Omlægning til økologisk jordbrug i et lokalområde. Scenarier for natur miljø og produktion

Delprojektet om Natur- og miljøscenarier formulerede 4 måder at omlægge 25% af et konkret værkstedsområde til økologisk jordbrug. I scenariet ”Mælk” var det fortrinsvis kvægbrug, der blev omlagt. Scenariet ”1997” var også domineret af mælkeproducenter, men med et tillæg af planteavlsbedrifter. Scenariet ”Planter/svin” omfattede udelukkende svine- og planteavlsbrug, og scenariet ”Selvforsyning” omfattede bedrifter i et udpeget SFL-område, som ikke måtte supplere produktionen med indkøbt foder. Resultaterne pegede på en tendens til fald i kvælstofudvaskningen i hele området i tre scenarier, mens der var uklarhed m.h.t. det fjerde - ”Planter/svin”- scenariet. Belastningen med pesticider blev reduceret. I scenarierne ”Mælk” og ”1997”var reduktionen mindre end de forventelige 25%, mens den var 31% for svine- og plantebrug. Hvad angår jordforstyrrelser øgedes den andel af arealet, der ikke blev forstyrret med 35% og 21% i de to scenarier ”Mælk” og ”1997, mens øgningen for ”Planter/svin” var 10%, og for ”Selvforsyning” 15%. Ved omlægning af plante- og svinebrug øgedes samtidig arealet, der blev forstyrret mere end konventionelle kornafgrøder med maksimalt 6% af hele området. Udlægsmarker blev øget fra 8% af områdets samlede areal til 10 og 14% i de to mælkeproducentdominerede scenarier - og helt op til 18 og 19% af totalarealet i ”Planter/svin”- og ”Selvforsyning”-scenarierne. En særligt dybtgående analyse af lærkers levevilkår viste, at territorietæthed og produktion af unger ikke ændrede sig konsistent med omlægning fra økologisk til konventionel drift, fordi ændringer i afgrødefordeling, ophør med pesticider, intensiv græsning og mekanisk ukrudtsbekæmpelse påvirker levevilkårene såvel positivt som negativt

Agricultural experimental sites

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Application of the water and heat model to agricultural land

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Application of the nitrogen model to agricultural land

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Uncertainties in projected impacts of climate change on European agriculture and terrestrial ecosystems based on scenarios from regional climate models

The uncertainties and sources of variation in projected impacts of climate change on agriculture and terrestrial ecosystems depend not only on the emission scenarios and climate models used for projecting future climates, but also on the impact models used, and the local soil and climatic conditions of the managed or unmanaged ecosystems under study. We addressed these uncertainties by applying different impact models at site, regional and continental scales, and by separating the variation in simulated relative changes in ecosystem performance into the different sources of uncertainty and variation using analyses of variance. The crop and ecosystem models used output from a range of global and regional climate models (GCMs and RCMs) projecting climate change over Europe between 1961-1990 and 2071-2100 under the IPCC SRES scenarios. The projected impacts on productivity of crops and ecosystems included the direct effects of increased CO2 concentration on photosynthesis. The variation in simulated results attributed to differences between the climate models were, in all cases, smaller than the variation attributed to either emission scenarios or local conditions. The methods used for applying the climate model outputs played a larger role than the choice of the GCM or RCM. The thermal suitability for grain maize cultivation in Europe was estimated to expand by 30-50% across all SRES emissions scenarios. Strong increases in net primary productivity (NPP) (35-54%) were projected in northern European ecosystems as a result of a longer growing season and higher CO2 concentrations. Changing water balance dominated the projected responses of southern European ecosystems, with NPP declining or increasing only slightly relative to present-day conditions. Both site and continental scale models showed large increases in yield of rain-fed winter wheat for northern Europe, with smaller increases or even decreases in southern Europe. Site-based, regional and continental scale models showed large spatial variations in the response of nitrate leaching from winter wheat cultivation to projected climate change due to strong interactions with soils and climate. The variation in simulated impacts was smaller between scenarios based on RCMs nested within the same GCM than between scenarios based on different GCMs or between emission scenarios