This isnt speculation, we have a real world example in china. China is the "danger go back" sign we ignore as we speed towards the cliff.
China’s colossal industrial expansion of recent decades has depleted natural resources and polluted the skies and streams. China now consumes half the world’s coal supply. It leads all nations in emissions of carbon dioxide, the main contributor to global warming. Pollutants from its smokestacks cause acid rain in Seoul and Tokyo.
China’s experience shows how rising consumption and even modest rates of population growth magnify each other’s impact on the planet.
The country’s population of 1.3 billion is increasing, even with the controls on family size. What is driving the growth is that hundreds of millions of Chinese are still in their reproductive years. On such a huge base, even one or two children per couple adds large numbers — an effect known as population momentum.
The compounding forces of economic and population growth are a source of increasing concern to scientists. An international team of 1,300 researchers organized by the United Nations concluded that evidence points to “abrupt and potentially irreversible changes” in ecosystems in the next few decades, including mass extinctions and rapid climate change.
Within China, signs of environmental damage are pervasive: massive fish kills, lung-searing smog, denuded landscapes. They have stirred popular discontent and the beginnings of greater official concern for curbing pollution and preserving natural resources.
How this drama plays out is not merely China’s concern. Because of the nation’s sheer size, the rest of the world has an enormous stake in the outcome. [I can seldom see San Francisco’s Golden Gate bridge, 12 miles away, anymore because of coal power plant and other pollution blowing in from China that muddies Bay Area skies — aha, right after I wrote this, I continued reading the article, and it says “almost 25% of the pollutants in the air above Los Angeles originated in China, the Environmental Protection Agency has found.”].
Overpopulation is destroying the planet — China for example