Edition 5, June 2010
Weeds Beat Thoreau's Natives In Resetting Their Climate Change Clock
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June 18th, 2010
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| Henry David Thoreau. | |
In the Concord woods of Massachusetts, where conservationist and writer Henry David Thoreau assiduously recorded natural history 150 years ago, weeds are responding to climate change more rapidly than native plants by dramatically adjusting their flowering time.
Since Thoreau’s time, the mean annual temperature in the area has increased 2.4 °C and invasive species are now flowering on average 11 days earlier than native species and nine days earlier than non-invasive non-native species.
Invasive species are significantly better at tracking seasonal temperatures than native species.
According to Charles Wills and co-researchers, who analysed data collected in the woods by Thoreau and subsequent naturalists, climate change is hastening invasion and weeds will increasingly dominate the area.
In an earlier paper the same research group warned that climate change “appears to have had a dramatic role in shaping the contemporary composition of the Concord flora”.
Of the plant species recorded by Thoreau, 27% have been lost from the woods, another 36% have declined and are also likely to be lost. This despite the fact that 60% of all natural areas in Concord are undeveloped or well protected.
The researchers found that changes in native plant abundance strongly correlated with flowering-time response. Species that do not respond to temperature changes have decreased greatly in abundance.
This dropoff has been particularly high in particular plant groups, including asters, bladderworts, buttercups, dogwoods, lilies, louseworts, mints, orchids, saxifrages, and violets.
The responsiveness of species to climate change is likely to be critical to their success – for example, their capacity to flower earlier to coincide with the arrival of pollinators and to time leaf emergence to maximise nutrient acquisition and light availability.
Species that can “leaf out” earlier in warmer years might shade out less responsive species, and those that can delay leaf emergence in cold years might avoid late frosts that could damage their leaves.
The researchers suggest that the worsening of weed impacts under climate change will be more pervasive than other global change factors that act more regionally, such as increasing nitrification, habitat disturbance, and underground microbial species composition.
References
Willis CG, Ruhfel BR, Primack RB, Miller-Rushing AJ, Losos JB and Davis CC. 2010. Favorable Climate Change Response Explains Non-Native Species' Success in Thoreau's Woods. Plos One 5(1).
Willis CG, Ruhfel B, Primack BR, Miller-Rushing AJ, Davis CC. 2008. Phylogenetic patterns of species loss in Thoreau’s woods are driven by climate change. Proc Nat Acad Sci USA 105: 17029–17033.