Explain why it is difficult to attach a value to the aesthetic qualities of biodiversity

Because aesthetics is subjective.  Everybody thinks beuty is worth a different amount of money.  Also, the beauty of nature has an unmeasurable effect on the human brain.  We need it to be healthy and relaxed and unstressed, but everyone's brain reacts differently.

i believe it would be the lungs.

metamorphism is the change of minerals or geologic texture (distinct arrangement of minerals) in pre-existing rocks (protoliths), without the protolith melting into liquid magma (a solid-state change). the change occurs primarily due to heat, pressure, and the introduction of chemically active fluids. i hoped i !