Efficient Charity: Do Unto Others...
What a provoking article - excellent! It's healthy for us to be asking these questions.
But I wonder about the dualistic nature of the questions posed in your 'how to guide'. Sometimes, in fact often, it is not a simple choice between two. Biodiversity, like culture, is much more complex than a graph can depict. The multiple layers move at different rhythms & speed and are instructed by differing motivations such as hormone, instinct, sex, survival, power, empathy (to name only a few).
My point is that systemic change is not a matter of choosing between the best charity - that approach only has one outcome which is how many lives to save in one monetary act - if we look at the world in a connected web than demonstrating empathy & care by looking after one's place (cleaning up the local beach) or protecting a rainforest for the future health of the planet - these are all responsibilities with different impacts that contribute to a greater whole. Helping a rainforest now may save millions of lives in the future compared to 10 lives treated for malaria now. And this is not just about humans! I don't think you can measure what you are trying to measure - it denies the complexity of life and reduces it to an economic plan.
Yes you can look at a 'how to guide' if you want to find the best charity and you do make great examples of how to make that decision - but sustaining life and survival is much deeper, chaotic and unknown.