Considering tree species of the future: Tree species in Mexico predicted to have suitable current climate in the United States and Canada

Suitable climate for tree species currently located in Mexico may shift to the United States and Canada under future warming, resulting in the potential for tree species shifts, with new species gained in the USA and Canada and species losses in Mexico. To isolate dynamics, I modeled distributions of 184 commonly recorded wide-ranging or transboundary tree species of North America, including presence in Mexico, and 258 tree species primarily abundant in Mexico, including 51 endemic species, under current climate and predicted to three future climates (projected warming of 4.3–8.8 ℃ during 2071–2100 in North America). Secondarily, I identified patterns between species distributions and outcomes. Model accuracies were 0.98 for withheld samples, with coldest temperature as the most important variable. Species with distributions that were larger in area and lower in elevation (likely related to the modeling algorithm being able to locate more analogous climates) and higher in latitude (due to greater area in the northern North American continent) were more probable to expand distributions under warming temperatures. Predicted losses in suitable future climate conditions occurred for 36 of 184 wide-ranging species and 103 of 258 Mexican species. For wide-ranging species, losses occurred in Mexico and extended along the USA Gulf Coast, with gains in the western USA and Canada. For Mexican species, losses occurred south of Mexico, with gains in northern Mexico, the southeastern USA, and along the Pacific Coast from the USA to Canada. In Mexico, tree species overall continued to have suitable future climate conditions. In the USA, 38 of 184 wide-ranging species and 246 of 258 Mexican species may be gained in the future, and generally, predictions were for suitable climate conditions both now and in the future. In Canada, suitable future climate conditions for 35 of 184 wide-ranging species were predicted, of which 10 species were predicted to have suitable current climate conditions, and suitable future climate conditions for 80 of 258 Mexican species were predicted, of which 21 species were predicted to have suitable current climate conditions. Many tree species present in Mexico were predicted to already have a suitable current climate in the USA and Canada, which suggests a lag in ecosystem transition that may be addressed by current management to support biodiversity.