Crops and grass/Policy issues

Component is implemented in:

LPJmL model (version IMAGE-LPJmL 3) Components: Carbon cycle and natural vegetation Crops and grass Water

Related IMAGE components

Agriculture and land use Atmospheric composition and climate Carbon cycle and natural vegetation Carbon, vegetation, agriculture and water Land-use allocation Water

Projects/Applications

AgMIP and ISI-MIP project

Key publications

Bondeau et al., 2007 Waha et al., 2012

References

Rosenzweig et al., 2013

Flowchart Crops and grass. See also the Input/Output Table on the introduction page.

Policy issues

Climate change significantly affects crop yields, and these effects differ considerably per region and crop. Assumptions on CO₂ fertilisation strongly influence the climate change effect. Without CO₂ fertilisation, global average crop yields decline under changing climate but increase for most crops under standard assumptions on CO₂ fertilisation (the figure below). Example: Policy interventions that directly affect agricultural production systems comprise environmental regulation, such as use of fertilisers and pesticides. These interventions cannot be directly assessed by the model because of lack of explicit nutrient dynamics, no direct coverage of pest control and water quality. Instead, the model evaluates several indirect policy interventions, such as impacts of climate policy, dietary habits, trade patterns, and land-use regulation.

The effect of climate change on crop yields strongly depends on the effect of CO₂ fertilisation, also represented in LPJmL. Lines show means across several climate scenarios; adopted from Rosenzweig et al. (2014).

Climate policies focus on atmospheric CO₂ concentration levels, and affect the degree of global warming, and shifts in precipitation patterns. These factors have an impact on agricultural productivity and thus indirectly also influence land-use patterns and water requirements. The impact of climate change on agricultural productivity results from several interacting mechanisms. For instance, climate change and the associated increase in atmospheric CO₂ concentrations may increase yields in temperate regions (see the figure below) but decrease agricultural productivity in subtropical and tropical regions. As a consequence, agriculture is abandoned in some areas and expanded to other regions (the figure below). If policy interventions lead to large reductions in greenhouse gas emissions, this directly affects agricultural productivity and associated land-use dynamics (the figure below).

By the end of the century climate change impacts on crop yields under the baseline could be reduced by stringent climate policy.