Some experts are concerned climate change will drive massive migrations as people are displaced from their homes, and it may already be happening. In a study published today in Science, researchers try to quantify how many people move from where to where under what conditions. They looked at asylum applications into the European Union and the weather in people's country of origin and found that as temperatures rose there, so did the number of people seeking asylum.

The context: It's timely — the U.S. Department of Defense has called climate change a "threat multiplier" and the defense authorization bill signed by President Trump last week acknowledges climate change as a "direct threat to the national security of the United States." Yet that view is noticeably absent from the president's National Security Strategy unveiled earlier this week.

What they found: At an average growing season temperature of about 68° Fahrenheit, which is the optimum one for agriculture, the number of applications for asylum was lowest. As the average temperature rose, so did the number of people from Somalia, Bangladesh and other warmer climate countries seeking asylum. But when cooler countries — such as Serbia — got warmer, fewer applications were received.

Read the full story here.

• Gene editing: Eileen O'Reilly on CRISPR being used to prevent an inherited form of deafness in mice.
• AI: A poker playing algorithm and other top stories in artificial intelligence from 2017, per Steve LeVine.
• Origins: In the search for the source of powerful gamma ray bursts in the universe, astronomers may have just found a first-of-its-kind structure, from yours truly.
• UFO? SETI's Seth Shostak on the Defense Department's program to investigate UFOs. He writes: "Remember: The CIA also spent millions of tax dollars examining the ESP phenomenon."

Erin Ross writes: In the beginning, Mars was a water world. But at some point in the planet's distant past, much of that water disappeared, leaving behind polar ice caps and a complex geology. Figuring out just where it went has been a major priority for scientists — life as we know it can't exist without water, and any future settlers would need a steady supply.

What's new: A new study, published Wednesday in Nature, suggests that much of what remains might be inaccessible. Some went into space, but even more of it may have sunk into the ground like a sponge, only to become bound up in minerals deep within the planet. "Mars, by virtue of its chemistry, was doomed from the start," study author Jon Wade, of Oxford University, tells Axios.

Read the full story here.

• Hazardous ice: Winter rain is freezing on top of the tundra making it difficult for reindeer to forage, suggesting "the benefits of warmer summers may soon be nullified by the countervailing consequences of warmer and wetter winters," per The Economist.
• A new GMO debate: Crops are increasingly being altered via gene editing techniques that, unlike with GMOs, don't involve inserting DNA from other organisms. The approach may redefine what is and isn't a genetically modified organism and raises questions about how to regulate this next generation of plants, per Antonio Regalado in MIT Technology Review.
• Doing the math: The New Yorker's D.T. Max profiles mathematician and hedge fund billionaire Jim Simons, whose new Flatiron Institute develops algorithms and computer models for "the scientific analysis of data" in astronomy, biology and climate science.

The earliest naturalists set out to document all of Earth's species. For five centuries, the plants of North and South America were plucked, dried and catalogued in the name of religion, medicine and science. Explorers and botanists amassed more than 22 million specimens that are housed in herbaria around the world. This includes the round-leaf cassia seen above that was collected in Brazil during Captain James Cook's first voyage to the New World in the 1760s.

Today researchers published a list of all known native vascular plants — the ferns, conifers and flowering plants we tend to notice — of the Americas. The stats:

• The Americas are home to nearly 125,000 species or 1/3 of the world's known vascular plants.
• There are 51,241 species in North America and 82,052 in South America.
• Only 8,300 species are shared between the continents and most plants are found in only one region.
• South America has 6% more plants than Africa but is only half its size. The edge: the diverse environments of the Andes and the Amazon.
• The authors predict there will be about 150,000 species documented in total by 2050.

The hope is that conservationists will use the database to manage a country's or region's plant assets, says Missouri Botanical Garden's Carmen Ulloa, who led the effort across multiple herbaria. "Now we know what we can conserve."