Climate Change and Plants, historic and future uncertainties.....

Historically, plant species have adapted to climate change by moving to seek ways to survive within their optimal environmental envelope.  Pollen records from sediment cores have become important biological proxies of the rapid climate shifts during Pleistocene glacials, interglacials and stadials, supporting ice core and deep ocean proxy records. 

The Carp Lake, Washington, U.S. pollen record below dates 130,000 years and is of high resolution. 

CARP LAKE POLLEN RECORD - note absence of oak during LGM

Whitlock, C. and Bartlein, P. J. (1997)
 

During Last Glacial Maximum 18,000-20,000 years ago at Carp Lake, there was an increase of evergreens with an expansion of spruce in the late glacial but hemlock and cedar did not increase though there was an increase of sagebrush (Artemisia).This was a sagebrush/steppe environment, relatively cool and dry, not significantly wetter than the present.  There was a big shift at 80,000 years ago, a warmer isotope 5 period when oak came in. 

Current research suggests that in our rapidly warming 21st century, plants may be forced to move in excess of 1 km per year to keep up with the changing climate, according to Corlett and Westcott (2013)  In this article , the authors state that many plants will not be able to move fast enough to adapt with consequences for biodiversity and carbon storage.

Although ongoing research over the past 40 years is slowly elucidating historical patterns of past vegetation, there is still ongoing debate of many details of glacial refugia.  In order to have any pollen record, a sediment core from an anoxic sedimentary lake is required, lakes which in many arid parts have dried up.  Additionally, during the LGM,  many areas were cool and dry with minimal rain and low CO2 levels.  P. C. Tzedakis, B. C. Emerson and G. M. Hewitt (2013)believe there was an absence of temperate trees north of 45 degrees N and a west-east asymmetry in boreal tree distribution with a treeless Western Europe north of 46 degrees N, while restricted boreal populations persisted in Eastern Europe to 49 degrees N and higher latitudes east of the Fennoscandian ice-sheet. 

 

In future decades, vegetation will no doubt struggle to adapt to climate change within a certain climatic envelope but challenges will emerge from insects and new pathogens responding aggressively to a warming world.  Anyone who has visited the wet and humid Amazon rainforest will confirm that insects are not only bigger, they are more aggressive.  According to researchers at Exeter University, since 1960, viruses, nematode worms and any number of insects have been moving north at 3 km per year, posing a gradually increasing threat to global food supplies. Fisher et al. (2012)

 

 

Obviously we must be diligent as we work towards mitigation in our climate changing world.