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Bioclimatic modelling: linking
biodiversity and climate science
Dr Ahmed Djoghlaf, Executive Secretary; Jaime Webbe, Programme Officer;
Annie Cung, Programme Assistant, Convention on Biological Diversity
B
iodiversity is the term given to the variety of life on Earth –
plants, animals andmicrorganisms. Biodiversity also includes
genetic differences within each species and the variety of
ecosystems such as deserts, forests, wetlands, mountains and agri-
cultural landscapes. In each ecosystem living creatures, including
humans, form a community, interacting with one another and with
the air, water and soil around them. We depend on biodiversity
to live. Indeed, ecosystem services provide us with food, clean air,
drinking water, raw materials, medicines and many other benefits.
Many human activities threaten biodiversity. According to the
Millennium Ecosystem Assessment, the main drivers of biodiversity loss
include habitat change, climate change, invasive alien species, overexploi-
tation and pollution.
1
Moreover, these drivers are either steady, show no
evidence of declining over time, or are increasing in intensity. Therefore,
changes in biodiversity are projected to continue, or accelerate.
Observed changes in climate have already had significant impacts
on biodiversity and ecosystems, including changes in species distribu-
tions, population sizes and timing of reproduction or migration events.
Observed impacts include coral bleaching, wetland saliniza-
tion, expansion of arid and semi-arid lands at the expense
of grasslands and acacia, poleward and upward shifts in
habitats, replacement of tropical forests with savanna in
the Amazon Basin and Mexico, and shifting desert dunes
– particularly in Northern and Southern Africa.
By the end of the 21st century, climate change and its
impacts could become the dominant direct driver of biodi-
versity loss. According to the Fourth Assessment Report of
the Intergovernmental Panel on Climate Change (IPCC),
2
approximately 20 to 30 per cent of plant and animal species
assessed so far are likely to be at a higher risk of extinction if
increases in global average temperature exceed 2
o
C to 3
o
C
above pre-industrial levels.
3
For example, a 51 to 65 per
cent loss in the area of the Fynbos biome of South Africa is
projected by 2050.
4
To assess the impacts that the predicted changes in
climate will have, scientists turn to a variety of modelling
approaches. Due to the complexity of natural systems,
predictive modelling is limited. Moreover, different model-
ling approaches have a varying degree of accuracy and yield
a range of conclusions. The types of models used in a study
can have important effects on the predicted impacts on
biodiversity. However, suchmodels can provide a good first
approximation of the potential impacts of climate change.
Nevertheless, model results should not be interpreted
without due consideration of their limitations.
Bioclimatic models: linking science and policy
Attributing changes in biodiversity to climate change is
complex because a number of non-climatic influences also
affect it. However, recent studies analysingmore than 1,700
species show that recent biodiversity trends match climate
change predictions, including range shifts towards the poles
and advancement of spring events.
5
Modelling strategies for predicting the potential impacts
of climate change on biodiversity often focus on the iden-
tification of a species’ bioclimatic envelope. This can be
determined by correlating current species distributions
with climate variables, or through an understanding of
species’ physiological responses to climate changes. After
having identified a species’ bioclimatic envelope, scenarios
of future climate change can be applied to assess the enve-
lope redistribution.
6
A recent analysis using bird species’
observed range shifts and climate change scenarios provided
O
bserving
, P
redicting
and
P
rojecting
C
limate
C
onditions
Ho Chi Minh City, Vietnam. Changes in the climate impact biodiversity and thereby
affect the ability of ecosystems to deliver goods and services for human well-being
Image: Mathieu Rossier