From the air, the Chaco can look deceptively uniform -- an endless carpet of scrubby woodland stretching to the horizon under a bleached sky. On the ground, the impression dissolves. Altitude ranges from 100 to 839 meters above sea level, and rainfall varies dramatically from 1,400 millimeters in the wetter north to just 400 in the parched south. The Parapeti River threads through the landscape, feeding wetlands known as the Bañados de Izozog before disappearing into sand. Dunes rise in the southeast, where guanacos -- relatives of the llama more commonly associated with Patagonia -- roam terrain that feels more like desert than forest. Together with neighboring Otuquis National Park and the Nembi Guasu conservation area, Kaa-Iya anchors a corridor of roughly 60,000 square kilometers of protected Gran Chaco forest.

Camera trap studies by the Wildlife Conservation Society have estimated more than 1,000 jaguars living within the park, making Kaa-Iya one of the most important refuges on the planet for these big cats. But the jaguar is only the headliner. Pumas, ocelots, and maned wolves share the territory with 350 species of vertebrates, including 301 bird species and 89 species of snakes. The Chacoan peccary, a pig-like animal once thought to be extinct and known to science only from fossils until its rediscovery in 1971, still roams here. Giant armadillos dig their burrows in the clay soil, harpy eagles patrol the canopy, and black howler monkeys announce the dawn. Among the plants, 880 species of vascular flora have been cataloged, from the iron-hard red quebracho tree to the purple guayacan and the floss silk tree with its swollen, spiny trunk.

More than twenty Guarani communities line the western edge of the park along the Bañados de Izozog, villages with names like Guarirenda, Huirapendi, and Isiporenda. Chiquitano communities occupy the northern reaches, and scattered through the remoter zones are groups of Ayoreode origin, including some who remain uncontacted -- nomadic bands whose way of life predates any European presence in the Americas. In the park's southeastern corner lie the ruins of San Ignacio de Zamucos, a Jesuit mission active from 1724 to 1745 and then abandoned to the forest. The indigenous presence here is not incidental to the park's conservation; it is foundational. Since 1995, the park has operated under a co-management agreement with the Capitania del Alto y Bajo Izozog, an Izoceno-Guarani authority, making it one of the first national parks in the Americas to be formally co-administered with an indigenous organization.

The threats to Kaa-Iya read like a catalog of pressures facing wild spaces across South America. Hydrocarbon exploration brings seismic prospecting to the Bañados and petroleum drilling near Ustarez. The Bolivia-Brazil gas pipeline cuts through the region. Agricultural frontiers push inward as cattle ranching expands, and the Parapeti River faces diversion for irrigation. Illegal commercial hunting takes an unmeasured toll. Access to the park remains difficult -- roads become impassable in the rainy season, and many areas are reachable only by cattle paths or bridleways -- and that remoteness is both the park's vulnerability and its protection. With so few visitors, there are few witnesses to what is lost. But the Izoceno-Guarani communities, who have lived here for centuries and whose name for the place invokes ownership in the deepest sense, remain its most committed defenders.