In reply to mac_climb:
Which is not necessarily a good thing. Some plants will only grow in poor soil. Also, food residue can encourage non-native (ie not usually found in the place where you're dropping your litter) animals to move in, upsetting the balance for the life that was there already. Fruit peel is unsightly. There's no excuse for leaving anything, though I will confess to burying my Number 2's.
<rant> You often come across accounts of litter being dropped/found in mountaineering. The excuse seems to be, it was a really hard route mate, we had to do it. IMHO climbs/routes should be graded for a litter-free ascent and descent, and using public transport to get there from your house. Otherwise it doesn't count
</rant>