The history of life on Earth is punctuated by mass extinctions, which are relatively sudden events in which many or even most of the planet’s species die out. Causes of mass extinctions in Earth’s past include asteroid impacts, massive volcanic eruptions, and major climatic shifts. As greater numbers of species go extinct under a human-dominated planet, an important question worth asking is whether we are currently causing a new mass extinction.
In order to understand to what degree humans drive extinction, we need to take a closer look at how different organisms adapt, evolve and recover. One way to do this is to look at the intrinsic risk of certain organisms to go extinct under “normal” environmental variations, as discussed in a paper by Finnegan et al. (2015). Intrinsic risk is calculated for a particular group of organisms (i.e., marine mammals or corals) by identifying the diversity of species in specific areas over the past 23 million years. By mapping the distribution of genera over time, scientists can identify geographic distribution of species reduction. High intrinsic risk -- or high extinction risk -- identifies areas with fauna that are strongly affected by human activity or climate change (both natural and anthropogenic). Finnegan et al. (2015) looked at intrinsic risk for six groups of marine organisms and were able to conclude that tropical areas of the Western Atlantic and Indo-Pacific have the highest intrinsic risk. This pattern is likely driven by regional, organismal requirements requiring specific habitat and food sources for survival, which makes tropical species more vulnerable to even small perturbations in their ecosystems. The Finnegan et al. (2015) study finds marine mammals, which includes dolphins, seals, whales, and others, have the highest intrinsic risk. On the one hand, this means that significant extinctions could be expected within this group even without human activity. However, their overall extinction risk is even higher with human activity, as we cause additional stressors of habitat loss, overfishing, and pollution. Mapping geographic regions with high intrinsic risk and comparing them with areas currently experiencing extreme stress from human activities, as well as areas predicted to experience dramatic effects of human-caused climate change, gives us some sense of what to expect in the near-future. For instance, the Western Atlantic is an area with high direct human impact, whereas the Indo-Pacific is especially sensitive to future climate change. Due to the high intrinsic risk in these areas, scientists expect the overall magnitude of extinction to be particularly severe. In addition to understanding extinction, the geologic record can tell us how systems recover from abrupt change. A recent study by Moffitt et al. (2015) analysed how seafloor community ecology changed in response to episodes of climate change since the Last Glacial Maximum (20,000 years ago). Surprisingly, this study found that although seafloor communities can change very rapidly (<100 years) in response to prevailing seafloor conditions, it may take a much longer time (>1000 years) for ecosystems to recover if favorable conditions return. A sobering lesson from this study is that changes humans make to our climate and environment may have quick, lasting impacts which may not be easily reversible on short timescales. Although extinctions are a part of Earth history, on human timescales they may have devastating effects on ecosystems that we depend upon for our daily lives. The papers we explored in our class show that many of the areas to be affected by anthropogenic climate change are already predisposed to experience significant extinctions, and when extinctions do happen, it can take the lifespan of many human generations for ecosystems to recover. As a result, we have to work to conserve what we can, and also begin to think of ways to respond and adapt to extinctions that are already taking place and may be unavoidable. Conservation Paleoecology: Utilizing records of past ecosystems to inform modern management6/14/2017
Scientists can study the fossil record to learn about past ecosystems and to better inform decisions about management for the future. Conservation paleobiology is an emerging field that integrates paleontological data with current data in order to better understand how ecosystems change, including how they respond to human impacts. Paleobiological data are useful for defining the range of natural variability within ecosystems that existed prior to widespread human activity. We explored several drivers of ecosystem change and the ways in which conservation paleobiology can be utilized in understanding and responding to these changes. This week we explored the utility of conservation palaeobiology by focusing on a paper by Dietl et al. 2015 that outlines five processes that affect ecosystems and can be studied within the paleoecological record: habitat change, climate change, overexploitation, invasive species, and biogeochemical changes. For modern ecologists, it can be incredibly expensive and logistically challenging to conduct large studies for any period of time lasting longer than a year. Most graduate programs are only 4-6 years, and most grant cycles for research funds are 2-5 years with few exceptions. The palaeontological record therefore offers the advantage of observing ecosystems across longer time scales, including:
Another strength of accessing the paleontological record is that it allows for comparison with the rare but powerful long-term monitoring studies conducted by modern ecologists to put the observation of current changes in context. Furthermore, integrating paleoecological studies with studies of paleoclimate and paleoceanography (like those discussed in our other blog posts!) gives us context for the magnitude and rate of change occurring in modern ecological and climate systems. The fossil record can help us understand the timing of events, including biotic changes (e.g. the spread of invasive species), as well as abiotic factors (e.g. volcanic eruptions and gas emissions). The examination of past environmental change also allows us to separate “natural” states of climate change from human-induced environmental changes (e.g. past ocean acidification events are usually much slower than today). We developed the chart below to summarize our discussions of how studying ecosystem processes through the lens of paleoecology and paleoclimate can produce deliverable results that inform policy and management. The columns represent the major processes driving modern ecosystem change as defined by Dietl et al. 2015, and the blue boxes list the ways in which understanding these processes through the lens of paleoecology can be utilized to inform policy. To further explore this topic and to see specific examples of how paleoecological studies can provide management deliverables, see Dietl et al. 2015. To understand how long term, geologic information might be incorporated into marine conservation and management, we contacted Cyndi Dawson, at the California Ocean Protection Council, who noted, “Understanding both our recent and far past gives us the ability to understand current changes in context. We can see that the rate and magnitude of some changes we are seeing now is very different than what we have seen before. This can help us understand the drivers of change and allow us to think about ways to create informed policy that can help mitigate negative impacts to our environment.“
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ArchiveSea Levels: Past, Present and Future
How has El Niño changed in the past? Lessons from paleoclimate archives Paleoclimate into Policy: is there a bright future for learning from the past AuthorsWritten by the members of UC Davis GEL 232: K. Barclay, R. Banker, P. Edwards, C. Fish, K. Hewett, T. Hill, G. Hollyday, C. Livsey, H. Palmer, P. Shukla, D. Vasey. Categories
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