It's the former; most energy is returned to space. Not that much energy is stored in biological systems on the macro scale -- heat waves cause wildfire, not th

It's the former; most energy is returned to space. Not that much energy is stored in biological systems on the macro scale -- heat waves cause wildfire, not the reverse. Besides, to keep homeostasis or anything resembling it, energy in needs to roughly equal energy out. Also vegetation is pretty terrible with absorbed energy efficiency. I mean, for goodness sake's it's green, the color right in the peak of the Sun's spectrum. That means the best wavelengths are all reflected. This is a feature, as it really helps quite a bit with keeping albedo higher, even in dark forests, for the purposes of preventing runaway global warming.