The Endangered Species Act is arguably the country’s strongest law to prevent biodiversity loss. Enacted by Congress with overwhelming bi-partisan support, and signed into law in 1973 by former President Richard Nixon, the Act has helped recover the bald eagle, brown pelican and the American alligator, among others.

In its more than 40-year history, supporters credit the Act with preventing 99 percent of listed species from going extinct. As of June 2017, more than 2,200 animal and plants species are officially listed as threatened or endangered, with more waiting to be considered. Only 37 species have been recovered and delisted since 1978, of these, 19 occurred under former President Barack Obama. The Obama Administration has in fact delisted more species due to recovery than all previous administrations combined.

Critics point to this low delisting rate as proof the Act isn’t working. Since January 2017, Congress has introduced 28 bills seeking to undercut federal protections for certain species, weaken the Act through amendments or eliminate the Act entirely.

Even though less than 2 percent of listed species have yet to be recovered, the significance of the 37 species brought back from the brink of extinction should not be ignored. And with missteps and failures, more can be learned. Below are some notable endangered species wins and losses from the past year.

Current Status: Endangered

The Wyoming toad, the most endangered amphibian in North America, lives only in the Laramie River Valley of south-central Wyoming. Once plentiful in the region, the population crashed in the mid-1970s, most likely a result of insecticides, habitat loss and the amphibian chytrid fungus. The fist-sized toad was added to the endangered species list in January of 1984. From 1985 to 1987, the toad was feared extinct, until a small relict population was discovered. In 1989, biologists gathered the last of the remaining 10 wild toads to start captive breeding. Thousands of the resulting tadpoles – 160,000 to be exact – were released annually, but few made it to adulthood. By 2011, the recovery team surveyed only one toad.

In 2012 “Team Toad” changed tactics. Rather than release tadpoles directly into ponds, they used “reptaria”, wire release pens that kept the tadpoles, and later toadlets, safe from predators as they grew and acclimated to their new home. And the so-called “soft release” worked: Within a year, surveys detected toads that had survived to breeding age, not to mention egg clusters.

Back at the captive breeding facilities, scientists avoid inbreeding and maximize genetic diversity through carefully planned love connections carried out by a toad studbook keeper. In spring the toads are chilled to 38 degrees for just over a month. Simulating hibernation is thought to stimulate the release of hormones that trigger reproduction in the wild. Still, to get them in the mood, the arranged toad pairs receive supplemental hormones and are treated to the recorded breeding calls of fellow Wyoming toads.

While the species isn’t out of the woods yet, their wild population now numbers close to 1,500 toads. And where once a largely unknown species, the Wyoming toad now has a local microbrew named after it: Wyoming Toad Rye IPA.

Status: Proposed for delisting

The lesser long-nosed bat is one of only three nectar-feeding bats in the United States. With a tongue as long as its 3-inch body, the bat pollinates Saguaro cactus and other night-blooming desert succulents, including the blue agave from which tequila is produced. The species is one of the few long-distance migrants in the bat world. Not all of the bats migrate, but those that do head north each spring and summer, following a nectar trail of blooming plants more than 700 miles from Mexico to the Sonoran desert.

When initially listed in the U.S. in September of 1988, and Mexico six years later, the bat was struggling. Their numbers were thought to have dropped below 1,000 and with only 14 roosts. Habitat loss had been particularly damaging on both sides of the border. In Latin America and Mexico, many were mistakenly killed in their cave and mine roost sites in misguided attempts to eradicate vampire bats. Others were impacted as agave farmers shifted away from traditional practices.

To boost sugar content, agave farmers remove the plants’ flowers before they can be pollinated. Rodrigo Medellín – affectionately known as the “Bat Man of Mexico” – soon persuaded farmers to allow some if not all of their agave plants to flower, improving genetic diversity of the crops and providing protein- and sugar-rich fuels for the migrating bats. Medellin has even joined with a number of producers to begin marketing a certified “bat friendly” tequila.

In the U.S., a 10-year citizen science effort utilized southern Arizona residents to log night-time bat use at their hummingbird feeders. Their data helped biologists better understand lesser long-nosed bat migration patterns and provided opportunities to track bats back to their roost sites.

Today, the population now stands at 200,000 bats with 75 roosts. On January 6, 2017, the U.S. Fish and Wildlife Service proposed delisting the recovered bat.

Status: San Miguel, Santa Rosa and Santa Cruz island foxes delisted due to recovery; Santa Catalina island foxes threatened

The housecat-sized island fox has inhabited the Channel Islands off the coast of California for thousands of years. By 2000, the population was down to less than 100 individuals. Feral hogs had attracted golden eagles, which had moved in after the resident, fish-eating bald eagles were lost to DDT dumping off the coast. When not preying on piglets, the golden eagles turned to the foxes. And in 1999, canine distemper from introduced raccoons killed 95 percent of the foxes on Santa Catalina Island. When the four subspecies were listed in 2004, scientists gave the species a 50 percent chance of going extinct.

The complex recovery effort involved multiple moving parts: breeding island foxes in captivity, vaccinating both captive and wild foxes for canine distemper, relocating golden eagles to Northern California, culling the feral pigs – a move not without controversy – and reintroducing bald eagles.

In a comeback hailed as the fastest recovery of any mammal listed under the Endangered Species Act, the U.S. Fish & Wildlife Service delisted three of the four subspecies on Aug. 12, 2016. Today, their populations have surged to sustainable levels, ranging from 700 foxes on San Miguel Island to 2,100 foxes on Santa Cruz Island. The Santa Catalina Island subspecies was downlisted from endangered to threatened; it's continuing to recover, but at a slower pace.

Status: Extinct in the wild

Once common on Hawaii’s big island, the Hawaiian Crow, known locally as ʻalalā, is a foot-ball sized bird that is but one of two crow species shown to utilize tools. Following decades of devastating declines due to predation, disease and habitat loss, the species was listed as endangered in March of 1967; by 2002, it was extinct in the wild. Currently, only 130 ‘alala remain in the world, and all were born in captivity.

In late 2016, scientists released five juvenile male ʻalalā in the Pu‘u Maka‘ala Natural Area Reserve, an area of superb habitat where introduced predators like mongoose and rats had been eliminated, and feral cattle and goats fenced out. Within a week, three had died; two by ‘io, Hawaiian hawks, and one from starvation. The remaining two birds were captured and returned to the breeding facility.

In late summer or early fall of 2017, scientists will give the ʻalalā another shot, but with some tweaks to the release protocol. The Pu‘u Maka‘ala release site will be moved to a higher elevation in the hopes of keeping the ʻalalā out of ‘io’s preferred range, typically below 5,200 feet. They’ll also increase the availability of supplemental foods.

More birds, twelve in total including the two males who survived the first attempt, will be released. Two of these will be parent-raised as opposed to human-raised. And finally, the birds will be put through a rigorous predator aversion bootcamp where the ʻalalā will be taught to associate ‘io with a threat. Only the star graduates will participate in the release.

The authors of a 2015 paper in the Journal of Applied Ecology caution “conservation breeding and releases are not a panacea for conservation, but rather an arduous, difficult and unpredictable course to take when alternatives exist.” The ʻalalā team is well aware, but draws inspiration from the Hawaiian state bird, the the nēnē. In the 1940s, only 50 of the endangered geese remained on the islands. More than 60 years later, 2,700 captive-bred birds have been successfully released and the the population has rebounded.

Successes notwithstanding, nature is complex and unforgiving. And it's a lot easier to conserve species before they're on the brink of oblivion.