The impact of climate change on agriculture But before that .. a bit about the greenhouse effect …

Global Warming Is this a problem?

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?

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…

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.

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

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

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

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.

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

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.

So the enhanced green house effect drives climate change These affect agriculture Cooler Temperature Climate change Winds Warmer Unusual events Droughts More Storms Floods

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/sci_tech/2000/climate_change/evidence/warmer.stm

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.

In Europe 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 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.

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.

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.

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.

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.

Summary The impacts on farming without action are mostly negative: But 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.

The Impact of climate change on agriculture QUESTIONS What is the natural greenhouse effect, and how does it work? What would the earth be like with no greenhouse effect? Where does the earth get its energy? What is the name of the main Greenhouse gas? What does the symbol CO2 stand for? List the four other greenhouse gases.

QUESTIONS CONTINUED Why is more heat getting trapped in our atmosphere? What is Global Warming Potential, and how is it used? In what ways is agriculture part of the global warming problem? How does the enhanced greenhouse effect drive climate change? What are some possible solutions to help lesson the greenhouse effect? (Google it)