♪ Man: The Navy's mission on San Clemente Island is to support Pacific Fleet training and exercises, and that includes joint exercises, as well, for the Navy, the Marine Corps, the Air Force, and the Army.

Man: About to make pack fire.

Martin: San Clemente Island provides a live fire range that is very unique to the Southern California area.

The inhabited portion of San Clemente Island is actually very small, and most of it is designated as protected areas, with small areas where target practice and training is conducted.

Booker: We need to train in Arctic environments, on coastlines.

We need to train in rivers, mountains.

We need to train in deserts, so we pick up all these unique habitats, and what we're managing is what's left over from public development.

Simonsen: Any biodiverse ecosystem is a series of interactions and linkages between multiple species at numerous trophic levels.

We don't want species to go extinct.

You know, we've seen historical photos of just really dense sheep populations, and as a result, just really the island was denuded.

I mean, sheep and goats are kind of known for grazing all the way down to the ground.

Narrator: Decades of pummeling by war exercises and overgrazing from invasive livestock have damaged the island and put its plants and animals on the endangered species list.

Island fox populations dropped to approximately 300 individuals at their lowest point.

By 1984, there were only 38 known Bell's sparrows on the island.

Between 1982 and 1998, as few as 14 shrikes could be counted.

The island larkspur could only be found in two small areas, and in 1990, only a single bushmallow was known to exist.

Simonsen: So the first one here is about probably 1980s, 1990s, when they were first starting the removal of the goats from the island.

It took nearly 20 years to remove all the goats, first starting with an estimate of almost 29,000 goats, and you can see, if you look along the coast all the way around this feature here, that everything was chewed down by the goats.

In this next photo, this is a picture of the eastern escarpment and really just shows how rugged the vegetation is.

You can see these really steep slopes and incised canyons, and in those incised canyons were basically refugia for a lot of the plant species that were either too steep or too rugged for the goats to get to.

Man: So we didn't have any noteworthy injuries?

Woman: Nope.

No noteworthy injuries.

Man: Injuries.

Woman: I didn't feel any ticks, either.

Gonzalez: No ticks?

Woman: I looked at the stomach, as well.

Man: Perfect.

That is everything we need here.

Gonzalez: OK. Ready for release?

Woman: Mm-hmm.

♪ Woman: The San Clemente loggerhead shrike is critically endangered.

In the early nineties, the San Diego Zoo and the Navy stepped in to intervene and help bolster the population again, which initially began with artificial incubation and hand-rearing efforts, but as, you know, time went on and we got enough individuals, we switched over to parental rearing, where we have the shrikes actually breeding and incubating their own eggs, raising their own chicks for release.

Narrator: The Navy and Fish and Wildlife Service removed invasive pig and goat populations by the mid nineties, allowing native species to repopulate.

With current conservation efforts, island fox populations have returned to stable numbers.

Bell's sparrow bounced back to more than 4,000 adults in 2023.

Bushmallow and larkspur can now be found across the island.

Booker: With any human use comes some level of influence in the natural environments.

Simonsen: You know, ideally for us to feel confident that the species has enough habitat that the populations are going to be sustainable into the future, we really want to see that there's populations, you know, dispersed across a broad area, that they have high population numbers, and those population trends are stable or increasing over time.

We also want to make sure that there's enough genetic variability in the population so that they have enough adaptive capacity to be able to respond to stochastic events or even potentially catastrophic events or be able to adapt to changes in their environment over time.

Booker: It slopes 2,000 feet into the Pacific Ocean, but it's covered in cactus and steep slopes.

Martin: The facilitation of the human aspect is actually the north side of the island near the airfield exclusively, and what that does is, it allows natural resources, wildlife, and vegetation that's native to this area to flourish in an area that would otherwise potentially be developed like much of Southern California.