Climate change, impacts and vulnerability in Europe ... - MemoFin.fr

Climate impacts on socio-economic systems and health4.1.3 AgrophenologyRelevanceChanges in crop phenology provide importantevidence of responses to recent regional climatechange (Menzel et al., 2003). Although phenologicalchanges are often influenced by managementpractices, in particular sowing date and choiceof cultivar, recent warming in Europe has clearlyadvanced a significant part of the agriculturalcalendar. Specific stages of growth (e.g. flowering,grain filling) are particularly sensitive to weatherconditions and critical for final yield. The timingof the crop cycle (agrophenology) determinesthe productive success of the crop. In general, alonger crop cycle is strongly correlated with higheryields, since a longer cycle permits better use of theavailable thermal energy, solar radiation and waterresources.Past trendsChanges in the phenological phases of severalperennial crops in Europe, such as the advance in thestart of the growing season of fruit trees (2.3 days/10years), cherry tree blossom (2.0 days/10 years)and apple tree blossom (2.2 days/10 years), in linewith increases of up to 1.4 °C in mean annual airtemperature have been observed in Germany during1961–2000 (Chmielewski et al., 2004). Sowing orplanting dates of several agricultural crops havebeen advanced, for example by 5 days for potatoesin Finland (1965–1999), 10 days for maize and sugarbeet in Germany (1961–2000) and 20 days for maize inFrance (1974–2003) (IPCC, 2007).An analysis of the modelled flowering date forwinter wheat in Europe between 1975 and 2010shows a general and clear increasing trend, whichis most pronounced in north-western Europe(Map 4.2). In parts of Europe the modelled floweringdate has advanced by 0.3–0.5 days per year. Thismodelled advance in flowering date probablyexceeds what is observed in reality, as day lengthresponses in the plants and farmers' choices ofcultivars with longer growth duration will reducethis response.ProjectionsWith the projected warming of the climate inEurope, further reductions in the number of daysrequired for flowering in cereals and maturity maybe expected throughout Europe (Map 4.3). Themodelled changes in flowering dates in Map 4.3include the expected effects of changes in cultivarchoice on flowering and maturity dates. Sincemany plants (including cereals) in Europe requirelong days to flower, the effect of warming on dateof flowering is smaller than would otherwise beexpected. The flowering date for winter wheat isprojected to show the greatest advance in westernparts of Europe, but with a large uncertainty dueto uncertainty in the underlying climate changeprojections. The advance in maturity date is largerthan the advance in flowering date, leading to ashortening of the grain filling period, which willnegatively affect yields. An independent studywith a different phenology model and other climatechange projections found similar advances inflowering date for winter wheat for England andWales (14–16 days by 2050) (Semenov, 2009).Key messages: 4.1.3 Agrophenology• Flowering of several perennial crops has advanced by about two days per decade in recent decades.• Changes in timing of crop phenology are affecting crop production and the relative performance ofdifferent crop species and varieties.• The shortening of crop growth phases in many crops is expected to continue. The shortening of thegrain filling phase of cereals and oilseed crops can be particularly detrimental to yield.162 Climate change, impacts and vulnerability in Europe 2012