I read some of the answer and they were really interesting. I like to simplify so i will bring my modest simple answer and my advice : 

I have a amateur answer but i am not an expert although this topic interest me a lot being interested in sustainability, agronomy and ea (here global health and animal farming) : 

Firstly pro donating to animal farming : 

• if you believe in animal having a moral weight similar (1 - 10x) to humans it is probable that saving a human life might be negative compared to saving 100 - 1000 animals.  
• We know that our way of living is not sustainable. We also know that one reason why our lifestyle is not sustainable is animal farming. 

Secondly pro donating to save a life : 

• Saving a life is good (its one of the first moral reflex if it happens in front of you and)
• You never know what people will do with their life. They probably eat local non industrial products and dont cause much pollution if they are poor.

My opinion : Saving a human life will probably do a little bad because it causes the death of some animals (not necessarily factory farm) and causes pollutions - we are not sustainable (dependent of polluting fertilizer N,P,K). Saving animals will probably do a little good because we would be more sustainable. So I would focus on saving non-human animals because it will probably help all animals and the opposite is probably false.

Now my advice : 

• If you don't know the answer find some informations. When you have your answer keep being open-minded. I think this topic could be researched a hole lifetime without covering every aspect of it. Keep in mind since morals are subjectives there is no right answer. But since this quesion is important you should research the subject. I believe collective intelligence is the best "moral objectivity" we could acheive if everybody is well informed. 
• Life is never black or white and full of other dilemnas. Saving a human life or other animals are not your only two options wich brings me to my last opinion : before doing one or the other we should focus on discussing this subject with the most people possible. Or at least make sure everybody knows animals suffer (especially factory farmed) and everybody knows we can save lives with 5000$

I agree this is an important subject ! 

1. I think maybe because the most cost effective actions might be in rainforests where most of the biodiversity is (as i remember). This is more a political question of the countries near the equator. Most of them i dont know if there are a lot of people who know of ea in these countries (which is one of my main criticism about ea) but i believe there could be ea brasil. I would look in this direction :) 
2. Biodiversity is a complicated subject because numbers can't quite describe the       situation. I believe it is a systemical problem with systemical solutions like going vegetarian (proveg.org).

I saw a lot of comments of why it isnt a ea subject and i believe it good to compare advantages and disadvantages (i wont elaborate on your criticism).

Advantages : 

1. Many of humanity's vital ressources are linked to biodiversity. 
2. Many of the technologies that we discover come from biodiversity. Loss of biodiversity = loss of scientific information. 
3. Biodiversity is part of a systemic problem of the biocapicity of earth (see planetary boundaries) which is neglected.
4. Biodiversity and climate change make more probable existancial risk because they are systemic. This means for example war, famine and epidemics wich feed of each other and is in itself an underlooked and potentialy high impact.