Give an example of a system for water supply that has a positive feedback. We have discussed several in class today (such as reforestation leads to more water availability).
Describe why it is difficult to account for the benefits of some actions because of this positive feedback.
Why it is difficult:
Take the example of planting trees to restore and/or increase water availability in a watershed.
If you invest an amount in planting trees, what do you get to count for the benefit? Do you get to count the benefits accrued over just the short time only, or longer times?
What if the response is non-linear? Do you only get benefits if you planted enough trees to get over the threshold, or do you get to count the trees you planted as part of the sub-threshold number of trees needed?
ONLY 14 out of 32 gave a good answer.
Example answers and comments:
A water canal isn't a positive feedback system. The amount of water that goes in comes out. However the benefits may be many and varied.
Just because it would be difficult to account for the cause, doesn't address the question. It may be difficult to tell whether any environmental manipulation had a measurable impact. I was looking for cases in which the non-linearity leads to an expanding impact.
Several of you described the impact has having a "domino effect". I think that's a good way to describe the possible impact. Do you get to account for the first domino that falls or all of them?
One idea that was a healthier environment leads to hope in the community. That may be true and a good example of the expansion of impact. But, be careful not to rely on just saying that impacts like hope and hapiness can't be measured. That's not the point of the question.
The impacts may be unpredictable, because of the non-linear response. That makes it difficult to make the case that a particular manipulation lead to some improvement or degradation.