Discovering San Dieguito, one step and biome at a time

A round of cheers went up as two dozen 11th graders strode onto Del Mar’s dog beach, their classmates’ hearty applause punctuating a semester-long exploration of the San Dieguito River watershed, from the heights of Volcan Mountain to the brackish marshes that spill out into the Pacific.

For four months, almost 50 juniors from High Tech High North County, a charter school in San Marcos, amassed eye-opening lessons on the watershed’s biology and history. Biology teacher Matt Leader partnered with the San Dieguito River Valley Conservancy to devise a project that immersed the students in weekly research into the watershed’s five vegetative communities—or biomes—and the impacts wrought by their indigenous and then European inhabitants. The students split into two groups, two dozen each. One group readied to make five grueling hikes through each biome while the second group stayed back in the classroom, continuing their research, incorporating findings gathered on the hikes and preparing the art-meets-science exhibit in the Del Mar sands.

Starting with a Jan. 5 hike through coniferous forest atop Vulcan Mountain, the expedition ventured out to each biome, through Santa Ysabel, San Pasqual Valley and Lake Hodges before culminating with the 3-mile jaunt on Jan. 16 from the Del Mar Polo Fields to the sands of dog beach.

Strewn across the sand were mandalas each student made depicting one of the watershed’s native plants. A handful of the more dexterous students used the school’s laser cutter to carve from wood a detailed topographical map showing the watershed’s place within San Diego’s landscape. After six months of display at the school, the map will find a permanent home at the conservancy’s headquarters.

The expeditions were eye-opening in so many ways, students explained during the exhibit—from particulars of the California honeysuckle, which can alter its gender to fit its habitat, to the lasting legacy of the Battle of San Pasqual during the Mexican-American War, one of the most significant milestones in the development of the American West.

Human impacts were evident throughout, for example, Lake Hodges, where the century-old dam has choked off the supply of sand that would otherwise replenish Del Mar’s beach. Coniferous forests that once blanketed acre after acre throughout the watershed have been whittled down to isolated mountaintop clusters.

Kaitlyn Tremble learned an indelible lesson on the vulnerability of native plants to the havoc wrought by invasive species.

“People are like ‘Oh it’s just plants, why does it even matter?’ But there’s a reason,” she said. “We have so many endemic species here. I had no idea we were such a biodiversity hotspot. It’s pretty cool we’re such a unique area, so it’s really important to conserve it.”

For Katie Roner, even the bullet casings left behind by trap shooters —which leach lead into the water column and ravage the golden eagle —were a harsh reminder of how far-reaching those human impacts are.

“Everything effects everything,” she said. “Even if you don’t see it at first, it always comes back to us in the end—that idea that yes it’s a big picture but it’s also very specific to where we are.”

The project encapsulated exactly what the conservancy was hoping for as it steered the students toward the necessary data and guided the hikes, creating a view of the watershed few have opportunity to see.

“We want everybody to be able to experience our watershed, and this partnership has been a really great way to do that because these students come from such diverse backgrounds,” said Ana Lutz, the conservancy’s education manager. “Planting the seed of curiosity is way more powerful than handing someone a piece of information. Everyone who’s in this line of work can pinpoint that one moment in their life they fell in love with nature. We’re hoping to give that experience to these students so they can carry it throughout their whole life.”