A scientist working for an environmental advocacy group in Indonesia fights against the transfer of a portion of state owned native forest to a palm-oil plantation. The case raises ethical issues including how to establish the value of natural lands, environmental justice, and communicating science.
This biodiversity case is part of a larger collection of Life and Environmental Science ethics education resource sets on ethics of emerging biotechnologies, big data in the life sciences, human enhancement, and conservation and biodiversity. Doctoral students from Arizona State University’s Center for Biology and Society developed the resources under the direction of Karin Eand conservation and biodiversity. Doctoral students from Arizona State University’s Center for Biology and Society developed the resources under the direction of Karin Ellison and Joseph Herkert between 2014 and 2019.
The archipelago country of Indonesia contains one of the world’s twenty-five “biodiversity hotspots” (Myers et al. 2000). Such “hotspots” are locations on the planet that are home to exceptional concentrations of variety of life, particularly in terms of endemic species. Indonesia is also home to a large and growing population of over 250 million people living at a density of 142 people per square kilometer (World Bank 2016). (For comparison, almost 320 million people live in the United States at a density of 35 people per square kilometer.) To meet the economic and social demands of a dense, large, and growing population, some areas of the Indonesian islands have been developed for urban, industrial, and agricultural uses. Unfortunately, such development is sometimes in close proximity to and threatens destruction of the ecosystems that constitute Indonesia’s biodiversity hotspot.
Kiera—a recent PhD graduate of a large university in the United States—has returned to the Indonesian island, Sumatra, where she was born and raised to work for a local chapter of an NGO, Friends of the Earth International. In Sumatra, Friends of the Earth and Kiera are fighting against the transfer of a portion of state owned native forest to a palm-oil plantation. Past efforts to halt plantation expansion relied on emphasizing the spiritual and intrinsic (existence) value of the biodiversity in the forest. Plantation owners, employees, and some local villagers argued that the plantation harbors economic benefits that outweigh the non-monetary value of the intact ecosystem.
Although agriculture will bring short-term economic benefits to the community, the long-term costs of lost biodiversity may be severe. Recently, Kiera learned that destruction of biodiversity could have human health implications. In particular, recent studies have shown that decreasing levels of biodiversity may lead to an increase in outbreaks of vector-borne and parasitic diseases, such as malaria, dengue, zika, and schistosomiasis (all occurring in Indonesia) (Bonds et al. 2012; Morand et al. 2014; Keesing and Ostfield 2015). Outbreaks may necessitate a costly healthcare response. In addition, there are studies linking disease outbreaks to poverty (Garchitorena et al. 2015; Bonds et al. 2010; Bloom and Canning 2000).
Furthermore, the endangerment of local lives due to nearby environmental degradation could be considered a violation of environmental justice (the fair treatment of all people with respect to environmental laws, policies, and regulations).
Due to the potential public health costs and environmental justice violation there will be a public vote regarding expansion of the plantation (a democratic decision process in an only recently democratic nation). In advance of the vote, Kiera’s organization has charged her with putting together a public education forum. However, some of the evidence for disease outbreaks in response to declining biodiversity is conflicting. Kiera has decided to focus on the academic literature and media that claim biodiversity destruction is likely to lead to disease outbreaks. This way, she believes she is more likely to persuade locals who will feel they are endangered by palm plantation expansion. Perhaps she will initiate a local environmental justice movement.
Allan, B. F., R. B. Langerhans, W. A. Ryberg, W.J. Landesman, N. W. Griffin, R. S. Katz, ... and L. Clark. 2009. Ecological Correlates of Risk and Incidence of West Nile Virus in the United States. Oecologia 155: 699-708.
Barclay, E. 2010. “Declining Biodiversity Speeds Spreading of Disease.” NPR Environment, December 2. http://www.npr.org/2010/12/02/131758921/declining-biodiversity-speeds-spreading-of-disease
Barclay, E. 2012. “As Biodiversity Declines, Tropical Diseases Thrive.” NPR Public Health, December 29. http://www.npr.org/sections/health-shots/2012/12/29/168210441/as-biodiversity-declines-tropical-diseases-thrive
Bloom, D. E., and D. Canning. 2000. “The Health and Wealth of Nations.” Science 287: 1207-1209.
Bonds, M. H., D. C. Keenan, P. Rohani, and J. D. Sachs. 2010. Poverty Trap Formed by the Ecology of Infectious Diseases. Proceedings of the Royal Society Biological Sciences 277: 1185-1192.
Bonds, M. H., A. P. Dobson, and D. C. Keenan. 2012. “Disease Ecology, Biodiversity, and the Latitudinal Gradients in Income.” PLoS Biology 10: e1001456.
Civitello, D. J., J. Cohen, H. Fatima, N. T. Halstead, J. Liriano, T. A. McMahon, C. N. Ortega, E. L. Sauer, T. Sehgal, S. Young, and J. R. Rohr. 2015. “Biodiversity Inhibits Parasites: Broad Evidence for the Dilution Effect.” PNAS 112: 8667-8671.
Douglas, M., and A. Wildavsky. 1982. Risk and Culture. Berkeley: University of California Press.
Ezenwa, V. O., M. S. Godsey, R. J. King, and S. C. Guptill. 2006. “Avian Diversity and West Nile Virus: Testing Associations Between Biodiversity and Infectious Disease Risk.” Proceedings of the Royal Society London B 273: 109-117.
Garchitorena, A., C. N. Ngonghala, J. Guegan, G. Texier, M. Bellanger, M. Bonds, and B. Roche. 2015. “Economic Inequality Caused by Feedbacks Between Poverty and the Dynamics of a Rare Tropical Disease: The Case of Buruli Ulcer in Sub-Saharan Africa.” Proceedings of the Royal Society Biological Sciences 282: 20151426; DOI: 10.1098/rspb.2015.1426.
International Monetary Fund (IMF). 2009. World Economic Outlook, October 2009: Sustaining the Recovery. Washington D.C.: International Monetary Fund.
Keesing, F. and R. S. Ostfeld. 2015. “Is Biodiversity Good for Your Health?” Nature 349: 235-236.
Keesing, F., L. K. Belden, P. Daszak, A. Dobson, C. D. Harvell, R. D. Holt, ... and S. S. Myers. 2010. “Impacts of Biodiversity on the Emergence and Transmission of Infectious Diseases.” Nature 468: 647-652.
Keesing, F., R. D. Holt, and R. S. Ostfeld. 2006. “Effects of Species Diversity on Disease Risk. Ecology Letters 9: 485-498.
Lopez A. D., C. D. Mather, M. Ezzati, D. T. Jamison, and C. J. L. Murray. 2006. Global Burden of Disease and Risk Factors. Washington D.C.: World Bank.
Mace, G. M., H. Masundire, and J. E. M. Baillie. 2005. In Ecosystems and Human Well-Being: Current State and Trends: Findings of the Condition and Trends Working Group, Vol. 1, Ch. 4. Millennium Ecosystem Assessment Series. Washington D.C.: Island Press.
McCauley, D. J. 2006. “Selling Out On Nature.” Nature 443: 27-28.
Millennium Ecosystem Assessment. 2005. Ecosystems and Human Well-Being: Synthesis. Washington, D.C.: Island Press.
Morand, S., S. Jittapalapong, Y. Suputtamongkol, M. T. Abdullah, and T. B. Huan. 2014. “Infectious Disease and Their Outbreaks in Asia-Pacific: Bio-diversity and Its Regulation Loss Matter.” PLoS ONE 9: e90032.
Myers, N., R. A. Mittermeier, C. G. Mittermeier, G. A. B. da Fonseca, and J. Kent. 2000. “Biodiversity Hotspots for Conservation Priorities.” Nature 403: 853-858.
Pielke, Jr., R. A. 2007. The Honest Broker: Making Sense of Science in Policy and Politics. Cambridge: Cambridge University Press.
Reyers, B., S. Polasky, H. Tallis, H. A. Mooney, and A. Larigauderie. 2012. “Finding Common Ground for Biodiversity and Ecosystem Services.” Bioscience 62: 503-507.
Runte, A. 2010. National Parks: The American Experience. Lanham, MD: Taylor Trade Publishing.
Salkeld, D. J., K. A. Padgett, and J. H. Jones. 2013. “A Meta-Analysis Suggesting that the Relationship Between Biodiversity and Risk of Zoonotic Pathogen Transmission is Idiosyncratic. Ecology Letters 16: 679–686.
Sandifer, P. A., A. E. Sutton-Grier, and B. P. Ward. 2015. “Exploring Connections Among Nature, Biodiversity, Ecosystem Services, and Human Health and Well-Being: Opportunities to Enhance Health and Biodiversity Conservation. Ecosystem Services 12: 1-15
Swaddle, J. and P. Calos. 2008. Increased Avian Diversity is Associated with Lower Incidence of Human West Nile Infection: Observation of the Dilution Effect. PLoS ONE 3: e2488.
UNCTAD. 2008. The Least Developed Countries Report 2002. New York and Geneva: UNCTAD.
United Nations. 2016. “Sustainable Development Goals.” Accessed July 15.
US Environmental Protection Agency (EPA). 2016. “Environmental Justice.” Accessed July 11. https://www.epa.gov/environmentaljustice
Wood, C. L., et al., 2014. “Does Biodiversity Protect Humans Against Infectious Disease?” Ecology 95: 817-832.
World Bank. 2016. “Population Density.” Accessed July 8. http://data.worldbank.org/indicator/EN.POP.DNST
World Health Organization. 2016. “Climate Change and Human Health: Biodiversity.” Accessed July 11. http://www.who.int/globalchange/ecosystems/biodiversity/en/
World Health Organization:
Convention on Biological Diversity:
Posted 1 month and 2 weeks ago
Author: Elizabeth Lyons, NSF Office of International Science and Engineering
This material is based upon work done while serving at the National Science Foundation. Any opinion, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation.
This case study addresses several important ethical issues around the topic of biodiversity and human health. I also see it as a useful starting point for guiding OEC users to a wider range of issues around the ethics of international biodiversity research and environmental action.
By having the study’s protagonist be native to and working in Indonesia, the case study misses the chance to ask what ethical issues OEC users based at American institutions might consider when they work in foreign countries in areas such as biodiversity research or conservation. I propose a few issues, but this is not an exhaustive set.
First, for anyone doing biodiversity research, a fundamental tenet of international law (i.e., the Convention on Biological Diversity or CBD) is that nations have sovereign control of their biological resources and that scientific needs do not override a country’s rules. This means that all researchers must secure the required research permits, collections permits and/or material transfer agreements for each area in which they work; the requirements and processes can vary within and between countries. In the past, non-compliance with such requirements has had serious negative consequences for some researchers, students, projects, U.S. universities and even international relationships between the United States and other countries. Alas, right now the ethical path, i.e., following those rules, can be especially cumbersome and time-consuming because many countries are working to develop or revise their biodiversity-related rules to comply with the 2014 addition to the CBD treaty, known as the Nagoya Protocol (NP) on Access and Benefit Sharing of Genetic Resources. The NP website and the CBD’s Access and Benefit-Sharing Clearing-House have a vast array of country-specific information that could assist many OEC users, especially researchers, follow the right steps; a guest blog that I wrote on this shifting landscape also provides some tips for researchers.
A second issue in foreign countries is that the ethical landscape around biodiversity, i.e., the sets of values held by different groups, can be vastly different than those familiar to American scientists. When I taught a course on tropical deforestation with an economist several decades ago, I discovered a rich literature on the various value constructs underlying human-nature relationships, including the Judeo-Christian stewardship perspective that underlies many conservation efforts, as well as beliefs shaped by other religions, and by secular, utilitarian/economical, interconnectivity, and deep ecology/intrinsic views, for example. Understanding how these views play out is difficult in a country like Indonesia that is both biologically and culturally rich (e.g., with more than 700 languages, and large Muslim, Christian and Hindu populations); one cannot assume that various foreign communities will embrace the mainstream scientific mindset that U.S. researchers might carry. (Note that this is not just an international issue — Native American peoples can also have different values that guide human-nature interactions within their sovereign nations). More in-depth consideration of these topics can be found by OEC readers in journals such as Environmental Ethics; Culture Matters, a report by a National Academies group, also touches on the importance of many facets of culture in arranging fair, equitable and successful international research partnerships, including in environmental fields.
The case study refers to a potential ethical conflict posed by choosing between a forest’s spiritual/intrinsic value and the economic value it might yield for humans via the ecosystem services it provides. OEC readers can examine this potential conflict more deeply by tapping into the worldwide IPBES community that is forging consensus on the valuation and conservation of ecosystem services. IPBES, the Intergovernmental Platform on Biodiversity and Ecosystem Services, is an international agreement established in 2012 and signed by 126 countries, including the United States. (I was honored to be part of the U.S. delegation to the First IPBES Plenary in 2013). OEC readers will find that a recent paper by the IPBES Expert Group on Ecosystem Values, with 48 authors from 31 countries, brings a wide range of international, cultural and scientific perspectives to the valuation of ecosystem services and most importantly, expands the discussion from an intrinsic vs. human economic valuation to a pluralistic approach that incorporates diverse values: “Valuing nature’s contributions to people: the IPBES approach".
And finally, the case study addresses how scientists can better explain environmental uncertainty. OEC readers might find it valuable to peruse relevant publications by the National Academies of Science (e.g., Environmental Decisions in the Face of Uncertainty, 2013), or a report from the U.S. Global Change Research Program, “Best Practice Approaches for Characterizing, Communicating and Incorporating Scientific Uncertainty in Climate Decision Making,”, which has very good sections on how to understand environmental uncertainty and explain it to the public.
Posted 6 months, 3 weeks and 2 days ago
In this case, Kiera confronts a variety of roadblocks and ethical dilemmas. First she must contemplate different ways the community could value the forest and its biodiversity (“Ecosystem Services”). Then, she must explore the literature related to “Biodiversity and Disease” to ensure a complete understanding of the points of consensus and of disagreement in the research community. Of course, this is an issue for more than just scientists. Kiera should be fully aware of social and political implications of the research as well (“Environmental Justice and Disease Management”). Finally, Kiera will need to consider how to best communicate the research, including uncertainties, to the public, and this requires a decision regarding what the role of science should be in making a public policy decision about the forest (“Communicating Science and the Role of Science in Public Policy”).
One major issue that Kiera will contend with is to decide how the forest is valuable and which of those values she will utilize in an argument to protect the forest. There are many ways to value a forest; these values may be tangible or intangible, economic or spiritual, human-centered (anthropocentric) or nature-centered (ecocentric). And one could argue that these values are or are not mutually exclusive.
In 2001, called into action by the United Nations (UN) Secretary General, the Millennium Ecosystem Assessment (MEA) initiated a major evaluation of human impacts on the environment. The MEA panel released their synthesis report, “Ecosystems and Human Well-Being,” in 2005, and in it they popularized the term “ecosystem services” to name the benefits human gain from healthy ecosystems (Millennium Ecosystem Assessment 2005). In 2015, the UN released the Sustainable Development Goals, a set of targets and topics they hope to address by 2030. Reiterated in the goals are commitments to reduce poverty and protect life both on land and in water (United Nations 2016).
The appeal by the UN and others, including the Nature Conservancy, to value biodiversity in economic or instrumental (how biodiversity can be useful to humans) terms, has encountered pushback from some in the science and environmental communities. In a heavily circulated essay published in Nature in 2006, Stanford biologist Douglas McCauley argued that instrumental valuation of nature is flawed because it cannot guarantee protection of biodiversity in perpetuity. Markets fluctuate, and so too will the market value for a given ecosystem service. Additionally, technological advancements by humans may eventually replace services provided by an ecosystem, and thus make protection of that ecosystem unnecessary in instrumental terms. Finally, some ecosystems simply do not provide any obvious or market-valued services to humans (McCauley 2006).
When dealing with governments and businesses, however, it may be more effective to negotiate in economic terms. For example, when the earliest U.S. National Parks were proposed to Congress, it was the appeal to tourism dollars and the railroad industry that convinced doubtful Congress members to back the parks (Runte 2010). Still today, the National Park Service releases extensive reports detailing the financial benefits that park units bring to local communities and the national economy.
Perhaps, as Belinda Reyers (scientist for the South African Council for Scientific and Industrial Research) and her colleagues argue, the best path forward is to use a combination of instrumental and intrinsic value arguments to support biodiversity conservation: “If this debate leads to polarization of the conservation community, it may prevent the emergence of common understanding of how best to push forward with conservation, which in our experience, is what all sides of the current debate desire” (Reyers et al. 2012, 506).
Assuming that Kiera does decide to bring attention to the ecosystem services that the biodiversity in the Indonesian forest provides, human health could be a significant focal point for her argument. According to the World Health Organization (WHO), human health “ultimately depends upon ecosystem products and services (such as availability of fresh water, food and fuel sources)...” Directly related to biodiversity, healthy ecosystems can also harbor a variety of species that may have pharmacological value- an ecosystem service that could directly benefit progress in medical science. (WHO 2016).
Biodiversity and Disease
In the last decade, much research has been conducted to better understand another potential ecosystem service provided by biodiversity: disease control. Reductions and alterations in biodiversity have cascading effects on biogeochemical interactions throughout an ecosystem to which infectious diseases are sensitive. Specifically, researchers have found that intact biodiversity acts to regulate and control vector-borne and parasitic diseases. However, the research community is not in unanimous agreement; some researchers claim that there is no connection between biodiversity and disease control. Kiera will need to wade carefully through the competing claims and carefully present uncertainty in the research to the public and to government officials.
In 2006, Bard College biologist Felicia Keesing and colleagues first reported an “inverse relationship between [bio]diversity and disease risk,” which they termed the “dilution effect” (Keesing et al. 2006). The dilution effect describes the process by which greater levels of biodiversity will decrease (dilute) the chances that a pathogen will meet its host. When a system contains more species, there are more opportunities to interrupt the life cycle of a disease, and there exists a smaller concentration of vectors for the disease (Bonds in Barclay 2012). Declines in biodiversity tend to eliminate species that prey on vectors for disease. And often, the animals that survive biodiversity declines are the “weedy species,” those that are likely to be good disease hosts (Keesing et al. 2010; Barclay 2010).
In a 2012 study, Harvard professor Matthew Bonds and colleagues found that countries with high levels of biodiversity (such as biodiversity hotspot, Indonesia), will see a 30% increase in disease burden should 15% of biodiversity be lost. This finding could be alarming, considering that increasing human development has led to unprecedented biodiversity loss, with current extinction rates at least 100 to 1000 times background rates and future rates (in the next 50 years) predicted to be 10 to 100 times present rates of extinction (Mace et al. 2005).
Claims concerning the inverse relationship between biodiversity and disease outbreaks are disputed. A meta-analysis found weak support for the dilution effect (Salkeld et al. 2013), and another concluded that the relationship is far too complex to come to any conclusion (Wood et al. 2014). Most recently, a review published by NOAA Senior Science Advisor, Paul A. Sandifer, and colleagues (2015) argues that although there is “strong evidence linking biodiversity with production of ecosystem services and between nature exposure and human health,” most “studies were limited in rigor and often only correlative” (emphasis added). But their conclusion is caveated: “we believe the best current answer to the question of whether increased biodiversity reduces risk from infectious diseases is ‘probably not, but it depends.’ This question requires further research about the mechanisms and effects of biodiversity on disease transmission…” (Sandifer et al. 2015). Even studies that assert to have evidence for the inverse relationship between biodiversity and disease outbreaks admit that more research is needed to determine a mechanism of causation and to formulate a general theory on the effect of biodiversity on disease control (Bonds et al. 2012; Morand et al 2014; Citivello et al. 2015).
In general, however, the Keesing et al. (2006) team’s initial findings have been supported in the literature with studies showing patterns resembling the dilution effect for malaria in particular, (Allan et al. 2009; Ezenwa et al. 2006; Swaddle and Calos 2008), in addition to meta-analyses detecting similar patterns across vector-borne and parasitic diseases more generally (Bonds et al. 2012; Morand et al. 2014; Civitello et al. 2015; Keesing and Ostfield 2015).
Environmental Justice and Disease Management
The Bonds et al. (2012) study also demonstrates the negative economic impacts of disease burdens. This is a not a new idea; previous studies have linked disease outbreaks to poverty (Garchitorena et al. 2015; Bonds et al. 2010; Bloom and Canning 2000). Bonds et al. claim that such economic effects could explain the differences in income among tropical and temperate regions. And indeed, poverty and disease have similar, distinctive geographic distributions. The tropics hold 93% of the global burden of vector-borne and parasitic diseases and are home to 41 of the 48 “least developed countries” and only two of 34 “advanced economies” (Lopez et al. 2006; UNCTAD 2008; IMF 2009).
Though more research is needed to see if there is causation underlying this correlation, Bonds et al. (2012) argue that the manner in which income increases with latitude “is highly suggestive of underlying biophysical drivers” particularly because vector-borne and parasitic diseases spend much of their life cycle outside the human host, and are thus dependent on environmental conditions (including levels of biodiversity).
The links among biodiversity, vector-borne and parasitic diseases, and poverty have environmental justice implications. According to the US Environmental Protection Agency, “Environmental justice is achieved when everyone, regardless of race, culture, or income, enjoys the same degree of protection from environmental and health hazards and equal access to the decision-making process to have a healthy environment in which to live, learn, and work” (EPA 2016; emphasis added). If lesser income communities and countries are more often subject to human activities that destroy biodiversity and instigate disease outbreaks, then environmental justice is not fulfilled. Perhaps one policy outcome of this body of research is that local communities should be informed of the possible disease risk that accompanies biodiversity destruction and be consulted before nearby human development that threatens endemic species and ecosystems occurs.
Understanding the relationship between biodiversity and disease could also change policies for management of tropical diseases. Tropical diseases are typically managed as medical and public health issues, but perhaps public health officials and tropical disease specialists should also note the role of biodiversity in disease outbreaks, especially for diseases that spend parts of their life-cycle outside of humans (Barclay 2012). The potential role of biodiversity conservation in tropical disease management has not escaped the attention of the WHO: “‘If we see biodiversity loss increasing infectious disease transmission as a general rule, that’s an argument for conservation […],’ says Diarmid Campbell-Lendrum, a senior expert on health and environment at WHO” (Quoted in Barclay 2010).
Communicating Science and the Role of Science in Public Policy
Kiera now has the tricky task of communicating the science, as well as the social and political implications, to the community of stakeholders. She will encounter the difficulty of conveying scientific uncertainty to a public audience, and she and the community will need to decide how scientific findings should be used in the policy sphere.
If disease control and protection of human health truly are quantifiable ecosystem services, they should be considered among the list of other ecosystem services provided when weighing decisions regarding human development and biodiversity conservation (Bonds et al. 2012; Keesing and Ostfield 2015). The trouble is that whether or not policy makers believe and act on this claim depends on which experts and literature are consulted and how that information is interpreted. In the US, disagreement among experts would likely lead to political gridlock with both sides of an argument finding evidence to substantiate their positions. In other countries and cultures, you may find a different outcome. For example, many countries in the European Union interpret contested scientific findings in light of the precautionary principle, under which the existence of substantial literature showing a connection between biodiversity loss and health risk would be enough to drive policy decisions to avoid potential risk.
Whether Indonesia operates more like the US or the EU, Kiera has an obligation to present both sides of the debate to the public, to the plantation employees, and to the government. There are a few ways she can describe the uncertainty found in the scientific literature. First of all, natural systems such as the Indonesian forest are inherently variable. This variability encompasses the effect that biodiversity has on disease outbreaks. It is possible that a scientific consensus regarding the effects of biodiversity declines on disease may never be reached because of the considerable randomness that exists in the natural world. In addition to the endemic uncertainty of the study subject, the perspectives of the scientists themselves are varied and affect both the questions and hypotheses they pose, as well as the methods they use to address them (Pielke 2007).
If disagreement over this relationship was a purely scientific issue, why hasn’t over a decade of continued, intensive scientific research settled the debate? In their classic essay, Risk and Culture, Dame Mary Douglas and Aaron Wildavsky, an anthropologist and a political scientist respectively, argue that the reasoning behind a continued debate like this is due to the fact that risks (including the risk of disease outbreaks) have both objective and subjective facets (1982). Though science can advance our knowledge, including awareness of what we don’t know, it cannot reduce uncertainty, particularly the political strain. Douglas and Wildavsky quote Philip Handler, President of the National Academy of Science from 1969-1981, “The estimation of risk is a scientific question… The acceptability of a given level of risk, however, is a political question, to be determined in the political arena” (Douglas and Wildavsky 1982, 65).
Although Handler’s point is not entirely sound (estimation of risk is also subject to politicization, particularly in terms of the assumptions that different risk estimation tools make), the general premise stands. The role of science is to understand how different choices can lead to different outcomes. The role of politics then, is to choose which outcomes and thus which choices are acceptable (in Kiera’s case, by way of public forum and vote) (Pielke 2007).