Introduction

A predicted response of many plant species to global warming is migration to higher elevations. Likewise, rising temperatures may force small-scale farmers to shift their cultivation of specific crops to higher, cooler elevations. However, in both cases these migrations may not be required if plants can tolerate higher temperatures, or migrations may be prevented if there are other factors such as changes in soil conditions that make the upslope areas unsuitable.



Objectives and Methods

We conducted two sets of experimental transplant studies along elevation gradients in the Peruvian Andes to explicitly simulate the potential contrasting responses of natural vegetation (Weinmania bangii – a dominant Andean forest tree species) and subsistence crops (several traditionally grown varieties of potato and maize) to global warming: (a) ‘upward migration’, in which case plants were grown at their current elevation/temperature but in soils transplanted from higher, cooler elevations, and (b) ‘no migration’, in which case plants were transplanted downslope along with their home soils into warmer areas. For W. bangii, we replicated the transplant experiments with populations from the upper/leading edge, middle and lower/trailing edges of the species’ elevational/thermal range to assess the influence of local adaptation on responses to changes in temperature and soil.



Results

In the case of the crops, maize production declined markedly in response to new soil conditions and production of maize and potatoes declined by ca 90% when plants were grown under hotter temperatures, mainly because of the greater incidence of novel pests. In the case of natural vegetation, we found that seedling survival and growth of W. bangii were not affected by changes in soil conditions, regardless of the origin population. However, warming did result in decreased seedling survival; specifically, a simulated warming of 1°C caused a significant reduction in the survival of W. bangii seedlings transplanted from the mid-range population, and 2°C warming caused a severe decrease in the survival of seedlings transplanted from both the mid-range and lower-edge populations.



Implications

These findings reveal that climate change is a real and imminent threat to natural Andean ecosystems, as well as to local small-scale agriculture and food security. There is a pressing need to develop effective management strategies to mitigate the effects of global warming to help prevent the loss of native tree species and reduce agricultural yield losses.