FURTHER READING
y
t
i
s
r
e
v
i
d
Bio
& in Singapore
BY Professor Richard Corlett
LAYOUT: JEAN LIM
According
to
NASA,
the
year 2010 was the warmest
on record and the top ten
warmest years have all been
since 1998. The reasons for
this global warming are now
well understood.
The main driver is increasing
concentrations of the socalled ‘greenhouse gases’
(carbon dioxide, methane,
nitrous oxide and others),
which absorb and re-emit
infrared radiation.
Part
of
the
re-emitted
radiation warms the earth’s
surface and lower atmosphere,
producing the observed rise in
global temperatures and changes in almost all other aspects of
climate, including rainfall.
Singapore is taking climate change very, very seriously. The
island is already measurably warmer than it was a generation
ago, and larger increases are expected in coming decades.
In 2010, the National Climate Change Secretariat (NCCS) was
established as an agency in the Prime Minister’s Office to
coordinate all aspects of Singapore’s response to global
climate change.
The agency’s website (www.nccs.gov.sg) reports the findings of
a recent study suggesting that, by 2100, average temperatures
in Singapore will have increased by 2.7-4.2 oc.
Rainfall is a whole lot harder to predict, and the best we can
say at present is that it will get wetter, or drier, or stay the
same! The NCCS is collaborating with the UK Met Office’s Hadley
singapore
No 122 37
Centre to enhance Singapore’s
climate science capabilities and,
hopefully, produce more accurate
and comprehensive predictions
for the future. Accuracy will
continue to be limited, however,
by uncertainties surrounding
future trends in global emissions
of greenhouse gases.
This article is not about climate
physics, however, but biology:
more specifically, it is about the
likely responses of animal and
plant species in Singapore to
the predicted 2.7-4.2oc increase
in temperature.
With a few striking exceptions,
such as people and urban
pigeons, most species on our
Source: National Geographic
38 singapore
No 122
planet occupy only a small
part of it, within limits set by
unsuitable climates.
The range of climates each
species can tolerate is known as
its ‘climate envelope’. The word
‘envelope’ here refers not to
the flat packets you put letters
in, but to the more general
meaning of ‘a container’, since
the climate envelope contains
the species.
If you walk up Mount Kinabalu or
travel overland from Singapore
to Thailand, you will see species
drop out as their climatic
tolerances are exceeded (i.e. it
becomes too cold or too dry),
and other species appear that
can tolerate these conditions.
But even if you stay in Singapore
for the rest of your life, the
climate will change. How will
species react?
If the changes stay within the
climate envelopes of local
species then the impacts will
probably be small. Plants may
flower less or flower more, birds
may breed at a different time of
the year, and some wild species
may increase or decrease their
populations, but the overall
impact will not be huge.
It is currently thought, although
with rather little scientific
evidence, that a temperature
rise of 1-2oc or a rainfall change
of plus or minus 20% may be
tolerated in this way.
Singapore is expecting bigger
changes than this, however, at
least in temperature. If it rises by
3-4oc, as currently seems likely,
then the thermometer may reach
40oc on hot days and fall to only
27-28oc at night.
Some parts of Asia, such as
Western
India,
experience
temperatures like this today,
but nowhere combines these
temperatures with the yearround rainfall and high humidity
that Singapore will probably
continue to have in the future.
To put it another way, by 2100,
Singapore will have a climate that
exists nowhere on Earth today.
This novelty makes it especially
hard to predict the impacts on
plants and animals, but we can
identify several possibilities.
multiple generations, which
means that only short-lived
species, such as many insects,
have the opportunity to
evolve substantially in climatic
tolerance by 2100.
Another option is to move. If
an organism moves 500 metres
up a mountain the temperature
falls by approximately 3oc, so
movement is a practical way
for a species to stay within its
current climatic envelope in a
warming world. But only if you
live on a mountain!
The summit of Bukit Timah is
only half a degree cooler than
the bottom, and there is not
much room for more species up
there anyway. Moving North (or
South) is not an option either
for most species in Singapore,
since temperatures do not get
significantly cooler until you
approach the edge of the tropics,
thousands of kilometres away.
Acclimate, adapt, move or die:
which will it be? The outcome
will certainly vary between
species, but a substantial loss of
native biodiversity in Singapore
seems likely if temperatures rise
by more than 1-2oc.
Moreover, non-native species
with
higher
temperature
tolerances will probably move
into Singapore, increasing the
pressure on the surviving native
species. Singapore is particularly
vulnerable to climate change
because it is small, more or less
flat, and already very warm.
What can we do to reduce the
impacts, not just on plants and
animals, but also on people?
Unfortunately, we cannot do
Hot Centre
Cool Periphery
First, species may acclimate to
the new climate. Acclimation
is physiological adjustment
without any genetic change
and occurs within the lifetime
of an individual organism.
I was born in London, but I
have acclimated to Singapore.
The changes in Singapore’s
climate will be gradual, which
favours acclimation, but there
are limits to any species’
acclimation capacity.
Evolutionary
adaptation
is
potentially
more
powerful,
since bigger adjustments are
possible, but evolution takes
Solar Radiation
Temperature Increase
Heat from
building surfaces
Evaporation
Evaporation
Temperature
goes down
Temperature
goes down
Heat from
vehicles
Anthropogenic
Heat
Heat from
the road surface
Lake
Forest
Urban Heat Island Effect
singapore
No 122 39
very much by ourselves. The
best possibility for local action
is to reduce the so-called urban
heat island effect, which is
responsible for making builtup areas in Singapore several
degrees warmer than the
nature reserves.
This
effect
has
several
causes, but the major one is
the gradual release of heat
stored during the day in
buildings, pavements and
roads. Increasing the density
of trees in urban areas can
help reduce this heat storage,
as can the use of green roofs
and the careful choice of
building materials.
However, achieving a degree
or so reduction in urban
temperatures is probably the
best we can hope for, and
this will not cool the nature
reserves where most of our
wild species live.
The only real answer is to
stop global warming and this
requires global collaboration.
Singapore must do its part by
reducing its own greenhouse
gas emissions, but it can
have a much bigger impact by
becoming a model for energy
efficiency that other countries
will follow.
Coordinating
Singapore’s
domestic and international
policies, plans and actions on
climate change is the job of the
NCCS, but every one of us can
help by reducing our personal
‘carbon footprint’ - the several
tonnes of carbon dioxide
40 singapore
No 122
Illustrations:
1. This graph from NASA shows the change in global surface
temperature since 1880 relative to the average temperature
for 1951-1980. The green bars represent the uncertainty in the
measurements.
2. The concentration of carbon dioxide in the atmosphere has
been measured since 1958 at the Mauna Loa Observatory on the Mauna Loa volcano in Hawaii.
emissions per year that we are
each responsible for.
burning factories in China or
farms in Malaysia.
Some of this is obvious, like
the fossil fuel burned for
our air conditioning and
transport, but much of our
personal contribution to global
warming is hidden in things
that we import from fuel-
Bottom-up through individual
action and top-down through
an
enforceable
global
agreement: climate change
can be beaten.