7 things we've learned about Earth since the last Earth Day

This year’s Earth Day, April 22, will be dominated by March for Science rallies taking place in Washington, DC, and dozens of other cities around the world.

But I also like to mark Earth Day by looking at some of the best new discoveries we've made about this breathing, seething, never-dull planet of ours — the only place in the universe where life is known to exist.

After all, a lot has changed since the very first Earth Day in 1970. Back then, America's most urgent environmental problems were smog and water pollution. In the years since, we've made remarkable progress mopping that up, only to confront fresh challenges like global warming and ocean acidification. Even today, our knowledge of the Earth keeps evolving with each passing year. We've uncovered new geological features. We've brought endangered species back from the brink of extinction. We've transformed the atmosphere, for better and worse.

So here's a list of some of the most surprising, hopeful, and worrisome things we've learned about Earth since the last Earth Day:

1) Scientists (sort of) discovered an entire new continent: Zealandia!

(Mortimer et al., 2017)

Okay, scientists didn’t discover New Zealand this year. It’s been sitting there for ages. But in February 2017, a team of researchers led by geologist Nick Mortimer published a paper arguing that we should take a second look at this corner of the world. Because New Zealand isn’t just a tiny island nation. It’s arguably part of a unique 1.9-million-square-mile continent, not too different from North America or South America.

Scientists have been collecting data on the slab of continental crust that surrounds New Zealand and New Caledonia for decades (much of which is underwater, of course). Over time, they’ve come to realize that this landmass has a distinctive geology and well-defined structure that separates it from the nearby continent of Australia. If you follow certain definitions of what constitutes a “continent,” Zealandia is its own thing.

This isn’t just a pedantic name change. The realization that Zealandia is actually an independent continent could help scientists better understand “the cohesion and breakup of continental crust," the authors write.

But don’t go ripping up your geography textbooks just yet. There’s no official definition of “continent,” and scientists will likely be debating this for years. (Much like there are still debates over whether Pluto is a “planet.”) But it’s a good reminder that scientific discoveries don’t always have to entail new, never-before-seen objects. Sometimes they entail looking at familiar objects with fresh eyes.

2) We've found dozens of new species — like this fluorescent frog...

(Nature)

At this point, scientists have described about 1.5 million different species on the Earth. That sounds like a lot, but estimates suggest there are at least another 4 million species waiting to be documented. And we’re finding hundreds every year.

One nifty discovery came in March, when researchers published a paper describing the South American polka dot tree frog, which gives off a green-blue glow when placed under ultraviolet light. The frog doesn’t glow it the dark, exactly; instead it absorbs light at short wavelengths and re-emits it at longer wavelengths. (Glow-in-the-dark creatures, like fireflies, are known as bioluminescent.) But only a few species can pull off this trick — and this is the first known fluorescent amphibian.

The past year has brought a wealth of other new species into view, too, from a cave-dwelling spider with red fangs in Mexico to a ghostly octopod nicknamed “Casper” on the ocean floor that, alas, may be under threat from deep-sea mining. Last September, a genetic analysis even revealed that there are four distinct species of giraffe, not just one, as previously thought.

3) But we’re also losing species at an alarming rate

Scott M. Denderson / April the Giraffe

Sadly, it can’t all be good news.

One of the reasons scientists are rushing to discover and describe as many species as they can is that we’re also losing a great deal of wildlife at a shocking rate. As human civilization expands, and cities, farms, and mines proliferate, natural habitats and wilderness keep shrinking, driving many species to the brink. Global warming is also expected to drastically transform the historical range of a great many plants, birds, and animals — and many species may prove unable to adapt.

Last June, scientists announced that the Bramble Cay melomys, a small rodent native to the Great Barrier Reef, has likely gone extinct as sea-level rise had inundated the small island it called home. If so, this could likely be the first known mammal to go extinct due to global warming (scientists have already blamed the changing climate for wiping out a few frog species).

Ecologists keep warning that many, many more extinctions could soon follow if we don’t act quickly to protect what wildlife remains. Giraffe populations have declined 40 percent in the last 30 years. More than half of all primate species are sliding down the path toward non-existence. One enormous challenge of the 21st century is making sure that Earth’s rich biodiversity doesn’t just end up a distant memory, seen only in museums and old photos. (Here are a few ideas for slowing further extinctions.)

4) The world’s oldest fossils may have been found in Canada — at least 3.7 billion years old

(Matthew Dowd/Flickr)

The history of human civilization can be condensed into less than 10,000 years, a blink of an eye in geological time. Earth, of course, has been around far, far longer than that, a timescale that’s often staggering to contemplate.

In March 2017, scientists with the University College of London announced they had unearthed layers of quartz in Canada containing “microfossils” of bacteria that once lived underwater near hydrothermal vents, feasting on chemical reactions involving iron for their energy. The kicker? These rocks were thought to have formed between 3.7 and 4.3 billion years ago — which would make these the oldest fossils ever found.

To put this in perspective, the Earth was thought to have formed about 4.54 billion years ago. The first oceans likely appeared about 4.41 billion years ago. Somehow, the earliest forms of life wriggled into existence not long after that. (By “not long,” of course, I’m talking hundreds of millions of years. No big deal.)

“Our discovery supports the idea that life emerged from hot, seafloor vents shortly after planet Earth formed,” lead author Matthew Dodd said when the results were announced. To be sure, measuring the exact dates of rocks this old is a tricky task, and scientists will likely debate their precise age for some time. Previously, the oldest known microfossils were thought to be embedded in 3.4-billion-year-old rocks found in Western Australia, though there’s dispute over whether those fossils were biological.

5) A new type of cloud was added to the official cloud atlas: Asperitas

(World Meteorological Organization)

The International Cloud Atlas has been used to train meteorologists since the late 19th century. And there haven’t been any new clouds added in decades — which makes intuitive sense, since you’d assume we already know everything there is to know about the sky above us.

But that all changed this year.

Ever since 2006, the delightfully named Cloud Appreciation Society, a group of British weather enthusiasts, has been photographing and documenting an unusual type of turbulent cloud that can’t be found anywhere in the atlas. After much prodding and formal debate, the World Meteorological Organization agreed that this was indeed a distinct formation and added this new cloud, dubbed the Asperitas, to its taxonomy.

“Asperitas,” the new edition of the atlas says, “is characterized by localized waves in the cloud base, either smooth or dappled with smaller features, sometimes descending into sharp points, as if viewing a roughened sea surface from below.” You can see more lovely pictures here.

The Cloud Appreciation Society, for its part, hailed the recognition of the Asperitas cloud as a triumph of citizen science, noting that the rise of smartphones has enabled non-scientists to document all sorts of phenomena in the world around us — and allow scientists to form a much richer picture of this planet of ours.

6) The Great Barrier Reef is in more trouble than we thought

The Ocean Agency/XL Catlin Seaview Survey/Richard Vevers

Coral reefs are often dubbed the rain forests of the ocean. They cover just 0.1 percent of the sea floor but are home to 25 percent of marine fish species. They sustain vital fishing industries, and they’re popular spots for divers and snorkelers.

Unfortunately, these reefs are also extremely vulnerable to rising ocean temperatures and global warming. When the waters get too hot, the living coral polyps that build the reef expel the zooxanthellae that live in their hard skeletons and provide them with nutrients. Once that happens, the coral start suffering and take on a ghastly white color — known as “bleaching.” During severe bleaching events, many coral can die, which in turn hurts all the marine life that depend on the reef.

Over the past year, Australia’s majestic Great Barrier Reef has been absolutely walloped by unusually warm ocean temperatures and has suffered back-to-back bleaching events — the first time that’s ever happened. Huge swathes of the reef are now dying. Worse, these bleaching events are expected to become increasingly common in the future if the planet keeps heating up, and the reef will struggle to recover. At a certain point, much of it will be gone for good.

Now, there are steps Australia can take to try to salvage its reef — or at least give it a fighting chance in the face of global warming. Humans can limit fertilizer and sewage runoff that further damage the coral. We can avoid overfishing key herbivores like the rabbitfish that nurture the reefs by clearing away excessive algae.

But ultimately, limiting climate change is the crucial step if we don’t want to see these ecosystems vanish forever. "At 2°C [of global warming]," Mark Eakin, who runs NOAA's Coral Reef Watch program, told me last year, "we are likely to lose numerous species of coral and well over half of the world's coral reefs."

7) But humans also showed that they can come together to tackle big environmental problems

Photo by VCG/VCG via Getty Images

I'm going to end this list on a more hopeful note. Humans have done a lot of damage to this planet and the other species on it, it’s true. But we’ve also shown a remarkable ability to save other species, to restore ecosystems, to blunt the harm we’ve caused.

Over the past year, we’ve brought the giant panda back from the brink of extinction, thanks to concerted conservation efforts. Scientists are developing a vaccine to protect the endangered Tasmanian devil from dying in the face of a lethal facial tumor disease. Just this spring, ecologists at the Smithsonian Institute announced that the scimitar-horned oryx, a sort of antelope once extinct in the wild, had been reintroduced in Chad and was now breeding again.

“Although some of these achievements may seem limited in scope,” wrote Andrew Balmford and Nancy Knowlton in a recent Science essay, “much of conservation depends on the accumulation of small-scale advances across the planet.”

Humans have banded together to do much bigger things too, the authors note. More than 5 percent of the world’s oceans are now Marine Protected Areas, up from 1 percent a decade ago. The nations of the world are making remarkable progress in bolstering clean energy and moving away from coal, a key driver of global warming. Yes, these efforts are still insufficient in the face of some of the massive environmental problems we’re facing. But it’s hardly all doom and gloom.

Just as humans are capable of making astounding discoveries about this planet, we’re capable of altering its trajectory. The idea behind the original Earth Day was that we can harness human ingenuity to alter that trajectory for the better. There are certainly signs of that, if you know where to look.

Further reading: 15 before-and-after images that show how we're transforming the planet

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