Environmentalism Under Capital
Many of the problems we face, in terms of the environment, even if they're not explicitly caused by capitalism, are made worse by capitalism and can't be solved while capitalism is the dominant economic structure we employ globally.
For example: almost any economic structure allows for manufacturing at some level, and they certainly allow for agriculture. These are major problems we have to face - how do we produce the things we need to live without overtaxing our environment? However, it's capitalism that's driven to produce in excess of need, or even want, because capitalism's development cycle is shark-like - it must always grow and never stop production, or the entire system collapses. That's how we've ended up with planned obsolescence and the concept of infinite growth.
I actually do think, in theory, that population growth is a problem - but the problem isn't really with "developing nations" (which is a Western, capitalist projection, anyhow) but with industrialized nations attempting to maintain population growth. (Which tends to taper off naturally, anyhow. We should let it.) But the reason it's a problem isn't an issue of living space, or even food production, but mostly, as I see it, water. And it's not drinking water that's the problem (it's a problem for people, but not a growth problem), but it's a problem with first-world industrial manufacturing turning people into faceless sales numbers.
We literally cannot solve environmental crises under the capitalist mode of production, because the capitalist mode of production cannot allow itself to cease - we simply have to find different things to purchase. And, I suppose in theory, we could simply attempt to circulate cash via media consumption, but by that stage, it's pointless because the very thing that makes it possible to circulate currency via media renders currency moot - the fact that media can be created and circulated indefinitely without loss. The physical issues of storage space (servers, electricity, and so on) are miniscule.
Not only is our current economic model unsustainable, but it's completely unnecessary. We wouldn't even have to change our lives that much - knocking the pillars out of planned obsolescence, rehabbing homes, re-distributing food, and ensuring clean water solves a lot of our problems right away. Entertainment is almost free. New technologies make food cheaper and easier to produce. Solving the transportation and infrastructure problems are paramount, but absolutely possible. We can actually see capitalism disintegrate before our eyes - it's the attempt to prop it up by force that will cause the colossal loss of life that is to come.