Climate change impacts and vulnerability in Europe 2016

Climate change impacts on society
Box 5.1
Regional case studies from the MACSUR project (cont.)
The effects of climate change in the near future (2020–2030) are likely to be a rise in daily maximum temperatures in
summer of up to + 1.7 °C, a 33 % reduction of April–June rainfall and an increased frequency of storms in autumn. The
expected reduced spring rainfall will have a significant impact on rainfed pasture and the production of hay and hence on
dairy sheep farming (up to a 13 % reduction in net income). The intensive dairy cattle system will be affected mostly by
more frequent summer heat waves, resulting in up to a 6 % net income reduction because of reduced milk yield and quality,
reduced fertility and increased dairy mortality in the tourist season, when fresh milk demand is highest. A reduction in the
income from livestock farming has been projected even if currently available adaptation options are implemented. Positive
impacts of climate change are expected for rice (up to a 9 % increase in income) and winter cereals (a 2 % increase in
income), but estimates may be biased by the high sensitivity of the applied crop models to increased CO 2 concentration. The
overall net income reduction in the case study area is expected to be 2.6 %.
The adoption of maize hybrid or rice varieties with later phenology may compensate for the yield reduction due to reduced
crop cycles under higher temperatures. However, given the significant impact of climate change on livestock farming that
is expected, adaptation options should be developed far beyond adjusting current farm management. This could involve
consideration of new farming systems or new interactions between farming systems, e.g. to better ensure feed supply for
livestock under climate change. However, such changes would need to be incentivised through changes in agricultural and
rural policies.
Box 5.2 Effects of enhanced atmospheric CO 2
Plants are affected not only by changes in temperature and precipitation, but also by changes in atmospheric CO 2
concentration, which affects crop yield and quality both directly and indirectly. Plant photosynthesis is stimulated by
enhanced CO 2 in plants that have the C3 photosynthesis pathway, namely most of the crops grown in Europe, except
tropical grasses such as maize and Miscanthus, which have the C4 pathway.
The extent to which photosynthesis is stimulated and yield is increased by elevated CO 2 concentrations depends on the
crop species and growing conditions (Ainsworth and Long, 2005; Wang et al., 2011). Recent experimental results also
indicate considerable differences between crop cultivars, showing that there may be scope for exploiting genetic variation
to enhance yield under higher atmospheric CO 2 (Ingvordsen et al., 2015). The stimulation of growth under high CO 2 has
been shown to be particularly large in legumes, as the greater availability of carbohydrates in plants stimulates biological
nitrogen fixation, although this may interact with changes in climatic conditions (Vadez et al., 2011).
Higher CO 2 concentrations will reduce the stomatal conductance of all plant species, leading to reduced transpiration
and higher water use efficiency (Kruijt et al., 2008). This is of particular importance under dry conditions, where the lower
transpiration rates will delay the onset of agricultural drought and thus reduce the impact of higher transpiration rates
under warmer conditions.
The overall effect of higher atmospheric CO 2 in C3 cereal crops such as wheat is to balance the yield reduction from higher
temperatures. As a result, there may be little net yield change for wheat under modest warming levels when the beneficial
effects of elevated CO 2 are also considered (Makowski et al., 2015). The higher assimilation at elevated CO 2 leads to a shift in
the plant carbon-to-nitrogen ratio, which affects the quality of plant biomass and crop yield. The effects differ between plant
species and some of these effects may reduce the susceptibility of plants to insect pests, reducing the need for pest control,
but also reducing the quality of feed and food, e.g. through lower protein content in grain (Högy et al., 2012).
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