2 big environmental problems you probably don't know about — and 1 you should care more about.

It's not just global warming.

The Earth.

Photo by NASA.

It's probably fair to say that most of us enjoy the experience of living on it.

Unfortunately, all of us continuing to do so might take more work than previously thought. There are lots of forces conspiring to screw up the environment.

And not all of them get great press.

At the 2015 Aspen Ideas Festival, four experts were asked to name the "biggest environmental problem most people don't know about."

These were their answers:

1. How little water there is for all of us to drink.

Here in the U.S., we're pretty cavalier about our fresh water use.

How cavalier, you ask?

Pretty much sums it up. Photo by David Shankbone/Flickr.

But the abundance of clean water in the United States — and most of the Western world — obscures an important reality.

There really isn't all that much water on Earth to go around. And the more we pollute it, the bigger a disaster we're courting.

Because there's really no alternative.

Sadly "I'll just drink beer" is not a scalable solution. Photo by Nejmlez/Wikimedia Commons.

Oceanographer David Gallo explains it thusly:

The amount of fresh water on the Earth would fit into...

GIFs via The Atlantic/YouTube.

And over 7 billion people have a straw in the same grain of salt. Some speculate that competition for control of this limited supply between countries could eventually lead to famine, war, or worse. There's some evidence it's happening already.

Making sure we preserve clean drinking water for future generations, and figuring out how to distribute it to the people who need it most, are huge challenges that we've only just begun to address.

2. How acidic the oceans are becoming.

Earth's oceans, artist's rendering. Photo by Chris Metcalf/Flickr.

For the past 200 or so years, humanity has basically behaved like a drunk, entitled teenager with regard to the health of the planet, spewing trillions of tons of carbon dioxide into the atmosphere, consequences be damned. And the oceans have graciously taken on the role of our beleaguered parents, constantly bailing us out by absorbing much of that CO2, slowing down the process of global warming.

It's an unhealthy arrangement, but so far, it's worked.

Unfortunately, it's looking more and more like our sweet setup is unsustainable.

When the oceans absorb CO2, they become more acidic in a process known — creatively — as ocean acidification. And while minor changes in the pH of the ocean might not seem like a big deal to a bunch of hulking land apes, they are a huge deal if you're a tiny sea creature.

Higher ocean acidity makes it more difficult for shelled organisms like sea butterflies and oysters to calcify their shells. When these creatures die off, it trickles up the food chain — with potentially disastrous consequences for the larger creatures who eat them. Like fish. And whales. And, um. A certain primate species that loves its seafood. Not going to name names. Not going to say who.

Looking at you, Jeremy. Photo by torbakhopper/Flickr.

But you know who you are.

3. How hot the Earth is getting and how quickly.

Keep cool, dude. Photo by Ash Photoholic/Flickr.

Climate change. The big Kahuna. The whole banana. D-Day. Yahtzee.

And yes, I know. You're thinking, "Ugh. I know about this already." And maybe you do. But according to survey after survey after survey, too many of us don't. Not really, anyway. So the experts think, anyhow.

This year alone, unprecedented heat waves killed thousands in South Asia. Major changes in ocean currents are already afoot. Some scientists are predicting that sea levels could rise 10 times faster than previous thought by 2016.

A Pew Research Center poll from September 2014 found that action on climate change was near the bottom of most Americans' priorities lists. There's some evidence that people are finally starting to pay more attention, but even caring a lot might still not be enough. Because holy crap, it could be bad.

We need to take action, and we need to take it now. In so many ways, climate change isn't just an issue, it's the issue. Call up your senators and representatives and tell them to get it on the agenda. Spread the word! Get in the streets!

The Earth is pretty darn great. Let's make sure it doesn't go away.

But don't take it from me.

Take it from the experts.

Seriously. Listen. To. Them. These folks know what they're talking about: