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Ecotoxicology in the Anthropocene: Are We Listening to Nature’s Scream?
Environ. Sci. Technol. Downloaded from pubs.acs.org by 185.252.218.183 on 09/09/18. For personal use only.
Farhan R. Khan* Department of Science and Environment, Roskilde University, Universitetsvej 1, PO Box 260, 4000 Roskilde, Denmark and what stratographic layer marks the beginning of the Anthropocene from the Holocene,4 the irrefutable evidence of human impacts, regardless of the start date, is overwhelming. It is not just climate change, but also ocean acidification, land system use and stratospheric ozone depletion. In total nine planetary boundaries have been identified that have the capability to drive the Earth system into a new state and this includes anthropogenic chemical inputs.5 Yet in discussions of the Anthropocene, ecotoxicology is rarely mentioned and this needs to be addressed. Ecotoxicology is a field born entirely of the Anthropocene and should be at the forefront of the conversation to mitigate and reverse human-driven impacts. With eight million chemicals commercially available and only a minute fraction (>100 000) subject to assessment,6 the scale of the problem facing ecotoxicologists is daunting. The task becomes exponentially more difficult when considering the interactions
“I was walking down the road with two friends when the sun set; suddenly, the sky turned as red as blood. I stopped and leaned against the fence, feeling unspeakably tired. Tongues of fire and blood stretched over the bluish black fjord. My friends went on walking, while I lagged behind, shivering with fear. Then I heard the enormous infinite scream of nature.” Edvard Munch, 1895. Written by Norwegian artist Edvard Munch as a later accompaniment to his famous 1893 painting “The Scream” (Figure 1), this poem is a description of the apparent internal anguish felt by the author during what was initially a relaxing evening stroll with friends.1 However, the “scream of nature” is perhaps becoming a fitting epiphet for the environment in the Anthropocene. The challenge for ecotoxicologists is now to hear the cry and determine whether the current practices of our discipline are forward-thinking enough to answer the call.
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ECOTOXICOLOGY AND THE ANTHROPOCENE It seems that not a day goes by without a newsworthy article describing the detrimental impact that our species has on our planet. A recent example being the destabilization of the Earth’s climate to such an extent that global temperatures may rise as to create a “Hothouse Earth”.2 Such articles build a convincing case for the Anthropocene, the term popularized by Crutzen (2002),3 to describe the current geological time frame where humankind has established itself as the driving force for planetary change. While the formalization of this epoch remains ongoing with debates regarding the exact start date © XXXX American Chemical Society
Figure 1. The Scream by Edvard Munch. Received: August 13, 2018
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DOI: 10.1021/acs.est.8b04534 Environ. Sci. Technol. XXXX, XXX, XXX−XXX
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Environmental Science & Technology
is to find a way to investigate the culmination and complexities of all human-driven impacts on the environment and biota. Kramm et al., recently suggested “complexity is the new normal”,12 but perhaps more accurately complexity is now being recognized as normal. If such a notion is accepted, then the next question becomes how to change our discipline from one which has traditionally focused on single pollutant−organism interactions and more recently on multiple defined stressors, to one that encompasses an entire system that undergoes constant fluctautions. Here there are no easy answers, but the first step is to recognize the challenges ahead, and to engage with other disciplines and improve communication within and between different fields. Moreover, we must acknowledge that the answers may not lie within our existing research methodologies, but that we may need to embrace new technological advances and seek disruptive solutions.13 Ecotoxicology should not be sidelined from the dialogue of the Anthropocene. The words of Edvard Mucnch “infinite scream of nature” have become extremely prescient in the Anthropocene. Are ecotoxicologists ready to hear this plea?
between stressors, both chemical (i.e., other pollutants) and nonchemical (i.e., human-driven fluctuations in natural conditions).
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MULTIPLE STRESSORS VS A SYSTEM IN FLUX The traditional approach in ecotoxicology has seen representative organisms exposed to single chemical stressors under stable conditions. Although valuable from the viewpoint of reporting toxicities and determining mechanisms and modes of action, this approach has been criticized as reductionist7 and essentially distills the complexities of real-world exposure scenarios into simplistic single stressor laboratory tests. The recognition that pollutants do not exist in isolation has led to the multiple stressor approach in which pollutants are combined and studies in which pollutants are combined with natural (nonchemical) stressors that reflect the varying environmental conditions. Yet here I postulate that the multiple stressor exposures do not go far enough as only a defined set of stressors are tested and varied. The challenge of the Anthropocene is to study ecotoxicological impacts without identifying each individual stressor. In so doing, ecotoxicology must recognize that the number of potential stressors acting simulataneously and their interactions is vast and incalculable. Instead it may be time to view the environment as a system in a state of constant flux in which potential impacts of an individual pollutant are governed by three sets of interactions: 1. The interaction with other chemical entities 2. The interaction with human-driven changing climatic conditions 3. The interaction with biota whose baseline physiology and behavior are changing in response to anthropogenic pressures While the first two of these interactions are relatively well studied with multiple stressor approaches, it is the third interaction that is most often overlooked. Yet environental pressures can alter the behaviors and physiology of biota resulting in a change in susceptibility to pollutants effects.8,9 Thus, when considering the environment as a temperemental fluctuating system, the importance of the biological component must not be disregarded.7
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. ORCID
Farhan R. Khan: 0000-0002-9251-2972 Notes
The author declares no competing financial interest.
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REFERENCES
(1) Heller, R. Edvard Munch: The Scream; Viking Press: New York, 1973. (2) Steffen, W.; Rockström, J.; Richardson, K.; Lenton, T. M.; Folke, C.; Liverman, D.; Summerhayes, C. P.; Barnosky, A. D.; Cornell, S. E.; Crucifix, M.; et al. Trajectories of the Earth System in the Anthropocene. Proc. Natl. Acad. Sci. U. S. A. 2018, 115, 201810141. (3) Crutzen, P. J. Geology of mankind: the anthropocene. Nature 2002, 415, 23. (4) Steffen, W.; Broadgate, W.; Deutsch, L.; Gaffney, O.; Ludwig, C. The trajectory of the Anthropocene: The Great Acceleration. Anthropocene Review 2015, 2, 2053019614564785. (5) Steffen, W.; Richardson, K.; Rockström, J.; Cornell, S. E.; Fetzer, I.; Bennett, E. M.; Biggs, R.; Carpenter, S. R.; de Vries, W.; de Wit, C. A.; Folke, C.; Gerten, D.; Heinke, J.; Mace, G. M.; Persson, L. M.; Ramanathan, V.; Reyers, B.; Sörlin, S. Planetary boundaries: Guiding human development on a changing planet. Science 2015, 347, 1259855. (6) Egeghy, P. P.; Judson, R.; Gangwal, S.; Mosher, S.; Smith, D.; Vail, J.; Hubal, E. A. C. The exposure data landscape for manufactured chemicals. Sci. Total Environ. 2012, 414, 159−166. (7) Segner, H.; Schmitt-Jansen, M.; Sabater, S. Assessing the impact of multiple stressors on aquatic biota: the receptor’s side matters Environ. Environ. Sci. Technol. 2014, 48, 7690−7696. (8) Noyes, P. D.; McElwee, M. K.; Miller, H. D.; Clark, B. W.; Van Tiem, L. A.; Walcott, K. C.; Erwin, K. N.; Levin, E. D. The toxicology of climate change: Environmental contaminants in a warming world. Environ. Int. 2009, 35, 971−986. (9) Hartl, M. G. Fish Ecotoxicology in a Changing World: do we Need New Biomarker Endpoints in Light of Climate Change? Journal of Fisheries Sciences.com 2015, 9, 49. (10) Burton, G. A., Jr. Stressor exposures determine risk: So, why do fellow scientists continue to focus on superficial microplastics risk? Environ. Environ. Sci. Technol. 2017, 51, 13515−13516.
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RECOGNIZING THE CHALLENGE AHEAD The challenge for ecotoxicologists is to change the way in which we conduct the majority of our research; specifically the focus on single stressors must be replaced by a more holistic vision. Currently, much attention is placed on the environmental presence and potential toxicological effects of microplastics (MPs). While recognized as unsightly, debate rages on toxicity of MPs with some authors suggesting the risks of MP exposure have been overblown10 whereas others see MPs as a marker of the Anthropocene. Indeed plastic debris is one of the potential stratographic layers that may be used to date the advent of transition of Holocene to Anthropocene.11 However, the attention on this pollutant or any single pollutant belies the realities of the Anthropocene in which stressors are all acting simulataneously. Thus, no single contaminant can or should be designated as being representative of the Anthropocene. Ecotoxicology as a whole must move away from the study of the “toxicants du jour”, the hot topics: microplastics today or nanoparticles prior to that. Instead the environmental challenge in this time frame (perhaps as it has always been) B
DOI: 10.1021/acs.est.8b04534 Environ. Sci. Technol. XXXX, XXX, XXX−XXX
Viewpoint
Environmental Science & Technology (11) Zalasiewicz, J.; Waters, C. N.; do Sul, J. A. I.; Corcoran, P. L.; Barnosky, A. D.; Cearreta, A.; Edgeworth, M.; Gałuszka, A.; Jeandel, C.; Leinfelder, R.; McNeill, J. R. The geological cycle of plastics and their use as a stratigraphic indicator of the Anthropocene. Anthropocene 2016, 13, 4−17. (12) Kramm, J.; Völker, C.; Wagner, M. Superficial or Substantial: Why Care about Microplastics in the Anthropocene? Environ. Sci. Technol. 2018, 52, 3336−3337. (13) Sedlak, D. L. Disruptive Environmental Research. Environ. Sci. Technol. 2018, 52, 8059−8060.
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DOI: 10.1021/acs.est.8b04534 Environ. Sci. Technol. XXXX, XXX, XXX−XXX
