Williams, N., Lundholm, J., & MacIvor, J. (2014). Do green roofs help urban biodiversity conservation? Journal of Applied Ecology DOI: 10.1111/1365-2664.12333
Friday, September 12, 2014
Do green roofs enhance urban conservation?
Williams, N., Lundholm, J., & MacIvor, J. (2014). Do green roofs help urban biodiversity conservation? Journal of Applied Ecology DOI: 10.1111/1365-2664.12333
Thursday, April 24, 2014
Data merging: are we moving forward or dealing with Frankenstein's monster
Wednesday, November 6, 2013
Community structure - what are we missing?
The connection between models, community structure and metrics. |
Part of the problem is that for a long time, the default focus was on what types of interactions structured communities (environment, competition, predation, mutualisms), and niches were assumed to be necessarily driving community structure. The type of measurements and metrics used reflected this search for niches (e.g. comparing environmental gradients with community structure). Many quantitative metrics may tell you something about how community structure relates to different variables (spatial, environment, biotic) and how much variation is still unexplained. The consideration that niches might not always be important eventually led ecologists to compare patterns in community structure to random, null, or neutral expectations. As a result, in the simplest cases the answers to questions about community structure and niches are binary – different from random (niches matter), or not. Looking for complex patterns predicted by models-for example, the relative contribution of niche based and neutral processes to community structure-is difficult using common metrics of community structure (although there are some papers that do a good job of this).
It is interesting that this problem of disconnection between theoretical models of community structure and community structure metrics received the most attention through criticisms of phylogenetic metrics of diversity. There, patterns of over- and under-dispersion were criticized for not being the necessary outcome from models of competition or environmental filtering (i.e. Mayfield and Levine 2010). While those criticisms were mostly fair, they are equally deserved in most studies of species diversity, where patterns in ordinations or beta-diversity are frequently used to infer mechanisms. In contrast, one of the best approaches thus far to integrating model predictions for community structure with metrics of community structure are null models. Though they differ greatly in ecological realism and complexity, null models suggest expected community structure or metric values if none of the expected processes are structuring a community.
One of the greatest failings of the top-down approach is that recognizing patterns outside of the expected, such as those that include stochasticity or a combination of different processes, or the effects of history, is nearly impossible. Models that can incorporate these complexities provide little suggestion of how the patterns we can easily record in communities might reflect complex structuring processes. Ecological research is limited by the poor connection between both top-down and bottom-up approaches and its vague definition of community structure. Patterns more complicated than those that the top-down approach searches for are likely being missed, while relations between models and metrics (or development of new metrics) aren’t considered often enough. One solution might be to more meaningfully define community structure, perhaps as the association (or lack thereof) between the combination of species present in a community and the combination of abiotic and/or biotic processes present. This association is generally compared to an association between species and processes that might arise from random effects alone. The difference is that structure shouldn’t be considered separately from the processes that produce it, and the connections should be explicitly rather than implicitly made.
Monday, October 7, 2013
Why greater diversity – even of parasites – might decrease infections
(Host competence - the tendency of host species to become infected and maintain infection.)
With this in mind, a new paper from Pieter Johnson and colleagues attempts to combine research into the effects of both parasite and host diversity on disease. Two possible hypotheses predict the effect of diversity on disease transmission: the ‘dilution effect’ suggests that the presence of multiple hosts should decrease transmission risk, if the result of additional species is a decline in community competence. It is also hypothesized, somewhat contradictorily, that increased host diversity should support a greater variety of parasites, and parasite life cycles. Both these hypotheses take a host-centric view: understanding how changes in host diversity alter disease risk also requires that we understand how changes in parasite diversity affect disease transmission.
Mutations caused by Ribeiroia infection. From:http://www.nature.com/scitable/knowledge/library/ecological-consequences-of-parasitism-13255694 |
From Johnson et al. 2013 PNAS. Results of field observations. |
From Johnson et al. 2013 PNAS. Results of the microcosm and mesocosm experiments, showing the effects of host and parasite diversity on transmission. |
There are a number of possibilities for why both host and parasite communities alter parasite transmission success. If host diversity changes the susceptibility of the community to infection (i.e. as diversity increases, the number of low competence/susceptible species increases) then low-competence hosts could act as sinks for parasite infections. Increases in parasite diversity could result in inter-parasite competition and interactions via host immunity.
One future step will be to move beyond simple measurements of species richness to understanding how species identity or characteristics are tied to the putative mechanisms. For example, how do communities of host species vary from low to high diversity sites? Do sites in fact tend to assemble with increasing numbers of low competence host species? The implications are also of interest to other types of studies of community ecology – after all, host-parasite interactions are not very different from predator-prey interactions, and similarly, despite knowing that interactions are complex and involve multiple species, we tend to focus on two or three species examples.
Monday, February 11, 2013
The birds and the bees and the microbes
"When we try to pick out anything by itself, we find it hitched to everything else in the Universe."- John Muir
You can’t help but marvel at the complexity of ecology, at the intricacy and multiplicity of species interactions. But this complexity is also problematic. For many ecologists, it becomes necessary to focus on a single type of interaction, or on interactions limited to only a few species. But real ecological systems are hardly ever limited to a single important process. They might include competition, mutualism, facilitation, predation, environmental constraints and fluctuations, additive and interactive effects, nonlinearities, thresholds and emergent properties. Can knowledge of omplexity emerge from simplicity? Can simplicity emerge from complexity? These are important and longstanding questions in ecology, the focus of some of our smartest minds. We may not have the answer yet, but if nothing else, it is helpful when experimental work in community ecology attempts to explore multiple interactions.
For example, some of the work from Tadashi Fukami’s lab is focused on how communities of microorganisms (yeast and bacteria species) assemble in Mimulus aurantiacus nectar. In the past, this work has focused particularly on priority effects and resource competition, which plays an important role in structuring these communities. While past work has suggested the importance of pollinators as a dispersal vector for microorganisms, fascinating new work suggests that microbial communities have important effects on pollinators and their mutualistic interactions with the host plant as well.
Vannette et al. (2013) focused on the effects of the two most abundant species in Mimulus nectar, Gluconobacter sp., an acid-producing bacteria, and Metschnikowia reukaufii, a yeast. They then looked at three related questions – how do nectar microbes affect nectar chemistry, how do they affect nectar removal by hummingbird pollinators, and how to they affect pollination success and seed set. Basically, do nectar microbes disrupt important mutualistic interactions between the plant and their pollinators, or are their effects neutral?
This is where the story becomes interesting. Both types of microbes altered nectar chemistry, but in different ways. The bacteria acidified the nectar (to ~ pH 2.0) far more than the yeast species, and tended to also reduce the sugar content of the nectar far more than the yeast. Hypothesizing that these changes could ultimately affect pollinator preference, the authors then filled artificial flowers with nectar containing either the bacteria, yeast, or no microbes. Half of these flowers were bagged to prevent hummingbird access. Compared to the bagged controls, flowers with bacteria-inoculated nectar had less nectar removed than either yeast-inoculated or sterile nectar. It appeared that nectar removal was related to the changes in chemistry driven by bacterial growth in the nectar. Finally, the authors looked pollination success in relation to microbial inoculation. Flowers inoculated with bacteria did indeed have less pollination success (measured as the number of stigmas closed) and had decreased seed numbers. Microbial communities were not isolated from the ecology of the plant.
Perhaps none of this is that surprising – hummingbirds are intelligent and will preferentially feed, and pollinator choice is important for plant fitness. However, these bacteria and yeast species are specialized for growth in the hypertonic nectar environment and their continued presence in the ecosystem depends on dispersal from one flower to the next before their host flower dies. The transient nature of this nectar habitat suggests that obtaining a dispersal vector should be important. The fact that Gluconobacter alters nectar chemistry in a way which negatively affects their likelihood of movement to other patches suggests an interesting paradox and a complicated relationship between plants, their nectar microbes, and pollinators. Gluconobacter species growing in Mimulus flowers produce acidifying H+ ions and reduce sugar concentrations in nectar – this increases their likelihood of winning competitive interactions with other microbes in the nectar, which should select for the maintenance of acidifying, sugar-reducing characteristics. But on the other hand, these characteristics reduce the likelihood of being transported to new flowers and persisting in the metacommunity. Further, these pollinator-decreasing characteristics may result in selection by the Mimulus plants for nectar compounds that reduce microbial contamination. So understanding competitive interactions in microbial communities, or understanding pollinator-plant interactions, or understanding pollinator-microbial interactions on their own might be inadequate to understand the important ecological and evolutionary processes structuring the entire system.
Given that the question of simplicity vs. complexity is still so difficult and at least for me, uncertain, I would hesitate to draw a general conclusion about whether this is the kind of work all community ecologists should strive for. But it seems that recognizing ecological and evolutionary context is key, whether you work with Arabidopsis, microcosms, or tropical forests.
Tuesday, October 30, 2012
The contrasting effects of habitat area and heterogeneity on diversity
Allouche, O., Kalyuzhny, M., Moreno-Rueda, G., Pizarro, M., & Kadmon, R. (2012). Area-heterogeneity tradeoff and the diversity of ecological communities Proceedings of the National Academy of Sciences, 109 (43), 17495-17500 DOI: 10.1073/pnas.1208652109
Wednesday, August 22, 2012
Justifying assumptions: tests of seed size/mass tradeoffs
Monday, May 30, 2011
Nature’s little blue pill
A few weeks ago, Bradley Cardinale published a study in which he tested the effects of algal biodiversity on water quality in streams. It’s a pretty classic diversity-function experiment; lots of artificial streams with different numbers of species of algae in them, and he measured productivity and nitrogen uptake. As is usually the case, the more species he put in each stream, the more these ecosystem functions increased.
But Cardinale did something else in this experiment that has never been done before, at least not on this scale. He added extra niche opportunities to some of the streams, so that they offered multiple different habitats for algae. He did this by introducing heterogeneity through flow and disturbance manipulations.
Figures from Cardinale 2011, Nature. a and b are the heterogeneous streams, d and e are the homogeneous ones.
You might be familiar with that saturating response curve that is typical of so many diversity-function experiments. It starts off with large increases in ecosystem functioning as species are added to communities, and then it levels off so that as additional species are added, they only increase ecosystem functioning by small amounts (figures d and e). The theory behind this is that there are only so many niches in an environment, and as more and more species are added some of them become redundant.
Well when Cardinale threw those extra habitats into his artificial streams, that floppy old saturating curve sprang up like a regressional jack-in-the-box (figures a and b).
What happened was the homogeneous streams became dominated by just a single species that was well adapted to that environment. The heterogeneous streams allowed different species to coexist and this let them make more efficient use of the resources in those streams.
This is a major finding for a few reasons. First, it confirms that one of the main mechanisms behind diversity-function relationships is niche partitioning. I’ve said in the past that knowledge of these mechanisms is sorely needed. Second, it links coexistence theory to ecosystem functioning, two fields that are closely related but often disconnected.
Finally, it means that biodiversity is even more valuable than we had previously thought. The natural world doesn’t contain very many homogeneous streams; it’s a complicated place. The real world is probably better represented by figures a and b than by figures d and e. So while controlled experiments have shown that some species are redundant for ecosystem functioning, there is no evidence here for any redundancy in more natural settings.
This paper also underlines the fact that these studies need to be done in nature as opposed to labs. Cardinale was able to simulate nature fairly realistically because he was using algae. That’s harder to do with more complex organisms. It’s difficult to recreate environmental heterogeneity in artificial ecosystems, and if ecosystem functioning depends on both biodiversity and heterogeneity, then it’s time to take this research outside. Manipulative field studies are a good start, but completely natural settings will probably reveal more of the true story.
So although it’s very common for artificial communities to suffer from Ecological Dysfunction, there is no reason that they can’t enjoy a healthy relationship with biodiversity like any other community. All they need is a little heterogeneity to spice things up and put that spring back in their step.
Andy Hector has written an excellent perspective on the study. I recommend reading it, particularly if you don’t want to read the entire original article.
Friday, April 15, 2011
The bellybutton, biodiversity reserve of the body
Although less recognized--and less glamourous--than most biodiversity hotspots, the human bellybutton harbours it own diverse collection of species, and these species tell us something about ourselves. That's the premise behind the Belly Button Biodiversity Project, which is getting some press for its large-scale sampling of bellybutton bacteria. For interesting discussion about where the data could lead, see Rob Dunn's (one of the researchers) website. His post, including the comments, hints at how much there is to learn about the ecology of human bacteria.
Update: Rob Dunn has now published a book "The Wild Life of Our Bodies", telling more stories of our changing relationships with other species.
Saturday, April 2, 2011
White-nose syndrome and wind turbines: why biodiversity matters
Linking ecosystem services to economic benefits is a vital step in connecting ecological research to policy and political action. The UN Environmental Programme’s The Economics of Ecosystems and Biodiversity (TEEB) initiative represents a concerted effort to draw attention to the economic benefits of biodiversity and cost of ecosystem degradation, and to bring together scientists, economists and policy-makers.
Accordingly, Boyles et al. (Nature, 2011) paint a troubling picture about the value of economic benefits that insectivorous bats provide to the North American economy, and the degree of extinction risk they currently face. The authors point out that bats are “among the most overlooked, yet economically important, non-domesticated animals in North America”, and their loss would cost North Americans more than 3.7 billion dollars/year. Given rapid declines in populations due to white-nose syndrome (over 1 million bats killed) and wind turbine fatalities (projected to reach up to 30,000-100,000 fatalities/year as wind turbine installations increase), the authors suggest action can't wait.
Hopefully using the universal language of money helps translate scientific knowledge into political action. After all, bats are only one group of species: imagine the true cost of current rates of biodiversity loss and ecosystem destruction, from the smallest microorganism to the largest megafauna. The total must be staggering. And so, it seems, is the scale of action required to halt this decline.
Tuesday, January 25, 2011
Trend in ecology, 2010
For the sake of curiosity, I've compiled the top keywords from ecology publications in 2010. Obviously there are many covariates, but it should come as no surprise that the top words were "biodiversity" (667 times), "climate change" (293), and "conservation" (274); other popular keywords were "evolution" (277), "population (ecology)" (273), and the rather vague "patterns" (196).
(click image for larger view)
Thursday, November 18, 2010
Biodiversity and ecosystem functioning - only with fungi
Once again scientists have come to an age-old conclusion: fungus is behind all of life’s great mysteries. It's responsible for curing strep throat, delicious veggie burgers, that unique musk emanating from your gym bag, the colour-morphing walls at last night’s party and now, biodiversity and ecosystem functioning.
The world of biodiversity and ecosystem functioning (BEF), like many other high-profile disciplines of science, has often been bogged down by controversy. In such situations, we often spend a disproportionate amount of time focusing on the controversy instead of actually advancing the science itself (sound familiar?)
There have been several posts about BEF on this blog in the last few months, but briefly and oversimplified, here's how it works. Ecosystem functions are things like productivity, nutrient cycling and decomposition. Ecosystems that contain many species produce higher levels of these functions than monocultures do. The controversy here surrounds the cause of this phenomenon. In the 1990s, researchers originally disagreed over whether the relationship they observed was due to complementarity (different species partitioning resources) or selection effects (the higher chance of a really productive species being included in a community with many species). The question was largely settled a few years ago; selection effects do exist, but most of the relationship is driven by complementarity. Nonetheless, many biologists who are only tangentially familiar with this area of research are unaware of the consensus and continue to believe that the issue remains unresolved. Some still dismiss the whole field of BEF because of selection effects. I guess people just love a controversy.
The result of all this is that the ecologists studying these relationships have had to spend an undue amount of time parsing their results into selection and complementarity and discussing the two phenomena. They have even come to refer to these as the “mechanisms” behind BEF. And this is where we start to have a problem. Selection and complementarity are not mechanisms - they are symptoms of mechanisms. They do not tell us what is actually causing the positive effect that biodiversity has on ecosystem functioning, only what the shape of the relationship is. In fact, very few studies have actually looked for true mechanisms that explain the effects that we have repeatedly observed.
But this week I read a new paper in Ecology Letters that actually did find a mechanism, and it wasn’t one that we expected. John Maron and his coauthors at the universities of Montana and British Columbia found that belowground fungi were causing plant productivity to increase with diversity.
In an impressively complete experiment, Maron et al. put together a classic BEF setup of many plots containing varying levels of plant diversity and then measured plant biomass. But this time they added a twist; they applied fungicide to the soil in some of these plots. The result was that in the absence of fungi, the common BEF relationship disappeared. The low diversity plots became much more productive, while productivity at high diversity only increased slightly. The authors explained their results by the fact that fungi can be both species-specific and density-dependent, so as plant diversity increases, the fungi’s negative impact on plant productivity diminishes. And for good measure, they of course also ruled out a significant selection effect in their results.
So what does this all mean? Well for one thing, it means that we now have at least one good mechanistic explanation for that black box that we’ve been calling “complementarity” for years. But perhaps more importantly, it means that the link between biodiversity and ecosystem functioning is now more real than ever. If plant species go extinct, the remaining ones will be more susceptible to fungal pathogens and productivity will decline. So let’s try to not let that happen, k?
Maron, J. L., Marler, M., Klironomos, J. N. and Cleveland, C. C. , Soil fungal pathogens and the relationship between plant diversity and productivity. Ecology Letters, DOI: 10.1111/j.1461-0248.2010.01547.x
Saturday, September 4, 2010
Protecting biodiversity one task at a time: have your say
Maybe the best way forward is not more international governmental summits, but rather focusing on small scale, achievable short term goal. Guillaume Chapron started the Biodiversity 100 campaign, hosted by the Guardian (see story here), which seeks out public and professional input into the 100 immediate and achievable projects or ideas that will help protect biodiversity. The idea is to be able to go to governments and international agencies with this list and get them to make specific pledges to carry out these tasks.
There is till time to participate! If you have an idea of an action to protect biodiversity, fill out the web form. There are already a plethora of great suggestions, from protecting specific habitats to stemming population growth. This list is important because it includes the voices of the international public citizenry and that of scientists. More than that though, there will be a concrete list of tasks (ranging from very local to very global) that citizen groups can use to sustain pressure on governments.
Monday, February 22, 2010
How can evolution inform conservation decisions?
The conservation of biological diversity is a major imperative for biologists. International agreements such as the Convention on Biological Diversity and intergovernmental exercises, such as the Millennium Ecosystem Assessment, call upon scientists to provide evidence on the current state of biological diversity and to evaluate solutions for reducing diversity and ecosystem function loss. Critical to these efforts have been the work of ecologists, conservation biologists and ecological economists. However, seemingly missing from the conversation about the state of biodiversity knowledge has been evolutionary biologists. Are they primarily concerned with describing historical processes and mechanisms of biological change, or do they have substantive knowledge and ideas that should be viewed as a critical component of any scheme to conserve biological diversity?
In a recent paper in Evolution, Hendry and a number of coauthors convincingly make the case that evolutionary biology is a necessary component for conservation. Evolution offer four key insights that should inform conservation and policy decisions. First, they point out that evolutionary biologists are in the business of discovering and documenting biodiversity. They are the primary drivers behind long-term, sustained biological collections, because they need to know what exists in order to better understand evolutionary history. With millions of species awaiting scientific discovery, their efforts are critical to measuring biodiversity. But not only are they discovering new species and enumerating them, they are uncovering their evolutionary relationships, which gives conservationists better information about which species to prioritize. What Vane-Wright famously called 'the agony of choice', with limited resources, we need to prioritize some species over others, and their evolutionary uniqueness ought to be a factor. More than this, evolutionary biologists have developed pragmatic tools for inventorying and sharing data on biodiversity at all levels, from genes to species, which is available for prioritization.
The second key insight is that by understanding the causes of diversification, we can better understand and predict diversity responses to environmental and climatic change. By understanding how key functional traits evolve, we can develop predictions about which species or groups of species can tolerate certain perturbations. Further, research into how and why certain evolutionary groups faced extinction can help us respond to the current extinction crisis. For example, the evolutionary correspondence between coevolved mutualists, such as plants and pollinators, can be used to assess the potential for cascading extinctions. These types of analyses can help identify those groups of related species, or those possessing some trait, which make species more susceptible to extinction.
Thirdly, evolution allows for an understanding of the potential responses to human disturbance. Evolutionary change is a critical part of ecological dynamics, and as environment change can result in reduced fitness, smaller population sizes and extinction, evolution offers an adaptive response to these negative impacts. Knowing when and how populations can evolve is crucial. Evolutionary change is a product of genetic variation, immigration, population size and stochasticity, and if the ability to evolve to environmental change is key for persistence, then these evolutionary processes are also key.
Finally, evolutionary patterns and processes have important implications for ecosystem services and economic and human well-being. Both genetic and evolutionary diversity of plant communities has been shown to affect arthropod diversity, primary productivity (including work by me) and nutrient dynamics. Thus understanding how changes in diversity affect ecosystem processes should consider evolutionary processes. Further, exotic species are often cited as one of the major threats to biodiversity, and evolutionary change in exotics has been shown to increase exotic impacts on native species.
All together, these key reasons why evolution matters for conservation, mean that developing sound management plans requires considering evolution patterns and processes. We can use evolution to our benefit only if we understand how evolution shapes current dynamics. The challenge to evolutionary biologists is the same as it was for ecologists perhaps 15 to 20 years ago, to present their understanding and conservation ideas to a broader audience and to engage policy makers. To this end, the authors highlight some recent advances in incorporating evolutionary views into existing biodiversity and conservation programmes –most notably into DIVERSITAS.
Just like ecological processes and dynamics cannot be fully understood without appreciating evolution ancestry or dynamics, developing an extensive, expansive conservation strategies must take into account evolution. I hope that this paper signals a new era of a synthesis between ecology and evolution, which produces precise, viable conservation strategies.
Hendry, A., Lohmann, L., Conti, E., Cracraft, J., Crandall, K., Faith, D., Häuser, C., Joly, C., Kogure, K., Larigauderie, A., Magallón, S., Moritz, C., Tillier, S., Zardoya, R., Prieur-Richard, A., Walther, B., Yahara, T., & Donoghue, M. (2010). EVOLUTIONARY BIOLOGY IN BIODIVERSITY SCIENCE, CONSERVATION, AND POLICY: A CALL TO ACTION Evolution DOI: 10.1111/j.1558-5646.2010.00947.x
Thursday, January 7, 2010
Double or nothing
Monday, November 2, 2009
Eco-label Promotes Biodiversity on Farms
At first glance, potato farms might seem like an unlikely candidate for conservation efforts.
But Wisconsin researchers are demonstrating that biodiversity can be restored even in the midst of large-scale farming.
Paul Zedler, professor of Environmental Studies at the University of Wisconsin (UW)-Madison, and his colleagues are working with potato farmers to restore pre-settlement habitats on growers’ lands.
In central Wisconsin, 42,600 acres are devoted to potatoes. Since the landscape is dominated by agriculture, some proportion of farmland must be set aside for conservation to preserve biodiversity in this part of the state.
Restoration is a requirement of the Wisconsin Healthy Grown potato program, a partnership between UW–Madison, the Wisconsin Potato and Vegetable Growers’ Association, and NGOs such as the International Crane Foundation, Defenders of Wildlife, and the World Wildlife Fund.
The groundwork for the Healthy Grown program was laid out in the 1980s, when a group of potato growers voluntarily discontinued use of the high-risk pesticide aldicarb. The farmers turned to UW-Madison researchers for pest-management advice. This grassroots movement eventually drew attention from conservation agencies.
To be certified under the Healthy Grown eco-label, potatoes must be grown under a set of standards that restrict pesticide and fertilizer use. The program was able to draw from an extensive body of UW-Madison research to guide the formulation of these in-field standards. But farmers and environmentalists were interested in doing more.
Since the program's conception, growers had expressed interest in managing their farms as whole ecosystems rather than just focusing on crop production on a field by field basis. At the same time, the NGOs saw the program as an opportunity to bring farmland into regional-scale conservation plans.
Satisfying this interest in developing a conservation standard for the eco-label was challenging for researchers because fewer precedents existed. Even the largest and most well-known eco-label, USDA Organic, does not include a conservation requirement in its certification standards.
Zedler and his colleagues looked to the Nature Conservancy, which had established a system for making strategic conservation decisions and measuring conservation success at sites where the objective is to improve biodiversity on whatever land can be spared from intensive human use.
Potato farms in central Wisconsin are unusual in their tendency to contain significant patches of marginal land without crops because these patches cannot be irrigated – a necessary factor in growing potatoes. The result is a complex mosaic of land in which remnant patches of disturbed natural habitat are isolated within an agricultural matrix. Zedler and his colleagues focused their research efforts on these patches of non-crop land.
Their research suggests that prescribed burns and control of invasive plant species can help restore disturbed non-crop land to the habitats that characterized central Wisconsin before European settlement: prairie, oak-pine savannah, and sedge meadow.
Thus far, the Healthy Grown program has restored more than 400 acres of privately owned farmland. According to Zedler and his colleagues, farmers’ strong ties to their land motivate their commitment to the conservation standard of the Healthy Grown eco-label.
Zedler, P. H., T. Anchor, D. Knuteson, C. Gratton, and J. Barzen. 2009. Using an ecolabel to promote on-farm conservation: the Wisconsin Healthy Grown experience. International Journal of Agricultural Sustainability 7(1): 61-74. DOI:10.3763/ijas.2009.0394
(Image courtesy of FotoosVanRobin at flickr under a Creative Commons license)