Home to the deepest canyon in the Antilles and the highest waterfall in Puerto Rico, San Cristobal Canyon is touted as one of the 10 natural wonders of this tropical U.S. commonwealth.

These are impressive accolades, but it wasn't always this way. This gorgeous canyon spent 25 years as a smelly trash pit in the mid-20th century before being rescued and transformed into what is now one of Puerto Rico's most important ecological attractions.

Agricultural fields surround the canyon on all sides. (Photo: Catie Leary)

Due to the long history of agriculture on the island, only about 1 percent of the land in Puerto Rico is original forest, and a significant portion of that 1 percent is found within San Cristobal Canyon. These trees remained relatively untouched because while much of the surrounding land was cleared and developed for agricultural purposes (like nearby banana crops, pictured), the canyon's rugged, treacherous terrain has made it inaccessible and untenable for development.

That hasn't stopped humans from making their mark on the area, though. While farming the steep, rocky land was unfeasible, humans in the area found another use for it in the 1950s — namely, as a landfill for dumping all manners of waste and refuse.

"The canyon served as a landfill for five municipalities — Barranquitas, Aibonito, Orocovis, Naranjito, Comorio," explains María Cristina López, an environmental interpreter for Para La Naturaleza, the nonprofit educational arm of the Conservation Trust of Puerto Rico (CTPR). "They would come every day to dump trash — anything from construction materials to lightweight trash to clothing to car and truck parts. And not only did they dump the trash, they would also incinerate it."

It's taken years for the bottom of the canyon to recover from the decades of use as a trash dump site. (Photo: Puerto Rico Tourism Company)

By the 1960s, the local community had had enough, and a public campaign was started to stop the dumping and protect the area. One of the most pivotal figures in this fight was Don Félix Berríos, a local farmer who died in 2008 but during his life played a major role in galvanizing the community to protest the smell of the trash and the plummeting quality of the area's water, soil and air.

The community's hard work paid off in 1974, when the CTPR acquired a large chunk of the canyon and set forward a plan that would restore the natural wonder to its former glory and ensure it would stay protected for generations to come.

There's been a lot of progress in the 43 years since that initial acquisition. More lands surrounding the canyon have been donated to or bought by the trust over the past several decades, though according to López, about 40 percent of the canyon area remains unprotected as of 2016.

A map shows the patchwork of land — bought from farmers over the course of several decades — that currently makes up the protected areas of San Cristobal Canyon. (Photo: Catie Leary)

The map above shows how these efforts have come together slowly, adding more land to the protected tract while balancing the need for environmental conservation with the wishes of local communities. The progress comes bit by bit, but the trust has still managed to make big strides. One of the biggest victories was the discovery of biological indicators that show water quality has made a comeback and is now safe to swim in. While much of the progress is due to the clean-up efforts of hardworking volunteers, an estimated 90 percent of the recovery is the result of natural forces.

"Nature has done most of the cleaning through river floods and big rain events throughout the watershed," Lopez says, but she quickly adds that the work is far from over. "We still have people who don't know the value of protecting [nature] and not throwing trash into bodies of water."

Changing attitudes and welcoming visitors

Fault lines and rivers like the Rio Usabon are responsible for carving San Cristobal Canyon into what it is today. (Photo: Catie Leary)

Educating people and changing attitudes is the primary mission of Para La Naturaleza. Founded in 2013 with the goal of providing "transformative experiences that can inspire and motivate concrete actions for nature," Para La Naturaleza offers volunteer opportunities as well as guided adventure tours of the canyon.

Para La Naturaleza offers several different kinds of eco-tours that offer the chance to experience San Cristobal Canyon firsthand. Whether you're interested in an informative nature walk along the canyon's rim or you're hoping to abseil down some steep cliff walls and swim in the canyon's waters, there's a little something for every kind of nature buff.

In addition to Para La Naturaleza's tours, there are a number of local, family-owned tour companies that can also guide you safely into the canyon. While Para La Naturaleza's tours are some of the most affordable options ($85 per person for abseiling tours), they are only offered once a month and are conducted exclusively in Spanish. On the other hand, many of the other tour companies in the area tend to be a bit more expensive (typically around $150-200 per person for abseiling tours), but they run every day and are offered for English speakers.

Eco-tours like these demonstrate why working toward San Cristobal's comeback isn't just an environmental concern. As Puerto Rico positions itself as a force in the global eco-tourism industry, preserving the canyon and the many other natural attractions of the island becomes an economic concern.