number of publications and their substantive content, I conclude that there is a greater weight of scientific evidence for Nosema ceranae as a cause of honey bee colony collapse than for IAPV.

There is No Published Evidence that Nosema ceranae causes CCD in the United States

Yet, a problem remains: while scientific support for IAPV as a cause of CCD has declined since 2007, there is currently no published scientific evidence that Nosema ceranae plays a role in CCD in the United States. This could be for several reasons.

First, the early US research into CCD quickly dismissed Nosema ceranae as a culprit after it was not detected at levels considered high enough to cause colony collapse (see Russell 2007 and also Cox-Foster et al. 2007). This could explain why, in their recent Scientific American article about CCD, Cox-Foster and vanEngelsdorp (2009) do not specifically mention of N. ceranae at all, just that two nosema species were found and dismissed as a possible cause of CCD.

This early dismissal of Nosema ceranae by senior and influential researchers may have biased the direction of research and research funding in the US away from N. ceranae and towards IAPV. This may change with more recent US research that found that in some cases N. ceranae was present in levels high enough to cause colony collapse (van Engelsdorp et al. 2009).

Additionally, perhaps the time has come for greater collaboration between European and US scientists on the potential role of Nosema ceranae in North American cases of CCD. It would at least be useful to rule it out through direct experimentation, rather than indirectly through correlation, especially given the substantial scientific support for its role in CCD in Europe.

Second, research on Nosema ceranae in Europe has been going on a lot longer than research on CCD and IAPV in particular, in the North America. The first papers suggesting a role for N. ceranae in colony collapse were published in 2006, based on research completed in 2005 or earlier, while IAPV emerged as a pathogen of concern in 2007. Based on the publication pattern observed for N. ceranae ( 1 paper in 1996, 2 papers in 2006, 5 papers in 2007, 6 papers in 2008, and 8 papers in 2009) perhaps we can expect more substantive papers on the link between IAPV, or some other virus, and CCD over the next few years.

For example, in their recent article in the popular science magazine Scientific American, Cox-Foster and vanEngelsdorp (2009) describe an experiment in which honey bees were experimentally infected with IAPV and then exhibited symptoms consistent with CCD 1-2 weeks later. While this is consistent with the hypothesis that that IAPV causes CCD, they also observed colonies infected with IAPV that did not collapse, and in fact, some of them even managed to rid themselves of the virus. (While this information is interesting, it was not reported in a peer-reviewed journal, thus I did not consider it in the weight of evidence analysis.)

Third, it is important to remember that CCD is not a ‘thing’, but a collection of symptoms. It is possible these symptoms may arise from multiple causes and that CCD in North America may result from a different set of factors than colony collapse in Europe. This ‘multiple factor’ hypothesis is also one of the contenders brought forward during the early days of CCD, and as noted earlier, seems to be where some US researchers are beginning to focus.

In the meantime, the overwhelming weight of scientific evidence for the cause-effect link between Nosema ceranae and colony collapse in Europe, as well as the presence of N. ceranae in North America, supports the adoption of precautionary beekeeping practices. In fact, some professional beekeepers already manage their operations under the assumption that N. ceranae is the primary culprit in colony collapse (Vass 2009).

Next post CCD post: Pesticides and CCD. Cheers.

References for This Post:

Anderson, D. and I.J. East. 2008. The Latest Buzz About Colony Collapse Disorder. Science 8 February 2008: 724c-725c. Letter in response to Cox-Foster et al. 2007.

Blanchard P, Schurr F, Celle O, Cougoule N, Drajnudel P, Thiéry R, Faucon JP, Ribière M. 2008. First detection of Israeli acute paralysis virus (IAPV) in France, a dicistrovirus affecting honeybees (Apis mellifera). Journal of Invertebrate Pathology. July 30, 2008 online

CBC news (April 22, 2009). ``Parasite behind European honeybee colony collapse, researchers say`` (about the Higes et al 2009 paper below)

Cox-Foster, D. and D. vanEngelsdorp. (April 2009). Saving the Honeybee. Scientific American Magazine. See this link – online version: Solving the Mystery of the Vanishing Bees

Cox-Foster, D.L., S. Conlan, E.C. Holmes, G. Palacios, J.D. Evans, N.A. Moran, P. Quan, T. Briese, M. Hornig, D.M. Geiser, V. Martinson, D. vanEngelsdorp, A.L. Kalkstein, A. Drysdale, J. Hui, J. Zhai, L. Cui, S.K. Hutchison, J.F. Simons, M. Egholm, J.S. Pettis and W.I. Lipkin. 2007. A Metagenomic Survey of Microbes in Honey Bee Colony Collapse Disorder. Science 318 (5848): 283 – 287.

Chen, Yanping and J.D. Evans 2007. Historical Presence of Israeli Acute Paralysis Virus in the United States. American Bee Journal (here too)

Chen, Y., J.D. Evans, I.B. Smith and J.S. Pettis. 2008. Nosema ceranae is a long-present and wide-spread microsporidian infection of the European honey bee (Apis mellifera) in the United States. Journal of Invertebrate Pathology 97(2): 186-188.

Fries I., R. Martin, A. Meana, P. Garcia-Palencia, M. Higes. 2006. Natural infections of Nosema ceranae in European honey bees. J Apicult Res 45: 230–233.

Fries, I., F. Feng, A. da Silva, S.B. Slemenda, N.J. Pieniazek. 1996. Nosema ceranae n. sp. (Microsporidia, Nosematidae), Morphological and Molecular Characterization of a Microsporidian Parasite of the Asian Honey bee Apis cerana (Hymenoptera, Apidae). European Journal of Protistology, 32(3): 356-365.

Giersch, T., T. Berg, F. Galea and M. Hornitzky. 2009. Nosema ceranae infects honey bees (Apis mellifera) and contaminates honey in Australia. Apidologie 40 (2009) 117-123

Higes, M., R. Martín-Hernández, E. Garrido-Bailón, A.V. González-Porto, P. García-Palencia, A.Meana, M.J. del Nozal, R. Mayo and J.L. Bernal. 2009. Honeybee colony collapse due to Nosema ceranae in professional apiaries. Environmental Microbiology Reports Volume 1 Issue 2, Pages 110 – 113, Published Online: 16 Feb 2009.

Higes, M., Raquel Martín-Hernández, Cristina Botías, Encarna Garrido Bailón, Amelia V. González-Porto, Laura Barrios, M. Jesús del Nozal, José L. Bernal, Juan J. Jiménez, Pilar García Palencia and Aránzazu Meana. 2008. How natural infection by Nosema ceranae causes honeybee colony collapse. Environmental Microbiology, doi:10.1111/j.1462-2920.2008.01687.x

Higes, M., P. García-Palencia, R. Martín-Hernández and A. Meana. 2007. Experimental infection of Apis mellifera honeybees with Nosema ceranae (Microsporidia). Journal of Invertebrate Pathology 94(3), March 2007, Pages 211-217

Higes, M., R. Martína and A. Meana. 2006. Nosema ceranae, a new microsporidian parasite in honeybees in Europe. Journal of Invertebrate Pathology 92(2): 93-95, June 2006. doi:10.1016/j.jip.2006.02.005

Huang, W., J. Jiang, Y. Chen and C. Wang. 2007. A Nosema ceranae isolate from the honeybee Apis mellifera. Apidologie 38 (2007) 30-37, DOI: 10.1051/apido:2006054

Invernizzi, C. , C. Abud, I.H. Tomasco, J. Harriet, G. Ramallo, J. Campá, H. Katz, G. Gardiol and Y. Mendoza. 2009. Presence of Nosema ceranae in honeybees (Apis mellifera) in Uruguay. Journal of Invertebrate Pathology, 101(2): 150-153, June 2009.

Klee, J., A.M. Besana, E. Genersch, S. Gisder, A. Nanetti, D.Q. Tam, T.X. Chinh, F. Puerta, J.M. Ruz, P. Kryger, D. Message, F. Hatjina, S. Korpela, I. Fries and R.J. Paxton. 2007. Widespread dispersal of the microsporidian Nosema ceranae, an emergent pathogen of the western honey bee, Apis mellifera. Journal of Invertebrate Pathology Volume 96, Issue 1, September 2007, Pages 1-10

Maori, E., N. Paldi, S. Shafir, H. Kalev, E. Tsur, E. Glick and I. Sela. 2009. IAPV, a bee-affecting virus associated with Colony Collapse Disorder can be silenced by dsRNA ingestion. Insect Molecular Biology 18(1): 55 – 60, Published Online: 19 Jan 2009.

Maori, E., S. Lavi, R. Mozes-Koch, Y. Gantman, Y. Peretz, O. Edelbaum, E. Tanne and I. Sela. 2007. Isolation and characterization of Israeli acute paralysis virus, a dicistrovirus affecting honeybees in Israel: evidence for diversity due to intra- and inter-species recombination. J Gen Virol 88 (2007), 3428-3438; DOI 10.1099/vir.0.83284-0.

Martín-Hernández, R., A. Meana, L. Prieto, A.M. Salvador, E. Garrido-Bailón and M. Higes. 2007. Outcome of Colonization of Apis mellifera by Nosema ceranae. Applied and Environmental Microbiology, 73(20): 6331-6338

Paxton, R.J., J. Klee, S. Korpela and I. Fries. 2007. Nosema ceranae has infected Apis mellifera in Europe since at least 1998 and may be more virulent than Nosema apis. Apidologie 38:558-565, DOI: 10.1051/apido:2007037.

Palacios, G. et al. 2008. Genetic Analysis of Israel Acute Paralysis Virus: Distinct Clusters Are Circulating in the United States. Journal of Virology, July 2008, p. 6209-6217, Vol. 82, No. 13 doi:10.1128/JVI.00251-08

Russell, S. (April 25, 2007). “UCSF scientist tracks down suspect in honeybee deaths” San Francisco Chronicle

Tapaszti, Z., P. Forgách, C. Kővágó, L. Békési, T. Bakonyi, M. Rusvai. 2009. First detection and dominance of Nosema ceranae in Hungarian honeybee colonies. Acta Veterinaria Hungarica 57(3): 383-388, September 2009, DOI 10.1556/AVet.57.2009.3.4. Online Date Monday, July 27, 2009

vanEngelsdorp, D., J.D. Evans, C. Saegerman, C. Mullin, E. Haubruge, B.K. Nguyen, M. Frazier, J. Frazier, D. Cox-Foster, Y. Chen, R. Underwood, D.R. Tarpy, J.S. Pettis. 2009. Colony Collapse Disorder: A Descriptive Study. PLoS ONE 4(8): e6481. doi:10.1371/journal.pone.0006481 (Received: March 6, 2009; Accepted: June 29, 2009; Published: August 3, 2009)

Vass, Keith. (July 20, 2009). Bees are back as scientists uncover cause of colony collapse disorder. Saanich News.

Williams, G.R., A.B.A. Shafer, R.E.L. Rogers, D. Shutler and D.T. Stewart. 2008a. First detection of Nosema ceranae, a microsporidian parasite of European honey bees (Apis mellifera), in Canada and central USA. Journal of Invertebrate Pathology 97(2): 189-192 (February 2008), doi:10.1016/j.jip.2007.08.005.

Other IAPV and Nosema ceranae references of interest:

Antúnez, K., R. Martín-Hernández, L. Prieto, A. Meana, P. Zunino and M. Higes. 2009. Immune suppression in the honey bee (Apis mellifera) following infection by Nosema ceranae (Microsporidia). Environmental Microbiology, doi:10.1111/j.1462-2920.2009.01953.x

Cornman, R.S., Y.P. Chen, M.C. Schatz, C. Street, Y. Zhao, B. Desany, M. Egholm, S. Hutchison, J.S.
Pettis, W.I. Lipkin and J.D. Evans. 2009. Genomic Analyses of the Microsporidian Nosema ceranae, an Emergent Pathogen of Honey Bees. PLoS Pathog. 2009 June; 5(6): e1000466. Published online 2009 June 5. doi: 10.1371/journal.ppat.1000466.

Hayley, J. (July 19, 2007). Asian Parasite Killing Western Bees. Planet Ark.

M. Higes, R. Martín-Hernández, P. García-Palencia, P. Marín and A. Meana. 2009. Horizontal transmission of Nosema ceranae (Microsporidia) from worker honeybees to queens (Apis mellifera). Environmental Microbiology Reports, doi:10.1111/j.1758-2229.2009.00052.x.

Higes, M., Raquel Martı´n-Herna´ndez, Encarna Garrido-Bailo´n, Pilar Garcı´a-Palencia, Ara´nzazu Meana. 2008. Detection of infective Nosema ceranae (Microsporidia) spores in corbicular pollen of forager honeybees. Journal of Invertebrate Pathology 97 (2008) 76–78.

Maori, E., Tanne, E. & Sela, I. 2007. Reciprocal sequence exchange between non-retro viruses and hosts leading to the appearance of new host phenotypes. Virology 362, 342–349. {cited by Cox-Foster et al 2007 as paper that says IAPV first reported in 2004}

Maori, E., E. Tanne and I. Sela. 2007. Corrigendum to “Reciprocal sequence exchange between non-retro viruses and hosts leading to the appearance of new host phenotypes” Virology 362: 342–349. Virology 368(1), 10 November 2007, Page 218.

Mayack, C. and D. Naug. 2009. Energetic stress in the honeybee Apis mellifera from Nosema ceranae infection. Journal of Invertebrate Pathology 100(3): 185-188.

Pajuelo, A.G., C. Torres, F.J.O. Bermejo. 2008. Colony losses: A double blind trial on the influence of supplementary protein nutrition and preventative treatment with fumagillin against Nosema ceranae. J Apicult Res 47: 84–86.

Williams, G. R., Michelle A. Sampson, Dave Shutler and Richard E.L. Rogers. 2008. Does fumagillin control the recently detected invasive parasite Nosema ceranae in western honey bees (Apis mellifera)? Journal of Invertebrate Pathology Volume 99, Issue 3, November 2008, Pages 342-344 doi:10.1016/j.jip.2008.04.005

“The copyright of the article ‘Honey Bee Colony Collapse Disorder (CCD) VII: IAPV, Nosema ceranae, and CCD’ on ‘What’s Your Ecotype?’ is owned by Ian Parnell. Permission to republish ‘Honey Bee Colony Collapse Disorder (CCD) VII: IAPV, Nosema ceranae, and CCD’ in print or online must be granted by the author in writing.”

Previous posts about CCD:

Honey Bee Colony Collapse Disorder (CCD) I: Should we really be surprised? (May 28, 2007)

Honey Bee Colony Collapse Disorder (CCD) II: What’s causing it? (May 30, 2007)

Green Grazing: Water, Flying Food, Ground-level Ozone, Farmland Biodiversity and Colony Collapse Disorder (July 28, 2007)

Green Grazing: SUDS, Biodiversity Stuff, More About Bees, African Agriculture, and Satellite Fish (August 2, 2007)

Honey Bee Colony Collapse Disorder (CCD) III: The Power of the Press Release (September 28, 2007)

Honey bee Colony Collapse Disorder (CCD) IV: IAPV, CCD, Australian Bees and the Silence of the Press (March 27, 2008)

Honey Bee Colony Collapse Disorder (CCD) V: Trends in Reporting and Research (June 12, 2009)

Honey Bee Colony Collapse Disorder (CCD) VI: The Global Status of CCD (July 10, 2009).

Read more!

Honey Bee Colony Collapse Disorder (CCD) VI: The Global Status of CCD

What is the global status of honey bee Colony Collapse Disorder? Where is it occurring? Is it getting better or worse? Is its range increasing, or decreasing? Such questions might seem easy to answer given the worldwide concern about CCD; however, they turned out to be surprisingly difficult to address.

Using Google and Google Scholar, I searched for quantitative data on honey bee colony losses collected in the context of CCD and that was published in peer reviewed journal papers, association magazines, or industry and government reports.

I found little recent information: three consecutive years of surveys of US beekeepers starting in 2006, one industry summary report from Canada for 2008, and one paper reporting the results of a survey of beekeepers from Turkey in 2007, and the proceedings of a recent (March 2009) conference on colony losses.

The questionnaire-based US surveys specifically track the location, timing, and intensity of winter losses of honey bee colonies and one index of CCD-like losses (dead colonies found in spring with few or no adult bees). In the most recent survey conducted over the winter of 2008/09 total losses were 28.6% while overall CCD-like losses were 15%, much lower than the 60% reported for 2007/08. Unfortunately, the first survey, conducted over the winter of 2006/07, did not report an overall percentage of CCD-like losses.

Outside of the US I only found two reports that provided statistics on winter colony losses: a report on Canadian colony losses for 2007/08 (about 35% over all provinces) and a paper reporting the results of a survey of Turkish beekeepers over the winter of 2006/07 (close to 40% overall). Interestingly, neither source attributed the high reported colony losses to CCD.

The dearth of published data on colony losses may soon be over. I found the proceedings of a conference on honey bee colony losses. It summarizes talks by bee researchers from more than thirty, mostly European, countries. For each country, the researchers discuss data on colony losses and suspected causes. A review of the summaries indicates that CCD is not yet prevalent in Europe. Researchers tend to attribute losses to familiar pests and pathogens and poor management practices.

In summary, the patchwork of published quantitative data does not support a cohesive assessment of the global status of CCD, but does allow these answers to my initial questions: CCD still occurs in the US, it seems to be less intense there this year, and it is not occurring in other countries for which data could be found. Cheers.

References for this post:

Canadian Association of Professional Beekeepers. 2008. CAPA Statement on Honey Bees Losses in Canada (Spring 2008) – Final Revision.

COLOSS 2009. Proceedings of the 4th COLOSS Conference Prevention of honeybee COlony LOSSes in the Faculty of Agriculture University of Zagreb Svetosimunska cesta 25 Zagreb, Croatia March 3-4, 2009.

Giray, T., B. Çakmak, L. Aydin, I. Kandemir, A. Inci, D. Oskay, M. Ali Döke, M. Kence and A. Kence. 2007. Preliminary survey results on 2006-2007 colony losses in Turkey. Uludag Bee Journal August 2007, pp 101-107

vanEngelsdorp, D., J. Hayes, Jr., R.M. Underwood, J. Pettis. 2009a. A Survey of Honey Bee Colony Losses in the U.S., Fall 2007 to Spring 2008. PLoS ONE.

vanEngelsdorp D., J. Hayes, and J Pettis. 2009b. Preliminary Results: A Survey of Honey Bee Colonies Losses in the U.S. Between September 2008 and April 2009. Abstract issued by MAAREC (Mid-Atlantic Apiculture Research and Extension Consortium. (May 19, 2009). {Paper to follow later.}

vanEngelsdorp, D., R. Underwood, D. Caron, J. Hayes, Jr. 2007. An Estimate of Managed Colony Losses in the Winter of 2006 - 2007: A Report Commissioned by the Apiary Inspectors of America. American Bee Journal 147 (7) 599-603.

Previous posts about CCD:

Honey Bee Colony Collapse Disorder (CCD) I: Should we really be surprised? (May 28, 2007)

Honey Bee Colony Collapse Disorder (CCD) II: What’s causing it? (May 30, 2007)

Green Grazing: Water, Flying Food, Ground-level Ozone, Farmland Biodiversity and Colony Collapse Disorder (July 28, 2007)

Green Grazing: SUDS, Biodiversity Stuff, More About Bees, African Agriculture, and Satellite Fish (August 2, 2007)

Honey Bee Colony Collapse Disorder (CCD) III: The Power of the Press Release (September 28, 2007)

Honey bee Colony Collapse Disorder (CCD) IV: IAPV, CCD, Australian Bees and the Silence of the Press (March 27, 2008)

Honey Bee Colony Collapse Disorder (CCD) V: Trends in Reporting and Research (June 12, 2009) Read more!

Honey Bee Colony Collapse Disorder (CCD) V: Trends in Reporting and Research

What ever happened to Colony Collapse Disorder? Since the IAPV breakthrough of 2008 the press has been relatively quiet on this subject. The journalistic stampede that accompanied CCD`s emergence in 2006 has calmed down to an occasional stray article, most of which simply rehash what is already known and reported.

This makes sense when you consider that in some cases it appears the press stampede was driven by press releases from scientific organizations: no breakthroughs = no press releases = no news articles. Nevertheless, while there may be no big news, or at least big press releases, when you dig down, you will find that lots of research is being done as science continues its slow steady pursuit of CCD’s cause. Let’s take a look at some numbers.

The observation that CCD is currently not a hot news item is easy to demonstrate. A search on Google’s News Archive using the phrase ‘colony collapse disorder’ on May 18, 2009 yielded these results, reported as ‘search year (total hits)’:

2005 (0),
2006 (4),
2007(1,680),
2008 (1,150),
2009 (202 to May 18, 2009, linear projection to 534 for whole year).

Clearly, the number of news articles about CCD increased steeply from 2005 to a peak in 2007. Over this period, the press became aware of the CCD phenomenon and scrambled to learn and communicate about it. There was much uncertainty and concern about what was going on. Then, as fresh information became scarce, the number of articles declined dramatically in 2008 (down by 60% from 2007). Projecting from the numbers up to the search date, it looks like barring any major breakthrough the numbers will continue to drop in 2009.

On the other hand, the number of scientific review and research papers related to CCD has increased each year since 2005, as shown by a search on Google Scholar. Using Scholar’s advanced search option and searching on the phrase ‘colony collapse disorder’ ‘anywhere in article’, restricted to the ‘Biology, Life Sciences, and Environmental Sciences’ category yielded these results, reported as ‘search year (total hits, number relevant)’:

2005(7, 0),
2006(1, 0),
2007(36, ~ 25 – mostly general articles outlining the current scientific thinking about CCD, that is, the hypotheses about causative factors),
2008(67 hits, almost all reference the phrase CCD somewhere, many are research papers, also moving into discussions about the need for wild pollinators),
2009 (31 hits up to May 18/09, mostly original research on aspects of CCD, e.g., pathogens and pesticides. Liner projection to 81 publications).

No doubt as more CCD research is published, press releases will stimulate period increase in press coverage. In subsequent posts I will explore the largest blips on the CCD radar the IAPV breakthrough, focusing on three areas: 1) the (relatively) current status of CCD in the US and around the world, 2) the relative roles of suspect pathogens (e.g., IAPV and Nosema ceranea) appear to play in CCD, and 3) and the growing focus on the link between certain classes of systemic pesticides and CCD. Cheers.

Previous posts about CCD:

Honey Bee Colony Collapse Disorder (CCD) I: Should we really be surprised? (May 28, 2007)

Honey Bee Colony Collapse Disorder (CCD) II: What’s causing it? (May 30, 2007)

Green Grazing: Water, Flying Food, Ground-level Ozone, Farmland Biodiversity and Colony Collapse Disorder (July 28, 2007)

Green Grazing: SUDS, Biodiversity Stuff, More About Bees, African Agriculture, and Satellite Fish (August 2, 2007)

Honey Bee Colony Collapse Disorder (CCD) III: The Power of the Press Release (September 28, 2007)

Honey bee Colony Collapse Disorder (CCD) IV: IAPV, CCD, Australian Bees and the Silence of the Press (March 27, 2008).

“The copyright of the article ‘Honey Bee Colony Collapse Disorder (CCD) V: Trends in Reporting and Research’ on ‘What’s Your Ecotype?’ is owned by Ian Parnell. Permission to republish ‘Honey Bee Colony Collapse Disorder (CCD) V: Trends in Reporting and Research’ in print or online must be granted by the author in writing.”

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Measuring Environmental Performance: One Number Is Not Enough

In his article ‘Saving the Planet by Numbers’, David MacKay offers the quantitatively minded enviro-skeptic a new energy standard for comparing the relative performance of green actions and technologies to each other and the status quo. (MacKay, David. (April 23, 2009). “Saving the planet by numbers” BBC News website).

Unfortunately, a single measure of environmental performance usually is not enough to tell the whole story. MacKay proposes a new standard for putting, “. . . green lifestyle ideas under the spotlight.” This standard would measure energies in Kilowatt-hours and how fast activities use or produce energy in Kilowatt-hours per day, or some other unit of time or distance. He provides an overview of how this standard might be used to compare activities and technologies for four categories: ‘Simple Individual Actions’ like you might find on green top-ten lists; ‘Transport’; ‘Heating’; and ‘Decentralized Power Generation’.

For example, under the ‘Transport’ category, MacKay reports that the average fossil-fuelled British car outperforms hydrogen vehicles at 80 KWh/100 km versus 254 KWh/100 km, respectively. He also includes the performance of electric vehicles (6-20 KWh/100 Km) noting that “. . . even if electricity comes from traditional fossil-fuel power stations, electric cars are still more efficient than petrol cars.”

Multiple Measures of Environmental Performance Help Us to Assess Trade-offs Between Alternatives

Unfortunately, a single measure of environmental performance doesn’t tell the whole story. For example, MacKay’s single-number energy standard can’t be used to compare the relative performance of the transport options in terms of reduced emissions of carbon dioxide.

Since we are usually interested in more than one thing when we address environmental concerns, looking at multiple performance measures can provide a clearer picture of the relative tradeoffs inherent to alternative options, transportation-related or otherwise.

Comparing PHEV Impacts Using Ground-Level Ozone Production and Carbon Dioxide Emissions

This is illustrated by the multiple performance measure approach taken in a paper I recently reviewed that used simulation modeling to explore the impact of large-scale use of plug-in hybrid electric vehicles (PHEVs) on air quality: it compared both ground-level ozone production and carbon dioxide emissions across a range of alternative PHEV-use scenarios (see here).

Interestingly, not only did the researchers find that the large-scale use of PHEVs reduced ground-level ozone production, the main focus of their study, but also that carbon dioxide emissions were lower too.

The latter result was somewhat counterintuitive since the virtual PHEVs were charged using electricity from coal-fired generating stations, increasing the greenhouse gas emissions of these facilities above baseline conditions.

The reason was that the large-scale replacement of gasoline-powered vehicles with PHEVs drastically reduced total car-related emissions, more than compensating for the increased emissions from the coal-fired stations.

Multiple Performance Measures Can Also Increase Confidence in Results

This result would have been missed by focusing on ground-level ozone alone as a performance measure. Thus, in this case at least, using multiple performance measures helped build a stronger-case for the expanded use of PHEVs in areas with power-grids fed with electricity from fossil-fuelled generating stations.

My intent here is not to detract from MacKay’s proposed energy standard. It looks like a useful tool for comparing the energy performance of green actions and technologies – in conjunction with other measures. But I think it’s important to remember that environmental choices usually consider, explicitly or implicitly, multiple objectives and values. Focusing too narrowly on a single measure of performance leaves us open to wrongly interpreting results and can also preclude the opportunity to learn. Cheers.

References for this post:
MacKay, David. (April 23, 2009). “Saving the planet by numbers” BBC News website.

“The copyright of the article ‘Do Measuring Environmental Performance: One Number Is Not Enough’ on ‘What’s Your Ecotype?’ is owned by Ian Parnell. Permission to republish ‘Measuring Environmental Performance: One Number Is Not Enough’ in print or online must be granted by the author in writing.”
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Washing Our Car With Rain Barrel Water: How Many Buckets?

It rained hard last night and our rain barrel was full by morning. Since the garden was nicely watered, I decided to use some of that dewy fresh rain water to wash our car. I wanted to try out something I'd read about being able to wash a car using only two buckets of water. So, I went to the rain barrel and filled up our one bucket for the soapy water and our battered watering can for rinsing . . . then I went back to the rain barrel the watering can several more times (six I think). Turns out I couldn't wash our car using two buckets of water - either it's too big, or the buckets are too small! In the end, I'm not sure I saved much water over just using a hose with a spray gun, but at least it was rain water that would have gone down the drain otherwise. With a little practice, though, I think I'll be able to get it down to maybe three or four cans. We'll see. Cheers.

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Do Plug-In Hybrid Electric Vehicles (PHEVs) Really Reduce Emissions?

Plug-in Hybrid Electric Vehicles (PHEVs) are touted as a technology for reducing vehicle related emissions of carbon dioxide and other pollutants that affect human health. However, do they really achieve net improvements in emissions or just shift them from cars to power stations? Recent research has addressed this question, focusing specifically on the potential of PHEVs for improving air quality by reducing emissions of the pollutants that lead to increased low-level ozone concentrations.

Low-Level Ozone is Geographically Localized Problem with Health Implications

Unlike the global problem of stratospheric ozone loss (i.e. the ‘ozone hole’), ground-level ozone is a geographically localized problem arising when sunlight reacts with Volatile Organic Carbons (VOC) and nitrous oxides (NOx). These precursor chemicals occur naturally, but their primary source is the internal combustion engine, a source which ensures the chemicals are especially concentrated near urban centres. High concentrations of these chemicals can create high levels of ground-level ozone, which harms not only human health (see here), but also the yield of agricultural crops (see here).

Reducing Vehicle Emissions Can Lower Low-Level Ozone Concentrations

Fortunately, ground-level ozone is potentially easier to control than stratospheric ozone loss since more local control can be exerted over emissions that create it. Since ground-level ozone is produced by a photochemical reaction between sunlight and some of the chemicals found in car exhaust, the intensity of its production varies by season, time of day and geographic location – factors that affect the how much sunshine and meets how much air pollution. For example, ground-level ozone production is greatest in the summer during the morning hours in areas with lots of traffic (e.g. city centres during the morning rush hour).

For this reason, one way to control ground-level ozone levels is by shifting the timing and intensity of vehicle emissions. This can be done, for example, by prohibiting the use of certain equipment (e.g., lawn mowers) at certain times of the day, or by using tolls or fees to reduce how many cars enter city centres (e.g., London, England).

Another way is to reduce emissions at the source and low-emission vehicles, like PHEV’s can also play an important role. However, it is important to evaluate how and how much such technology can contribute to reducing the problem rather than just assuming it will always help. A question of particular importance is what is the impact on air quality and greenhouse gas emissions of transferring emissions in one sector (on-road vehicles) to emissions in another sector (power plants burning fossil fuels)?

Plug-in Hybrid Electric Vehicles (PHEVs) Reduce Vehicle Emissions and Improve Air Quality

In a recent scientific paper, Thompson et al. (2009) analysed the effectiveness of PHEVs for reducing vehicle-related ozone concentrations. They tested the assumption that charging PHEVs at night with the unused base-load electricity of coal-fired generating stations would lower the diffuse daytime emissions of VOCs, NOx’s from cars enough to offset the increased localized emissions of these pollutants at coal-fired generating stations. They also looked for a net decrease in carbon dioxide emissions.

The researchers based their analysis on a real power-grid covering the N.E. US states of Pennsylvania, New Jersey and Maryland (PJM). They calculated that the ‘excess’ power available at night from the grid’s base-load power plants (largely coal-fired) could support the substitution of 20% of the grid area’s car fleet with PHEVs. This corresponded to roughly a 20% reduction in diffuse vehicle-related emissions during the day and a 20% increase in localized power plant emissions due to coal at night.

The Effect of PHEVs on Air Quality was Evaluated Using a Complex Photochemical Model

The researchers evaluated the impact of these relative changes in vehicle and power plant emissions using historic emissions data for a severe pollution event in August of 2002 in the power-grid area in combination with a sophisticated and complex photochemical model. The model was used to predict the movement of emissions over space and time of air pollutants while accounting for factors that affect the concentration and creation of pollutants like weather conditions, chemical reactions under varying conditions, and the deposition chemicals from air to ground.

The analysis considered four scenarios: 1) a “base case” scenario with the same emission pattern as found for the August 2002 event; 2) an emissions scenario based on the full utilization of PHEVs during the day and then charging them at night using electricity from coal-fired power plants; 3) a less optimistic scenario where emission reductions due to PHEV use were only half of scenario 2; and 4) a scenario where only car emissions changed and there was no increase in the night time emissions from coal-fired power plants. This latter scenario represents increased used of pollution controls for coal-fired plants, or the increased use of alternative non-emitting power sources like wind generation.

The model results for scenario 1, the “base case” scenario, were compared to the actual 2002 data to see how well the model performed and were found to be highly comparable. This provided confidence that the results found under the other three scenarios would follow realistic patterns of behaviour. The results for scenarios 2-4 were then compared to the modelled “base case” results and expressed in terms of changes from the “base case” numbers over a suite of performance measures.

Increased Use of PHEVs Decreased Low-Level Ozone Concentrations and Carbon Dioxide Emissions

The overall results showed that shifting emissions from cars to coal-fired power plants had the potential to significantly reduce ozone levels over most of the power grid area. However, there were also ‘disbenefits’, or worsened conditions in some areas, arising due to the complex chemistry of ozone. Nevertheless, the researchers concluded that increased PHEV use could generally reduce ozone concentrations, especially for cases where PHEVs were charged at night using lower or non-emitting power sources (e.g., wind power, or controlled coal combustion).

Additionally, the results confirmed that using the shift in emissions from cars to power plants did not increase overall carbon dioxide emissions. The additional power generation from the coal-fired power plants led to an increase of about 99,610 tons of carbon dioxide emissions for the grid-area, while the decrease in vehicle related emissions from replacing cars with PHEVs was about 122,670 tons. This is a net reduction in carbon dioxide emissions of about 23,000 tons. Given their analytical assumptions, the researchers cautiously concluded that, at the least, the scenarios they evaluated would not lead to an increase in carbon dioxide emissions.

Thompson et al. (2009) is a Rich Source of Information on Air Quality Science and Regulations

The answer to the question posed at the beginning of this post is thus, “Yes, increased use of PHEVs can lead to a net-reduction in the emissions and improve air quality – most of the time.”

However, this paper is a rich resource for several reasons beyond just answering that question. First, it provides references for quantitative data and regulatory information on emissions science. Secondly, it illustrates how computer modeling is used to explore complex large-scale environmental issues, in this case to better understand how and if proposed regulations and technology can improve air quality. Third, the work is presented in a straightforward way that is accessible to readers interested in the science behind sustainability and green technologies, but without expert training in air quality science. Finally, the results emphasize that ‘sustainability’ is a context-dependent concept; achieving it can depend on your specific objectives as well as how, where and when it is measured - when it comes to living sustainably, details matter.

Related posts: Gasoline vs. Electric Cars

Reference for this post:
Thompson, T., M. Webber, and D.T. Allen . 2009. Air quality impacts of using overnight electricity generation to charge plug-in hybrid electric vehicles for daytime use. Environ. Res. Lett. 4 014002 (12pp) doi: 10.1088/1748-9326/4/1/014002

“The copyright of the article ‘Do Plug-In Hybrid Electric Vehicles (PHEVs) Really Reduce Emissions?’ on ‘What’s Your Ecotype?’ is owned by Ian Parnell. Permission to republish ‘Do Plug-In Hybrid Electric Vehicles (PHEVs) Really Reduce Emissions?’ in print or online must be granted by the author in writing.”

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Reemerging: Some Recent Articles

It's been a - long- while since my last post. What can I say, life can get busy. Among the many things I've been doing is writing articles for Suite 101 on varied topics that include:

• adaptive management;
• the value of scientific information;
• statistical power analysis;
• the link between bushmeat hunted in forests and plains of Ghana and its coastal fisheries; and,
• and the link between agricultral fertilizers and ocean dead zones.

A varied list, indeed, but you might find some of these articles interesting. Click 'read more' for the links to these articles. Cheers.

Mar 14, 2009
Adaptive Management: Learning by Doing
Adaptive management structures choices as experiments so resource managers can learn about ecological and socio-economic systems and improve future choices. more...

Mar 14, 2009
Adaptive Management of Sea Lamprey: Using Science to Improve Assessment Methods for Fisheries
Using adaptive management, two scientists evaluated alternative larval lamprey assessment methods and improved the Great Lakes Sea Lamprey management program. more...

Nov 9, 2008
Statistical Power Analysis: Design Powerful Experiments Capable of Detecting Important Effects Statistical power analysis helps design experiments and monitoring programs that protect against Type I and II errors and have high probability of detecting true effects. more...

Nov 8, 2008
Components of Statistical Power: The Four Pieces of the Power Puzzle
Statistical power is a function of sample variance, sample size, the level of statistical significance, and the effect size of interest. more...

Nov 8, 2008
Think About Statistical Power: The Probability of Detecting a True Effect
Before drawing conclusions based on a non-significant hypothesis, test check its statistical power to detect important effects. more...

Nov 2, 2008
Digital Corn: Using Computer Models to Simulate Agricultural Ecosystems
By growing virtual crops with computers, scientists learn how agriculture interacts with the environment at very large scales. more...

Nov 2, 2008
Biofuels and Dead Zones: More Corn-Ethanol Means More Nitrogen Pollution
The unexpected impact of increased corn-ethanol production on a coastal ecosystem illustrates the challenge of creating sustainable solutions to environmental problems. more...

Sep 4, 2008
'Dead Zones' and Climate Change: Hypoxia in Coastal Ecosystems May Increase As Oceans Warm
Low-oxygen 'dead zones' caused by nutrient pollution are spreading through coastal ecosystems worldwide. Climate change may make this serious environmental problem worse. more...

Nov 8, 2008
Bushmeat Links Land and Sea: How Fluctuations in Ocean Fisheries Can Affect Wildlife Conservation
In Ghana, when the catch from ocean fisheries declines, people eat more 'bushmeat', increasing the hunting pressure on inland wildlife populations. more...

Nov 2, 2008
Assessing Corn-Ethanol's Impacts: Modeling Corn-Ethanol’s Impact on Nitrogen Pollution
Ecosystem modeling is a valuable tool for assessing conflicts between environmental policies, quantifying consequences, and making trade-offs clear. more...

Sep 12, 2008
The Value of Information: Better Science in Natural Resource Management Comes at a Cost
Is better science always worth it? Environmental managers can assess if better science helps achieve broader management goals by considering its 'Value of Information'. more...

Aug 25, 2008
Agriculture Impacts Oceans: Runoff of Agricultural Fertilizers Pollutes Coastal Ecosystems
Agricultural fertilizers pollute coastal ecosystems with excess nutrients, creating hypoxic 'dead zones' that reduce habitat, lower biodiversity and impact fisheries. more...

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