We have been depleting our water tables and putting garbage in our rivers, cutting down our forests and over-fishing our oceans, for a lot longer than the recent crisis in greenhouse gases that is bringing devastating run-away Climate Crisis.
If CO2 and Methane in the air could somehow be magically and cheaply pulled out of the air, a significant amount of devastation due to climate and weather would still have to be endured, but the present global warming catastrophe would rapidly start settling down.
On the other hand the oceans would still be under assault from escalating over-fishing that is becoming ever more devastating, the ocean acidity would still be a real threat to marine plankton (that is the basis of life in the ocean and of Oxygen planet-wide) and to coral reefs that provide so much marine diversity.
Plastics are not only causing well-known damage on the macro level (6-pack rings acting as nooses, and birds, fish and marine mammals with stomachs stuffed with plastic debris, etc. ...) but also offering totally unknown dangers as they break down to minute particles, suffusing their toxins to the very base of the food-chain, and every new plastic formulation offers new chances for unforeseen consequences.
New — and very persistent — chemicals are coming into our environment with minimal restraint and limited, often biased, testing. Then they react to each-other, the effects of sunlight, water, soil enzymes, animal digestion, leftover medication in the sewage, and so on … and we are rolling the dice each time to see if that undercuts some unseen biological process with huge results.
We need to not only tackle the global climate catastrophe, but also start treating the Earth with much more care on so many levels. Plus we are exhausting its bounty in so very many categories: from fresh water to bat dung, from salmon to sandalwood, from rich organic dirt to nice clean river sand … gorging on the inheritance of all our past relatives … and leaving less and less for those who would come after.
Another crucial issue is the need for infinite economic growth built into our system; there is no way to achieve that on a finite planet unless we discover zero-harm growth, and trying to maintain this cancerous growth before we drastically reduce the side-effects is going to kill us, one way or the other.
Most of these issues are partly technical in nature, but it is their effect on our present power and wealth-creation system which seem most intractable: people hanging on to influence even as the very basis for all our lives is selfishly put at risk.