The Tijuana Estuary Visitor Center sits on the northern edge of a sweeping flat valley. The land is wedged between suburban housing tracts, the international border, the ocean and a military base.
Helicopters rumble overhead as inexperienced pilots train. That military mission is one reason this area is protected from development.
This is one of the few coastal wetlands to survive in California.
"As wetlands have been developed, through California and the world, we've lost a lot of the potential for those wetlands to function ecologically, not only for the species that live in those wetlands, but for us as well," said Brian Collins, refuge manager at the Tijuana River National Estuarine Research Reserve.
Collins sees a dynamic, living ecological system that has positive, real-world impacts on surrounding environments.
"If you like clean water at your beaches, you really want estuaries to clean that water as it comes down the watersheds," Collins said. "In many ways this system, this valley is a microcosm of the world's environmental problems and challenges and solutions."
This salt marsh habitat is considered a coastal wetland even though parts of it dry out during the year.
There are long sandy strips of land. Cactus are as common here as mud flats.
The variety is a sign that things are constantly in flux. What was once a mud flat might now be something else. He pointed to a damp spit of land.
"This system has changed. It succeeded into vegetative salt marsh. Today, it's a great rail habitat," Collins said.
Ridgeway rails are endangered birds that have long legs and beaks. That allows them to thrive in the tall grass that grows on the edge of mud flats. The creatures are among more than 300 species of birds that find their way to the estuary.
And while change is a part of the ecosystem, dramatic change could be devastating.
"We've thought a lot about how climate change, particularly sea level rise, is going to affect our coastal wetlands," said Jeff Crooks, research coordinator at the Tijuana River National Estuarine Research Reserve.
The salt marsh is a lot like a large lung, breathing in then exhaling ocean water. Crooks said the system has to be constantly measured to be understood and it has been measured.
"Basically what we say is we're taking the pulse of the estuary," Crooks said. "We're taking the vital signs. You just go out and measure day after day."
Those daily checks have created reams of data. Researchers track everything from water temperature, to acidification, and even the salt content of the water.
"Salinity, the amount of salt in the water, is basically the primary determinant of the plants and animals that live in this system. The types of things that you'll see here," Crooks said.
Saltier water might completely change what can grow in the estuary. Crooks is scouring those research logs to see what the immediate past says about the future.
The San Diego Foundation is funding the research into the estuary because of what it may reveal about climate change.
"We know that our coastal wetlands play a vital role in buffering the impact of storms, and filtering pollutants and providing outdoor recreation, nurseries for fisheries. So its really important to understand how these areas are changing," said Emily Young, vice president of community impact at the San Diego Foundation.
It is especially valuable for researchers to understand how quickly the change is happening or how dramatic that change ends up being.
Researchers said understanding climate change here has implications for the rest of the region.
