Global warming is important, but only one environmental problem, so important to consider here, but not the only environmental issue.
Contributing to every environmental issue, including this one, is overpopulation. Humans have altered every continent, reducing biodiversity, introducing species that don't handle local climates as well, or too well and displace existing ones, making extinct species, and so on. I'm no expert, but the situation in Australia looks related to huge cities and lots of farms supporting a much larger human population than had ever lived there reducing biodiversity and resilience to fire, exacerbated by global warming.
People fear discussing overpopulation because they only know of China's policy and eugenics, as did I until I learned of the successful, non-coercive policies of Thailand, Iran, Mexico, etc that increased peace, prosperity, and stability.
I first learned of successful noncoercive birthrate reducing policies through Alan Weisman's excellent Countdown https://www.amazon.com/Countdown-Last-Best-Future-Earth/dp/0..., and of the critical importance of population through Limits to Growth https://www.amazon.com/Limits-Growth-Donella-H-Meadows/dp/19....
Those examples show that we can peacefully and stably lower birth rate to increase peace and prosperity and ease all other environmental problems. Steady-state following de-growth works more successfully on a full finite planet than pushing economic and population growth forever, which exacerbates problems like these and increases their impact on humans and other wildlife.
> The scramble for sand is destroying the Mekong
> Overpopulation is destroying the Mekong
You might add "one way is the scramble for sand" though there are plenty others.
Learning about various nations' successful, noncoercive programs to lower birthrate that are as far from China's policy, forced abortions, or eugenics as day from night, and that increased prosperity and happiness, leads you to embrace such programs. The book Countdown by Alan Weiss https://www.amazon.com/Countdown-Last-Best-Future-Earth/dp/0... describes several such programs, including in Thailand, Iran, Costa Rica, Mexico, and others.
The most effective solution to the Mekong situation, however partial, is contraception and family planning education.