Diversity buffers winegrowing regions from climate change losses

Abstract

Agrobiodiversity-the variation within agricultural plants, animals, and practices-is often suggested as a way to mitigate the negative impacts of climate change on crops [S. A. Wood et al., Trends Ecol. Evol. 30, 531-539 (2015)]. Recently, increasing research and attention has focused on exploiting the intraspecific genetic variation within a crop [Hajjar et al., Agric. Ecosyst. Environ. 123, 261-270 (2008)], despite few relevant tests of how this diversity modifies agricultural forecasts. Here, we quantify how intraspecific diversity, via cultivars, changes global projections of growing areas. We focus on a crop that spans diverse climates, has the necessary records, and is clearly impacted by climate change: winegrapes (predominantly Vitis vinifera subspecies vinifera). We draw on long-term French records to extrapolate globally for 11 cultivars (varieties) with high diversity in a key trait for climate change adaptation-phenology. We compared scenarios where growers shift to more climatically suitable cultivars as the climate warms or do not change cultivars. We find that cultivar diversity more than halved projected losses of current winegrowing areas under a 2 °C warming scenario, decreasing areas lost from 56 to 24%. These benefits are more muted at higher warming scenarios, reducing areas lost by a third at 4 °C (85% versus 58%). Our results support the potential of in situ shifting of cultivars to adapt agriculture to climate change-including in major winegrowing regions-as long as efforts to avoid higher warming scenarios are successful.

Keywords: agriculture; agrobiodiversity; climate change adaptation; phenology; resilience.

Fig. 1.

Global maps of winegrowing. (A) Current winegrowing regions (see SI Appendix, Fig. S1 for more detail). (B) Modeled predictions of cultivar diversity (total number of varieties) under our 0 °C reference scenario—all colored pixels show areas predicted as climatically suitable (Calculating Climatic Suitability). (C–E) Predicted effects of climate change on cultivar diversity and distribution under 2 °C warming (C), 4 °C warming (D), and cultivar turnover (E; cultivar gains and losses shown simultaneously via a bivariate color scale). See SI Appendix, Fig. S13 for 4 °C turnover.

Fig. 2.

Winegrape cultivar diversity can impact the loss of current winegrowing regions (see SI Appendix, Fig. S14 for losses within all climatically suitable areas). Predictions of loss are shown for scenarios of 2 °C warming (yellow bars) and 4 °C warming (red bars) relative to a 0 °C reference scenario. Shaded areas illustrate $\pm 1$ SD around the mean loss for each number of cultivars, combining two sources of uncertainty: 1) variability according to all possible combinations of n cultivars (e.g., at one cultivar, that cultivar could be any of the 11 considered and each covers a different area), and 2) modeled climatic suitability under each climate change scenario (e.g., one model member may predict suitability of an area, while another does not). These results are based on climatic suitability calculated with all eight climate variables (Modeling Maturity).

Fig. 3.

Predicted gains (turquoise) and losses (purple) of climatically suitable growing areas for each of the 11 studied winegrape varieties (cultivars) under scenarios of 2 °C (A) and 4 °C (B) warming. To facilitate comparison of varieties and warming scenarios, we show gains and losses as the proportional change for each variety with warming (i.e., the area predicted with warming relative to the area predicted under our reference scenario of 0 °C). Gains are shown relative to both current winegrowing regions (darker turquoise) and all areas identified as climatically suitable under our reference scenario (pale turquoise). Background shading and variety name coloring differentiates red from white varieties; for each variety, we also give the total hectares predicted to be climatically suitable under our reference scenario of 0 °C within current winegrowing regions parenthetically. For a version of this figure showing gains and losses as absolute change in hectares, see SI Appendix, Fig. S23.