[AlDante2]

The big advantage trees have ove most man-made shade is that heat can convect through them. If you’ve ever sat underneath an umbrella at a café versus a beer garden under trees you’ll notice the difference. The umbrella shades, but traps reflected heat, re-radiating it below.

[agsnu]

Trees also provide a significant cooling effect by releasing water vapour into the air from the soil (evapotranspiration), which you won't get under an umbrella.