Mallory, Carlton, and Joe cross Pleasant Hill Road, stopping and starting like squirrels, dodging cars, exhaling deeply when they finally make the other side. A drone films overhead. They’ve done this routine many times — crossing roads, highways, and Interstates — all to illustrate the real danger wildlife faces. One of the leading causes of death for the endangered Florida panther is collision with vehicles. In 2014, 25 panthers were killed while crossing the road (their total population is estimated to be around 200 adults). For wildlife in the Everglades Headwaters near and around Lake Russell trying to head north toward the land along Reedy Creek and beyond (e.g. the Green Swamp), the only choice is to roll the dice and cross the chaos of Pleasant Hill Road. The smell of the swamp’s security comes from four lanes and a median away.

Danny, Phil, and I follow, making the shoulder and sliding down the steep hill to enter the swamp. In the enclosed swamp the sun’s heat bakes like an oven. The swamp floor is littered with browning water-lettuce pods and empty shells, mostly from invasive, non-native apple snails. Soon after entering the swamp, we come across a family of pileated woodpeckers playing . The large-bodied birds dart up and down a tree. Their red tufts of hair draw the eye like a neon sign in the swamp.

We trek a meandering course, constantly adjusting for downed trees and impenetrable thickets. The heat today is strong, I’m covered in sweat in minutes. Yesterday we didn’t hear the road until we came upon it, today we can’t escape its sounds.

An hour into the hike we hear the faint sound of a human voice. We all stop for a second, wondering if someone else is in the swamp. We keep walking until Danny says, “That’s from Home Depot or Lowes. I heard OUTSIDE LAWN & GARDEN.” Carlton checks the GPS on his phone; there’s a Lowes just east of us. In the middle of dense swamp, Reedy Creek to our left, we can hear a loudspeaker from Lowes. The wild-urban interface is razor-thin here. In addition to the geographic pressures of urbanization, wildlife must deal, too, with the growing encroachment of sound.

We move closer to Reedy Creek and notice the whole creek is covered in water hyacinth — some in bloom. There is not a speck of water uncovered by hyacinth; it would have been hell trying to paddle through this section of the creek. About 15 yards up the creek a giant gator, still as a log, sits sunning on the bank while two snowy egrets and a single great blue heron perch on limbs, watching the water.

We continue our slow march through the swamp, winding around thick areas and pausing occasionally for a drink or to check our coordinates. Around 2:30 p.m., we stop and Carlton notes we’re at the narrowest stretch of wild area — the smallest bottleneck — along the entire route.

Where we are, just north of the Pleasant Hill Road bridge overpass, the corridor is 450 meters wide, or about .28 miles. If one accounts for the edge effects (noise, light pollution, other disturbances) you lose about 60 to 100 meters of habitat on either side. Depending on what disturbances are present, there could be only 200 to 250 meters of interior forest conditions in which wildlife could move with the least amount of interruption.

Joe explains, “Animals in this area are never fully away from threats and noise. When it floods in summer, there may be no area to cross.”

“This isn’t what you want in a corridor,” Carlton adds. “So much potential for interaction with development. Think black bears and trash cans.”

Mallory points to a large drainage pipe left behind by a construction crew: “There has been some management work done to keep flow-ways open, especially around the bridge.” This isn’t just an issue for wildlife, either. Joe adds that the lack of natural land here means less area to absorb surface runoff, chemical fertilizer, and rainwater.

Humans neglect how swamps are important to their own lives. Swamps can support urban areas like nearby Tampa and Orlando. They store flood water, provide fresh air, absorb pollutants, and improve water clarity. A wild Florida is as essential to humans as it is to wildlife.