On the maths of not doing enough

I have been thinking about the maths of how much changing of the world I am responsible for taking on.  Obviously this makes little real sense but I am looking for some sort of workable starting point.  It makes an intuitive sense to me that we have more responsibility for those we are directly in relation with, and the closer the relation the more responsibility we have.  Peter Singer suggests that our ethical obligation to rescue a child drowning in front of us is identical to our ethical obligation to pay the same amount of money if it were to save the life of a child anywhere in the world, by funding a mosquito net for instance.  Yet Singer does find it difficult to find a limit to the obligations such a consequentialist view leads to.  Do you give all you have, always?  That is one magnificent answer of course.  It is in fact the only completely pure moral answer.  Short of that, does that leave us only with the demands made of us directly, and our responsibilities to those in our care?  40 billion chickens may be raised in battery farms, but we can still make sure our own chickens have company, shelter, the chance to roam, maybe the occasional strawberry muffin and a good rummage through a turned over compost heap.   8 million tons of plastic end up in the oceans every year but we will still pick up a plastic bag blowing past us on the street.  We do these things within a world collapsing around us and it isn’t enough.  What would be enough?  It isn’t enough, but we can at least do our share.  It is on this basis that Singer calculates the proportion of any one person’s income that should be given to help solve extreme poverty world-wide: taking the total amount it would cost to eliminate global poverty, and assigning graduated income-based donation percentages in order to cover that amount.  This works out as 2.5 % for instance of an income of $50,000, not impossible.  To combat climate change, the most effective solution is to plant trees.  One trillion trees could store 225 billion tons (205 billion metric tons) of carbon, or about two-thirds of the 330 billion tons (300 billion metric tons) of carbon that humans have released into the atmosphere since the Industrial Revolution began.  This is going to require an unprecedented coordination of will and resources from governments around the world and perhaps it makes little sense to work on an individual scale.  Yet if we divide 1 trillion by the number of people in the world, 7.7 billion, we get the number of trees, 130, that would be each individual’s share.  True, if everyone planted 130 trees in their own neighbourhood we’d soon run out of room for trees in the cities.  Even so, and even as I continue to vote for political parties and policies addressing poverty and climate change, not to mention kinder farming practices and the reduction of plastics, I am also going to plant 130 trees.