Terrestrial processes control land-to-atmosphere fluxes of water, energy, and carbon and are also influenced by climate. Feedbacks in the land-atmosphere coupled system can therefore potentially modulate changes in land surface water and carbon fluxes. Prior work has focused on one specific aspect of land-atmosphere coupling modulated by soil moisture, while largely ignoring other ways in which the coupling between land and atmosphere could alter climate. We use a novel experimental design of paired perturbed parameter ensembles in an Earth system model to isolate the extent to which atmospheric feedbacks modulate the global water and carbon cycles by perturbing land parameters spanning a wide range of terrestrial processes which affect evapotranspiration. We find support for the traditional soil moisture-precipitation coupling in some dry or transitional regions where evapotranspiration is soil moisture limited. However, we also find that atmospheric feedbacks have a dampening effect on evapotranspiration in wet regions. The effect in wet regions is more widespread and more robust than the impact in dry regions which is consistent with first principles but surprisingly has not been quantified in prior work.  Unlike for water fluxes, land-atmosphere feedbacks do not consistently amplify or dampen photosynthesis changes, but remain important in regional hotspots. By adopting a more holistic definition of land-atmosphere coupling our analysis provides insights into where and how atmospheric feedbacks modulate terrestrial processes, posing a challenge to the widespread practice of developing and evaluating land models in an uncoupled configuration and then deploying them to understand and predict terrestrial processes in a coupled context.