Four years ago, we noted amid apparently worsening weather systems — more drought, wilder storms, bigger wildfires, etc. — that while it may seem as though Mother Earth has had enough of her dominant species and is striking back, in reality, we’re not significant enough to warrant such attention. Truth is, we’re pests, at most, on a planetary scale.

Sure, we can pollute the water. We can overfish areas. We can spew enough noxious gases to throw off the balance of the ecosystem’s heating/cooling. We can provoke drought, start fires, clear cut jungles and pave natural terrain. We could even, still, set off enough nuclear bombs to cover the planet in radiation.

And what we’d get for any or all of that is a world that’s barely — or not at all — inhabitable. We can kill off other species we rely upon for food, shelter and other necessities. We might extinguish needed resources or tilt weather patterns even further to the extreme.

In short, we may kill ourselves off. The Earth, on the other hand … this miraculous home with just the perfect conditions to support our form of life, will continue to spin merrily along. You see, it matters not to our host planet whether the parasites that inhabit it stay, leave or die off. It has no sense of purpose in maintaining our existence. The term “Mother Earth” — or “Mother Nature” — is itself a construct we created, perhaps to lessen the sense that our home world is somehow in this with us; that we’re not on our own.

It is true, however, that this has been a hospitable place to evolve. Miraculous, indeed. What are the odds of a random mass of rock and gas somehow collecting, along its journey, the exact elements, in proportion, to sustain carbon-based life; while falling into an orbit at just the right temperate zone? One in a million? A trillion? Something far larger?

Recent astronomical discoveries have made clear it’s certainly not unheard of. And we might have predicted this, given the vastness of space, the untold number of suns and planets, in play. Yet we’ve located a few that are pretty similar, just within our “vision” — that is, how far into the cosmos we can reach with our telescopes, reading radio waves and spectral signatures.

Keep in mind, though, that the nearest of those “habitable” planets, likely orbiting the star Proxima Centauri, would take 6,300 years to reach, at our current technological limits. If we could somehow develop speed-of-light travel, it would take only a little over four years.

Then there’s Mars. We’ve reached that with probes and robots. Just this past week we flew a tiny helicopter there. And there are clear signs of past water, rivers, polar caps, tiki bars. OK we made up at least one of those. But now, Mars is no more habitable than the moon, or any other chunk of rock that happens to be reachable. It would take an extraordinary effort of manpower and technology to “colonize” either. And that doesn’t even account for the politics involved.

All of this is to say, the likelihood of finding a replacement planet is extremely low. Not in our lifetime. Nor our children’s.

Given that, it seems a pretty good idea to take the best care of the one we’ve got, seeing as how it’s already suitable for us and all. So, about those Earth Day calls for action you may be hearing on this 52nd Earth Day, and the reasoning behind them.

Extended heat waves mean more deaths from heat stroke and dehydration, and increased cardiovascular, respiratory and cerebrovascular disease. This may be most felt in developing nations that lack air-conditioning and other modern amenities, but it will also hit hard in urban areas, where a lack of cooling trees and greenery is exacerbated by heat-absorbing asphalt.

A warmer planet also means less usable land for crops, and will require more water and energy to keep what crops we do have growing. Warmer temperatures will also increase the frequency of days with unhealthy levels of ground-level ozone and other particulates, leading to an increase in respiratory illness and deaths.

A larger tropical region means a larger population of mosquitoes, ticks and fleas, which carry viruses, bacteria and parasites. So expect a surge in West Nile, EEE, malaria and Lyme disease, among other potentially fatal conditions. Add in rising seas, droughts and the extinction of species we use for food, and we can easily imagine the competition for scarcer resources causing an uptick in war as well.

That’s a pretty damning future, but not one set in stone. We’ve seen, even in the past year, that cutting back on activities that add to greenhouse gases for a few weeks or months can have a significant effect. Imagine dedicating years to such a goal.

Even if the Earth will, figuratively, shrug off the damage we’re causing in a few millennia, the effects on mankind will be much more severe. In taking care of the planet we live on, we’re really taking care of ourselves.

So be selfish, and be green.