4.3 Agricultural land

It is estimated that the growing season has lengthened by nearly eleven days since the 1960’s. In Northern Europe leaves emerge six days earlier in the spring and they last five days longer in the autumn.

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Birds and insects strugge to adapt to a rapidly changing climate. Photo: Å. Bjørke

Other changes are plants growing at higher altitudes in the mountains, and birds lay eggs earlier in the spring.

Butterflies have extended their range northwards in Europe as well as in North America .

Migratory birds arriving  in the spring may find that they arrive too late for their tradtitional access to food, since flowering in some cases may start weeks earlier than nature has adapted to for the last millennia.

Carbon dioxide has a fertilizing effect

Increased CO2 in the air has a fertilizing effect on many plant species.

With moderate temperatures, long-term doubling of current ambient CO2 under field-like conditions leads to a 30% enhancement in the seed yield of rice, despite a 5-10% decline in the number of days to heading.

The grain yield of CO2 -enriched rice shows about a 10% decline for each 1°C rise above 26°C. This decline is caused by a shortening of growth duration and increased spikelet sterility. Similar scenarios have been reported for soybean and wheat.” (TAR, Chapter 5 )

What happens with an increase in temperature of e.g. 2°C. ?

Increasing temperatures will likely affect major crops such as tea and coffe production in East Africa

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Developing countries, whose economies often rely heavily on one or two agricultural products, are especially vulnerable to climate change. This graphic shows that with an increase of only 2 degrees Celsius, there would be a dramatic decrease in the amount of land suitable for growing Robusta coffee in Uganda. Author: Otto Simonett, UNEP/GRID-Arendal

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Major impacts on food production will come from changes in temperature, moisture levels, ultraviolet (UV) radiation, CO2 levels, and temperatures may cause expansion of production into higher elevations.

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Rice paddies in terraces, Nuwara Eliya, Sri Lanka. Rice is a crop vulnerable to global warming. Photo: Å. Bjørke

The grain filling period may be reduced as higher temperatures accelerate development, but high temperatures may have detrimental effects on sensitive development stages such as flowering, reducing grain yield and quality.

Crop water balances may be affected through changes in precipitation and other climatic elements, increased evapotranspiration, and increased Water Use Efficiency (WUE) resulting from elevated CO2.

Plant water use efficiency (WUE) is a key issue in semiarid areas, where crop production relies on irrigation. To secure environmental sustainability and food production, a better WUE is necessary. Global warming will as a rule mean increases in temperature, longer periods of drought and the risk of violent floods in semiarid regions. An improved, integrated water resources management is urgently needed in many areas.
Staple crops such as wheat and corn that are associated with subtropical latitudes may suffer a drop in yield as a result of increased temperature, and rice may disappear because of higher temperatures in the tropics

It is suggested that major changes in farming systems can compensate for some yield decreases under climate change, but additional fertilizer, seed supplies, and irrigation will involve extra costs, and threaten smallscale and subsistence farming.
IPCC:  Ecosystems and Their Goods and Services

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Increased pressure from its surroundings is threatening the Amboseli National Park, The park has been established in Kajiado District, Rift Valley Province in Kenya, and is 39,206 hectares (392 km2) in size at the core of an 8,000 square kilometres ecosystem that spreads across the Kenya-Tanzania border. The local people are mainly Maasai, but people from other parts of the country have settled there attracted by the successful tourist-driven economy and intensive agriculture. Photo: P. Prokosch

Land degradation accelerates due to increasing pressures of agricultural and industrialised livestock production, urbanization, deforestation, and extreme weather events such as droughts and coastal surges which salinate land. Instead of increasing cropland areas and making them more resilient, we degrade and reduce these areas.

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Home
Chapter 3 3. Impacts
Chapter 4 4. Ecosystems
4.1 Ecosystems and energy flow
4.2 Forests
4.3 Agricultural land
 4.4 Oceans
Chapter 5 5. Green economy

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