The numbers don’t lie: Humans are ruining this planet. Atmospheric carbon levels and ocean temperatures are going up. Arctic sea ice and biodiversity levels are going down—and no, the skyrocketing number of chickens doesn’t count toward biodiversity.
To comprehend and tackle those problems, scientists and policymakers need data—precise figures that show how Homo sapiens has transformed nearly the entire Earth in one way or another. To that end, a team of researchers has launched the Human Impacts Database, or HuID, a collection of over 300 (so far) critical figures, from sea level rise to the number of calories we as species get from animal products.
“Getting the numbers straight is the first step in trying to understand these systems, and we can learn a lot just by looking at the numbers,” says Rachel Banks, a biophysicist at Caltech and the Chan-Zuckerberg BioHub, and one of the lead authors of a paper describing HuID that publishes today in the journal Patterns. “And for sure, we want to keep these numbers updated and keep growing the database, but we also want to try to understand the Earth systems better.”
It’s worth your time to head over to the database and poke around. Banks and her colleagues combed through all kinds of information sources, from scientific papers to government reports, to find figures that run the gamut from measuring atmospheric processes to energy usage to mining. But if you spend enough time with HuID, you’ll find patterns. Earth’s systems are, after all, intimately linked with one another. “It seemed to us that a couple of key narratives emerged, and in a way they linked the story,” says study coauthor Rob Phillips, a physicist with Caltech and the Chan-Zuckerberg BioHub. “One of them is: What do we eat? And another one is: Where do we get our water? And then the last one is about power. If you follow those three threads, it’s a huge, huge part of the story.”
I got lost for hours in HuID. I’ve plucked out 14 particularly powerful, important, or just plain fascinating indicators—along with the graphs from the report that show their growth over time—that I think help illuminate those three threads.
First and Foremost: Global Warming
Thanks to humans loading the atmosphere with excess carbon, global surface temperatures have been rising steadily since 1850, as shown in the graph above. They’re now about 1.1 degrees Celsius warmer than in preindustrial times. That’s creeping up on the Paris Agreement’s optimistic goal of keeping that temperature below 1.5 degrees C, and an absolute threshold of 2 degrees. But it’s important to note that we’re talking global averages—so some places are warming much quicker than others. The Arctic, for example, is warming 4.5 times faster than the global average, because as it loses more sea ice, the darker underlying waters absorb more of the sun’s energy.
Rising Sea Levels, From Two Angles
As temperatures rise, glacial melt accelerates, driving up sea levels (shown in the graph above, in terms of millimeters above average sea level since 1900.)
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But that’s not the whole story. In the graph above, we see the contribution of a phenomenon called thermal expansion, also shown in millimeters of rise over the average since 1900. As the seas get warmer, they physically expand—and dramatically so. Thermal expansion is responsible for a third of sea level rise on its own.
Sea Change
Seas are getting warmer and also acidifying, due to the chemical reaction between excess atmospheric carbon and sea water. Humans are putting still more pressure on the oceans with overfishing. Global demand for fish has driven the rise of aquaculture, or the farming of fish. As the chart above shows, aquaculture now accounts for around half of fish harvests, up from 5 percent just 40 years ago.
Don’t Have a Cow, Man
The graph above does not represent the human population. It’s about cows. There are now 1.6 billion cattle on the planet that are used for beef and milk production. Their burps are a major source of methane, an extremely potent greenhouse gas. Cow stomachs act like fermentation vats, in which bacteria process hard-to-digest plant material and produce the gas as a byproduct. Plus cows need water and feed, which requires land to grow.
“Once you know how many cows are on the planet, that then leads you to ask: ‘Well, OK, how much food do you need to grow cattle?’” says Griffin Chure, a life scientist at Stanford University and Caltech, the other lead author of the paper. “And that tells you something about how much water you need for irrigation, and how much fertilizer. And if you’re talking about fertilizers, then how much nitrogen do we have to fix? And that gets you all the way to emissions. You pull a thread, and it all just kind of unravels.”
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Meating Up
As more people around the world ascend into the middle class, they can afford to eat more meat, as we can see in the graph above showing the global daily calorie supply from animal products (gleaned from both land and sea) per person. As the Intergovernmental Panel on Climate Change has warned, the global food system accounts for over a third of emissions, and producing all that chow also uses up vast swaths of land.
Water, Water, Not Everywhere
As the human population has swelled, we’re consuming more water, both for drinking and for irrigating crops. At the same time, climate change is making droughts more frequent and more intense, putting extreme pressure on water supplies. The graph above shows estimated global water use in cubic kilometers rising steadily since 1980, including for agriculture, power generation, and drinking.
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Power Play
Now for some good news for a change, shown in the two stunning graphs above. At top is power generated by wind and at bottom is solar, both shown in terawatts produced. The price of both technologies has cratered in recent years, meaning it’s now feasible to site wind turbines or solar panels in more places, even where they may not generate as much power as particularly sunny or windy areas.
City Slickers
Human populations are increasingly concentrating themselves in urban areas—more than half of humanity, in fact, as illustrated in the graph above. On the one hand, that’s an opportunity to explore more efficient ways of living. Scientists, for instance, are playing with the idea of growing crops on rooftops, shaded by solar panels. So in the future, city dwellers could grow their own food and generate their own electricity, with the added benefit of shading buildings, reducing the need for cooling.
Concrete Jungles
But there’s also a problem: Mass urbanization has driven the extraordinary growth of concrete production, shown in the graph above, in petagrams per year since 1910. (A petagram is 1015 grams.)
Producing all that concrete spews heaps of carbon, some 8 percent of global carbon emissions, though researchers are working on techniques to reduce that amount.
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Heat Advisory
All that concrete has an additional, hidden effect: Urban areas absorb the sun’s energy during the day and slowly release it at night, raising temperatures significantly higher than in surrounding rural areas. This is known as the urban heat island effect. As the world gets hotter, that’s helping drive demand for air conditioning units, as shown above in units installed since 1990. That in turn drives a gnarly feedback loop: AC units use a lot of energy, which drives up emissions, which leads to more warming.
Throwaway Living
Urbanization and income growth are also helping drive up plastic production, as companies saddle consumers with mountains of single-use plastic. Less than 10 percent of plastic is actually recycled. Instead, the stuff escapes en masse into the environment. Our clothes are also now made of plastic, so when you do laundry you flush millions of synthetic fibers out to sea. Microplastics are airborne, too, having thoroughly tainted the atmosphere. Scientists have looked at ocean sediments and found that microplastic concentrations have increased exponentially over the decades, mirroring the trend of plastic production you see in the graph above (measured in petagrams).
Stuffed
All told, the stuff humanity produces, known as anthropogenic mass, now outweighs all the organisms on this planet. As you can see in the graph above, with the mass measured in teratons (or trillions of tons), the production of stuff is increasing exponentially, with no signs of letting up.
Extracting the resources to produce anthropogenic mass is putting ever more pressure on the Earth’s organisms—civilization has grown like a biofilm around the planet, muscling out plants and animals. “What I am very personally interested in, going into the future, is trying to understand the degree of interconnectivity among all of these different human impacts,” says Chure. “What feedback loops may or may not exist? And ultimately, how the varied ways that humans are impacting the planet ultimately sculpt the biosphere as a whole.”