The impact of climate change on agriculture

1
The impact of climate change on agriculture

• But before that .. a bit about the greenhouse
  effect

2
Global Warming
Is this a problem?
3
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?

4
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

5
The Natural Greenhouse Effect at work

• The Earth is covered by a blanket of gas.
• The energy from the Sun reaches the Earths
  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 Earths
  temperature to be kept at a level necessary to
  support life.

6
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

7
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

8
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

9
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.

10
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

11
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.

12
So the enhanced green house effect drives climate
change
Enhanced greenhouse effect
These affect agriculture
Cooler
Climate change
Temperature
Winds
Warmer
Unusual events
Droughts
More Storms
Floods
13
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 make it possible to grow a greater
  variety of fruit and vegetables.

http//news.bbc.co.uk/hi/english/static/in_depth/s
ci_tech/2000/climate_change/evidence/warmer.stm
14
In Europe

• 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.

15
In Europe

• Europe's rainfall in the 2050sWinters 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.

16
In Europe

• 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.

17
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.

18
(No Transcript)
19
(No Transcript)
20

• 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.

21

• 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.

22
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.

23
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.