Transcript The impact of climate change on agriculture

The impact of
climate change on
agriculture
But before that .. a bit about
the greenhouse effect …
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Global Warming
Is this a
problem?
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Phrases we hear include …
The Greenhouse Effect
Global Warming
Climate Change
Before we look at these, there are 2 sources of
the Greenhouse Effect
the Natural Greenhouse Effect
the Enhanced Greenhouse Effect
the first being useful, the second, well who
knows?
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The Natural Greenhouse Effect
Without it, Earth would have no living
things and would be more like Venus or
Mars
This is because the temperature would be
on average 300C colder than it is
This is how it works with CO2, the major
component…
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The Natural Greenhouse Effect at
work
The Earth is covered by a blanket
of gas.
The energy from the Sun reaches
the Earth’s surface, where some it
is converted to heat energy.
Most of the heat( blue arrows) is
re-radiated towards space, but
some is trapped by the greenhouse
gases in the atmosphere.
This natural effect allows the
Earth’s temperature to be kept at
a level necessary to support life.
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The Natural Greenhouse Effect at
work
The main Greenhouse
Gas is Carbon Dioxide.
Until the last 200
years, the amount of
CO2 has remained
stable.
This is why
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But then there is the Enhanced
Greenhouse Effect
Look how this is
different!
Much more of the
heat from the sun
gets trapped in the
atmosphere
So the Earth gets
hotter
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Why is more heat getting trapped?
We are taking the stored carbon from the
ground (oil and coal and gas) and burning it
This releases the CO2 and so the main
greenhouse gas is increasing
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And that is not all
CO2 is the MAIN Greenhouse Gas, but not the only one.
Others include
Water vapour – as in clouds – think how much warmer it
is in a winter morning when the sky is cloudy?
Methane – rotting and waste material that is breaking
down gives this off, including landfill sites.
Nitrous oxide – is produced naturally by the oceans and
the rain forests, but the rising levels are caused by
production of nylon, catalytic converters in cars and
fertilizer
Halocarbons (HFC) are totally man-made and were used
in cleaning fluids and aerosols. They have now in the main
been outlawed as they were a major cause of the holes in
the ozone layer. But as they are slow to breakdown, they
will still be a GHG problem until about 2050.
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But they all present a different level of
problem
So we use Global Warming Potential (GWP) as a
measure of how much damage they cause
CO2 is the MAIN Greenhouse Gas it has GWP of 1
Methane has a GWP of 21
Nitrous oxide has a GWP of 310
Halocarbons (HFC) has a GWP of 140 to 11,700
But remember that there is much less of these
other gases than CO2 and so while they are much
more dangerous when present, there are not in
nearly such high concentrations
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So in what ways is agriculture part of
the problem?
CO2: pastoral farms emit CO2 – more meat is
being consumed in MICs, so more pigs, poultry
and cattle are being reared, so more CO2. More
machinery powered by fossil fuels are being
used as farm production becomes mechanised,
e.g. huge combine harvesters
Methane: cows in particular give out a lot of
methane, but so do rice paddy fields. Other
material left to rot will ualso produce methane
Nitrous oxide: results from the breakdown of
both organic (manure) and inorganic (oil based)
fertilizer.
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So the enhanced green house effect
drives climate change
Cooler
Enhanced
greenhouse
effect
Temperature
Warmer
Droughts
Climat
e
change
More
Storms
Winds
Unusual
events
Floods
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In Europe
UK in the 2050s
The UK is likely to get
hotter - but also much
wetter. And if the sea
level rises, parts of
East Anglia as well as
parts of the south
east could end up
under water. Winters
are likely to be
milder, reducing the
need for central
heating. But rainfall is
likely to be heavier
and more frequent increasing the risk of
floods.
Long hot summers
may boost tourism in
parts of Britain, and
http://news.bbc.co.uk/hi/english/static/in
make it possible to
grow a greater
_depth/sci_tech/2000/climate_change/evi
variety of fruit and
dence/warmer.stm
vegetables.
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Spain in the 2050s
Spain and other
Mediterranean countries
- such as Greece, Italy
and Portugal - are likely
to be the worst
affected countries in
Europe as the climate
changes. Parts of inland
southern Spain, already
arid, may turn into
virtual desert as water
shortages increase and
they lose more of their
vegetation. Summer
temperatures may be
far too hot for tourists,
even on the coast.
Forest fires - already
more frequent than they
used to be - are likely to
increase dramatically,
especially as rural land is
abandoned.
In Europe
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Europe's rainfall
in the 2050s
Winters are likely
to get much
wetter, especially
in Scandinavia where
precipitation could
go up by as much
as 25% by the
2050s.
Mediterranean
countries will see
little difference
in winter rainfall,
but they are likely
to be much drier
in the summer.
In Europe
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Europe's rainfall in
the 2080s
Heavy winter
downpours and
flooding are likely to
become more common
across most of
Europe by the 2080s.
Precipitation could go
up by more than 30%
across most of
Scandinavia, while in
part of northern
Italy it may rise by
more than 50%.
During the summer,
on the other hand,
southern Europe is
likely to get much
drier.
In Europe
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While temperature rise is what we hear
about….
… it is rainfall change that will have more effect.
Those area that become drier will be unable to grow as
much without irrigation – and currently, much irrigation
practice is highly wasteful and can bring long-term
damage to the soil.
Extreme events are another cause of concern – unusually
heavy storms or unexpectedly long periods without
precipitation or unexpected heat-waves.
These all give challenges to agriculture that reduced the
production temporarily – challenges the idea of food
security.
Then global warming causes icecap and glacier melt that
create rising sea levels and loss of good agricultural land
to salt marsh.
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Temperature – In mid to high latitudes moderate warming may
benefit cereal crop and pasture yields, but in seasonally dry and
tropical regions even slight warming decreases yields.
Precipitation – Rainfall plays a critical role in year to year
variability of crop yield. Broadly speaking, precipitation is expected
to increase in high latitudes and decrease at mid to low latitudes
although there is high regional and seasonal variation in the level of
certainty in these projections
Extremes – Changes in the frequency and intensity of extreme
weather events will have significant consequences for agriculture.
Increases in extreme temperature events can have high impacts on
crop yields and heat stress in cattle. Increasing occurrence of
drought is projected for many important agriculture regions.
Extreme rainfall and flooding may also have severe consequences
for agriculture at the local scale and can effect grain quality as well
as quantity.
Water Resources – Large areas of agriculture exists in catchments
dominated by snow and glacier melt. Climate change will shift the
seasonality of water availability in these areas causing earlier and
more intense runoff. The increase in water at this time of year may
confer no benefits to agriculture however, if there is insufficient
storage capacity.
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Tropical storms and Sea Level Rise –Climate change is projected
to decrease frequency but increase intensity of tropical storms,
although this is highly uncertain. Sea level is set to rise as a
consequence of increasing global temperatures. Both will increase
the vulnerability of coastal and low lying agricultural areas to
factors such as coastal inundation, soil salinisation and intense
rainfall.
CO2 Fertilization – Evidence suggests that total crop and pasture
yield may rise when averaged across the globe due to effects of
CO2 fertilization, which is expected to offset negative impacts of a
changing climate. The accuracy of these projections and thus future
food security depend critically on the magnitude of the CO2
fertilization effect under actual growing conditions. Elevated CO2
is thought to decrease grain quality.
Indirect Climate Impacts: Ozone – Physiological damage to crops by
increased ground-level concentrations of ozone (O3) reduces yield.
O3 concentrations are projected to rise significantly due to
anthropogenic pollution especially in Asia.
Pests & Pathogens – Rising temperatures may alter the frequency
and intensity of pest and pathogen outbreak. However, crop/ pest
interactions are complex and poorly understood in the context of
climate change.
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Summary
The enhanced greenhouse effect can bring about climate
change
While CO2 is the major cause, methane, nitrous oxide
and HFCs also contribute.
Farmers are not innocents in this process but add to the
GHGs themselves
Climate change is having a variety of impacts on the
world:
Rising temperatures in many places
Changing precipitation patterns, with some places getting wetter
and some drier
Extreme events: high winds, heavy rain, drought
Rising sea level brought on by melting icecaps and warming
oceans
Rising levels of CO2 which may in some circumstances improve
crop yields.
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Summary
The impacts on farming without action are
mostly negative:
Hotter and drier places will produce less
As in these places the soil will become poorer
Places liable to saltwater flooding will become
unproductive.
Warmer and wetter places are more likely to suffer
from disease, lowering the yield.
But
Places in the higher latitudes (nearer the poles) are
getting a longer growing season and so can produce
more and different things than they have managed
before.
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