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The Millennium Ecosystem Assessment (World Resources Institute Millennium Ecosystem Assessment 2005) provided a framework that acknowledges biodiversity as one key factor for ensuring the continuous supply of ecosystem services, facilitating ecosystem stability and consequently as a critical basis for sustainable development. The close connection between biodiversity and basic ecosystem services (e.g., primary production, soil formation, and nutrient recycling) as well as final ecosystem services (e.g., provision of water, food, and feed) is central to the 2020 targets set in the Convention on Biological Diversity, providing one of the foundations for the United Nations Intergovernmental Platform on Biodiversity and Ecosystem Services (http://www.ipbes.net). Strategies are currently being discussed for integrating the concept of ecosystem services into existing chemical regulations, e.g., the Clean Water Act (Ruhl 2011).

Impacts on biodiversity are particularly critical as they have tremendous direct or indirect effects on most, if not all, ecosystem services—but are almost impossible to mitigate as soon as they occur on a larger scale. Biodiversity also provides an “insurance policy” that minimizes the risk of drastic changes in ecosystems as a response to stressors: the larger the number of functionally related species in an ecosystem, the greater the chance that some of them will be resilient to a particular stressor. However, it is often unclear whether the relationship between a particular ecosystem service and biodiversity is linear or nonlinear, and whether abrupt thresholds exist. It is also largely unknown how associated societal costs respond to decreases in biodiversity.

Society has benefited tremendously from chemical use. However, chemical pollution has also been put forward as 1 of the 5 main pressures that negatively affect global biodiversity, the other 4 pressures being habitat loss, the unsustainable use and overexploitation of resources, climate change, and invasive alien species (Secretariat of the Convention on Biological Diversity 2010). However, beyond this general notion, our current knowledge on detrimental effects of chemical exposure on biodiversity is largely restricted to excessive nutrient loads, acid rain, and other comparatively simple pollution scenarios.

To safeguard against undesirable side effects of chemical pollution, a network of interlinking (and, unfortunately, sometimes conflicting, see e.g., Moermond et al. 2011) legal provisions, rules, and guidelines has been put into place on subnational, national, and transnational levels. Many of these guidelines and provisions were developed during a period when chemical effects were often local, driven by point sources that emitted a limited number of compounds that had easily detectable, often acutely toxic effects on exposed organisms. Since then, the greening of the chemical industry processes, enhanced recovery of resources, and extensive intensification of wastewater treatment have substantially decreased the input of many point sources, at least in most industrialized nations.

However, even a cursory glance at the Web site of the American Chemical Society (www.cas.org) reveals that new chemicals are discovered and described at an unprecedented speed: during a 24-h period in July 2012, more than 700 new chemicals were entered into the Chemical Abstracts Service database, which corresponds to a discovery rate of more than 30 new chemicals per hour. In 2007, McKinney and Schoch estimated an average discovery rate of even 70 new chemicals per hour (McKinney and Schoch 2007). Of course, only a small percentage of these newly described chemicals will ever be produced on a commercial scale, but such figures provide a glimpse of the enormous dynamics underlying chemical discovery and use.

Chemical use and exposure patterns have drastically changed over the last decades. Society is now challenged to assess and manage the consequences of continuous, low-dose contamination with highly complex multicomponent mixtures of extremely heterogeneous chemicals. These often originate from diffuse sources, potentially having subtle long-term effects on wildlife, ecosystem structure, stability, and function, as well as on human health. Unfortunately, the sheer complexity of assessing this situation sometimes tempts extreme reactions: alarmism and avoidance. Both reactions are obviously detrimental for finding scientifically robust solutions and chemical management options. The public policy paralysis that currently cripples the public discourse in many countries also adds significantly to the problem.

It is a generally accepted paradigm that protecting ecosystem structure also protects its functions and services. It follows, therefore, that strategies for evaluating chemical risks should consider effects on ecosystem structure and biodiversity. However, environmental hazard assessment regimes implemented in the context of registration and authorization of chemical products often assess effects only at the individual or population levels. This is also usually limited to the determination and quantification of impacts on growth or reproduction in simple assays with the usual suspects, i.e., standard aquatic test species such as unicellular green algae and daphnids, or earthworms as representatives for the terrestrial environment. A notable exception is pesticides, for which impacts on biodiversity are frequently assessed.

Biodiversity assessments are also too often driven solely by endangered charismatic species. With respect to potential impacts on environmental microbes, chemical risk assessment and management measures are usually limited to safeguarding selected beneficial microbial functions such as the degradation of organic matter or nitrification. We are only at the beginning of understanding the broader role of microbial diversity. However, evidence is mounting that microbial diversity is a vital component that ensures long-term ecosystem functions, ecosystem resilience to stressors in general, and the provision of ecosystem services.

For example, microbial biodiversity has been linked to increased nutrient cycling and availability, as well as increased degradation of organic matter (see overview in Cardinale et al. 2012). The importance of microbial diversity for ecosystem stability can be illustrated by the decreased risk of fungal infections resulting from competition and interference among microbes (Chapin et al. 2000). We are also starting to comprehend that microbial biodiversity in the environment might have a direct impact on human health. For example, Hanski et al. (2012) demonstrated a clear correlation between the diversity of skin-living Gammaproteobacteria and allergic disposition.

There is an intricate, context-driven, and largely unidentified interconnection between microbial biodiversity and ecosystem status, ecosystem services, and human health. What seems clear, however, is that a loss in microbial biodiversity most often has severe negative consequences. The systematic development, validation, and application of bioassays that determine the impacts of chemicals on microbial biodiversity is hence required—to provide fundamental scientific knowledge, but also to then facilitate the development of appropriate regulatory strategies. Modern microbiological approaches that allow the genomic (16/18S-sequencing, next-generation sequencing), proteomic, and metabolomic characterizations of natural microbial communities might be of tremendous value in this context.

We need to go beyond a mere phonebook approach (recording who is there) to providing the ecosystem's yellow-pages (recording who is there, and who is doing what). For example, the combination of functional and biodiversity analysis of the gut microflora from honeybees (Engel et al. 2012) provides insights into the ecological, physiological, and microbiological networks, whose disturbance (caused by a combination of environmental factors, exposure to pesticides and pathogens), might be ultimately responsible for the current surge of bee hive collapses.

Chemical production, use, and disposal play a crucial role in a world that is transformed by human activities with an ever-increasing speed. Impacts on biological diversity must be accounted for when tallying the costs and benefits of chemical use in society. We need to shed more light on the relationship between biodiversity, ecosystem status, and exposure to naturally occurring and man-made chemicals. More work is needed to deliver a scientifically sound, impartial basis for improved chemical risk assessment and management decisions that pave the way toward sustainable chemical use. As Naeem et al. (2012) so aptly stated in Science, we need to go “beyond merely invoking the precautionary principle of conserving biodiversity to a predictive science.”

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The views expressed in this article are those of the authors and do not necessarily represent the views or policies of the US Environmental Protection Agency.

REFERENCES

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  3. REFERENCES
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