Newly-built Passageways Help Wildlife Safely Cross Roads

Here are the morning’s top stories on Friday, May 9, 2025…

• Roads are designed to connect people, but they often isolate wildlife. That’s why Caltrans, the National Park Service, and other government and non-government agencies seek to change the age-old definition of what roads are for: serving not just humans, but every living thing trying to get from place to place.
• The slow sinking of the nation’s biggest metropolitan areas — including parts of San Francisco — poses a growing hazard with vast socioeconomic consequences, researchers said in a new study.

Animal Crossing: Wildlife Use Secret Passageways to Safely Cut Through Roads

Los Angeles County’s Annenberg Wildlife Crossing is a 90-million-dollar bridge that is now under construction. It’s designed to connect green spaces between a freeway so animals can cross safely. But animals don’t need these kinds of crossings to be so expensive and fancy. There are smaller and cheaper ways to cross the road. 

For example, under five bridges along Highway 118, there are some additions to structures that were originally built in the early half of the 20th century. They’re simple ramps and fences created to be used by wildlife. These particular modifications represent an effort by Caltrans, the National Park Service, and other government and non-government agencies to protect wildlife and help them safely cross roads.

The state has really only prioritized linking habitats for the last 20 or 30 years. It was 2022 before California finally passed a law requiring Caltrans to include wildlife connectivity in its planning.

“We completely dissected the landscape across Southern California, and really across most of the U.S.,” says Justin Brown, a biologist for the National Parks Service who conducted road surveys along Highway 118 — counting roadkill and using trail cameras to see how animals were crossing the road.

Brown conducted another survey after the crossings were built, and found that not only were animals using the ramps, they were also getting killed less often on the roads — by something like 75%. And these secret crossings only cost $350,000.

Caltrans is planning seven more crossings just in this area, and dozens more statewide. The goal is to reconnect the green spaces severed by roads — a series of secret animal highways stretching from the Santa Monica mountains all the way up to Los Padres National Forest.

New Study Finds That Some Major Cities Across the Country Are Slowly Sinking

Some of the country’s cities, including parts of San Francisco, are slowly sinking. Because the impacted areas are usually in the densest parts of cities, as many as 34 million people could be affected and 29,000 buildings could be at high risk of damage, according to the study published this week in the journal Nature Cities.

For many cities, groundwater pumping is the culprit for the sinking. But in San Francisco, groundwater pumping isn’t a problem. Because much of the city’s fringes are built on filled-in land and the region is influenced by tectonic activity, the study’s authors suggest that soil is compacting over time in areas like Treasure Island and Islais Creek.

The authors also found that parts of the city subsided around 5 millimeters a year. On average, San Francisco sank a millimeter annually, Los Angeles 0.7 millimeters per year and San Diego 1.1 millimeters per year. Houston led all major U.S. cities, with about 20 millimeters of sinking annually. In some cities, including parts of San José, however, land is lifting slightly, potentially because of groundwater recharge.

Leonard Ohenhen, the lead author and a postdoctoral researcher at the Columbia Climate School’s Lamont-Doherty Earth Observatory, said the subsidence won’t be felt right away.

“The sky is not falling,” Ohenhen said. “This does not mean that you have to leave your homes right now. But in places like San Francisco, where you have tectonic forces and earthquakes, you’re already weakening the foundations of the buildings.”

While millimeters’ worth of land movement may seem tiny, subsidence can stress infrastructure over time, making it unsafe in the decades to come. But the good news is that with this knowledge, cities can prepare for a future that involves sinking land.