StingingSwingrays

My gut - as a marine biologist - is to say that nitrogen and phosphorous are more important to fix. We know the immediate & long term harms of N & P pollution, and we know that when it gets bad it can destroy an entire watershed (and all the livelihoods that depend on it, e.g. tourism, fisheries, etc.). We also know how to fix it, whereas we don’t yet know how to effectively remove microplastics already in the water column (or even if there’s a way to do it). Given this I’d say the priority is to focus on the problem that we 1) know how to solve 2) actually have the tools to solve it and 3) we know with confidence how harmful it will be if we don’t act.

You sort of answered the question to the actual problem there - population is a scapegoat for the bigger issue of consumption. That's reason that the first world, with its distinctly smaller population relative to the rest of the world, contributes the most per capita to worldwide waste.

Not OP, but speaking from experience - email, call, email, call any groups you are interested in working with - WWF, EPA, NOAA, NRDC, USGS, various museums, professors, and academic groups. Online applications almost never work. You're just one of hundreds of faceless names, almost all equally qualified, applying for the same position. By actually connecting with and chatting with someone, you become memorable. I'm now involved with Ocean Tracking Network by doing the above strategy. This applies to any job in any field.

Smaller related note, slash and burn techniques on a small scale can sometimes work really well (or even better than other techniques) to replenish soil nutrients and ultimately later increase biodiversity (intermediate disturbance hypothesis). It's huge clearcuts and massive monocropped fields that destroy ecosystems indefinitely.

Similar to another above response from Dr. Dyjack, but businesses are really, really good at cutting out waste from their production lines - less waste means more profits! This is at least one benefit for the environment. In terms of negative environment impacts of business, keep in mind that it is all driven by us, the consumer: the more we demand, the more they produce, meaning more pollution etc., even if they cut out waste from the actual production line.

Of course you are - so is literally every living being on this planet. So long as you eating and pooping within sustainable environmental constraints and within local environmental carrying capacities, there is no issue.