Terrestrial ecosystems regulate climate through both biogeochemical (greenhouse-gas regulation) and biophysical (regulation of water and energy) mechanisms. However, policies aimed at climate protection through land management, including REDD+ (where REDD is Reducing Emissions from Deforestation and Forest Degradation) and bioenergy sustainability standards, account only for biogeochemical mechanisms. By ignoring biophysical processes, which sometimes offset biogeochemical effects, policies risk promoting suboptimal solutions. Here, we quantify how biogeochemical and biophysical processes combine to shape the climate regulation values of 18 natural and agricultural ecoregions across the Americas. Natural ecosystems generally had higher climate regulation values than agroecosystems, largely driven by differences in biogeochemical services. Biophysical contributions ranged from minimal to dominant. They were highly variable in space, and their relative importance varied with the spatio-temporal scale of analysis. Our findings reinforce the importance of protecting tropical forests, show that northern forests have a relatively small net effect on climate, and indicate that climatic effects of bioenergy production may be more positive when biophysical processes are considered. Ensuring effective climate protection through land management requires consideration of combined biogeochemical and biophysical processes. Our climate regulation value index serves as one potential approach to quantify the full climate services of terrestrial ecosystems.