Learning from the past: adventures in paleo

“Without consideration of the time perspective available from the geological record, a full evaluation of the contemporary extinction problem may prove as difficult as would be the case…if an epidemiologist were to treat an infectious disease without medical records” 

(Raup, 1988, quoted in Myers, 1990)

As I’ve mentioned before, there is a consensus amongst many scientists today that we are in the early stages of a new mass extinction which unprecedented in some ways (mainly its principle cause) but preceded by 5 other mass extinctions in geological history, which as the quote above illustrates, could enlighten this situation for us.

Conservation tends to focus on the future on questions of how we can preserve species and habitats for subsequent generations, but many scientists propose that we are in the eye of the storm of biodiversity loss and therefore looking at paleoenivronmental studies offers us a long term view and a record of previous climate changes. Looking at the past may be just as important as the future. Studies further suggest that there could will be similarities between the current extinction episodes and previous ones – such as a preferential loss of endemic species and higher vulnerability of habitats in the tropics (Myers, 1990).

There are 4 key things we can learn from paleoenvironmental studies…

1. Extinctions are not unprecedented – as Jablonski (2001) states, one of the key things that can be taken from previous events is that mass extinctions happen – species and ecosystems are not resilient forever and they are not immune to change. Over 90% of all species that have ever walked the earth are currently extinct. Fossil records reveal previous climate change events have occurred and ecosystems have persisted and adapted to this (Jablonski, 2004)
2. Ecosystems have the power to recover – each past mass extinction has been followed by a period of recovery in which new species have evolved at a rapid rate. The disruptive processes driving extinction could also act as creative ones and lead to speciation (Myers 1990). Despite this hopeful prospect, it’s important to remember that it’s extremely difficult to accurately predict the evolutionary response of species and any such process will undoubtedly be a slow one, and may not be able to keep up with human intervention (Jablonski 2001).
3. Extinctions may not happen the way we expect – Past events have shown that the likelihood of a species surviving is not necessarily linked to its success during periods of low extinction rates (‘background’ periods). Therefore we won’t necessarily know which species are at highest risk from loss, stressing the importance of consistent global conservation efforts (Jablonski 2001; Myers, 1990).
4. The past can help to inform present conservation – Whist point 3 may seem to make the task of conservation impossible, there is evidence that can be taken from past extinctions to aid efforts. Past extinctions provide examples of how species have been able to adapt to prior climate events and therefore offer tips on how we can help current species to adapt. They also offer some words of caution for present-day conservation practitioners – endemic species suffered the greatest during the Cretaceous-Tertiary mass extinction (Myers, 1990), so this emphasises the attention they need in conservation efforts. Fossil pollen records show changes in forest range shifts and the joining and splitting up of forest communities, indicating a potential for movement, but Petit (2008) states that records imply that today’s trees won’t have the ability to migrate in time with future rapid warming. Petit further suggests tree species therefore may need a helping hand in the form of ‘assisted migration’ – perhaps we should be acting on this and starting to aid tree species to mitigate against warmer conditions through actively creating plantations in areas predicted to move into a suitable climate.

Of course, there remains the critical issue that the 6^th mass extinction will be unprecedented due to the major impact of homo sapiens, so prediction will remain tricky. But paleo studies may push us closer to being able to make informed decisions in conservation.