Department of BIOLOGICAL SCIENCES
What
effect does climate change have on plants?
Much research has concentrated on the effect
of rising atmospheric concentrations of carbon dioxide on plants. Carbon
dioxide is used by plants to photosynthesise and is a limiting factor for
C3 plants at ambient levels. Higher concentrations of atmospheric carbon
dioxide cause an increase in photosynthesis, so long as other resources
such as nutrients and light levels are not limiting. Studies on crop species
show that with a doubling of carbon dioxide concentrations (predicted levels
of c.2050) plants will increase in biomass by 30 - 40%.
These
nasturtiums were grown under identical conditions except that the plant
on the left received ambient concentrations of carbon dioxide (360 ppmv)
and the plant on the right 750 ppmv.
As well as consistent trends towards increased
total biomass and greater water use efficiency, there are also higher
carbon to nitrogen ratios in leaves and wood, and greater leaf thickness
with lower specific leaf area. Effects on characteristics such as phenology
and biomass partitioning are more variable.
Photo J.Lake
As temperatures rise and precipitation patterns
change, many plants will find themselves in unfavourable climatic envelopes.
It is expected that most species will tend to migrate 
polewards,
or higher in elevation. Rates of migration of some plant species during
past periods of global warming or cooling have been estimated from fossil
remains and palynological studies. These suggest that the rates are slow
and may be inadequate to keep pace with current rapid warming.
Photo A.Moles
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