A team of more than 100 scientists has assessed the impact
of global warming on thousands of tree species across the Amazon to discover
the winners and losers from 30 years of climate change. Their analysis found
the effects of climate change are altering the rainforest's composition of tree
species but not quickly enough to keep up with the changing environment.
The team, led by University of Leeds in collaboration with
more than 30 institutions around the world, used long-term records from more
than a hundred plots as part of the Amazon Forest Inventory Network (RAINFOR)
to track the lives of individual trees across the Amazon region. Their results
found that since the 1980s, the effects of global environmental change --
stronger droughts, increased temperatures and higher levels of carbon dioxide
in the atmosphere -- has slowly impacted specific tree species' growth and
mortality.
The ecosystem's response is lagging behind the rate of
climate change. The data showed us that the droughts that hit the Amazon basin
in the last decades had serious consequences for the make-up of the forest,
with higher mortality in tree species most vulnerable to droughts and not
enough compensatory growth in species better equipped to survive drier
conditions."
The team also found that bigger trees -- predominantly
canopy species in the upper levels of the forests -- are outcompeting smaller
plants. The team's observations confirms the belief that canopy species would
be climate change "winners" as they benefit from increased carbon
dioxide, which can allow them to grow more quickly. This further suggests that
higher carbon dioxide concentrations also have a direct impact on rainforest
composition and forest dynamics -- the way forests grow, die and change.
In addition, the study shows that pioneer trees -- trees
that quickly spring up and grow in gaps left behind when trees die -- are
benefiting from the acceleration of forest dynamics.
In particular, the study found the most moisture-loving tree
species are dying more frequently than other species and those suited to drier
climates were unable to replace them.