From the air, the Amazon rainforest appears as an unbroken carpet of green stretching to every horizon. But within Mapinguari's boundaries, that carpet tears open to reveal something unexpected -- broad expanses of grassland and low shrub, pockets of savanna that scientists call campinas. These patches account for roughly nine percent of the park's area and exist in a delicate transition zone between two biomes. Some flood periodically during the wet season; during the dry months, they become susceptible to fire. Roughly 258,000 hectares of the savanna portion faces the threat of forest fires. The rest of the park is dense tropical forest -- 56 percent rainforest, 11 percent open submontane forest -- drained by at least nine rivers feeding into the Madeira and Purus systems. Average annual rainfall reaches 2,700 millimeters, and temperatures hover around 27 degrees Celsius year-round, with little variation between seasons.

In a world where biodiversity discoveries increasingly come from laboratory genetics rather than field observation, Mapinguari keeps delivering surprises the old-fashioned way. The Campina jay, Cyanocorax hafferi, was identified in the transitional habitat between the park's rainforest and its natural grasslands -- a bird that had evolved in these specific edge zones and gone unnoticed by science until recently. Stephen Nash's titi monkey, Callicebus stephennashi, also calls the park home, adding to a growing roster of primate species documented in the Purus-Madeira interfluvial region. The park's terrain is an extensive pediplain -- a gently eroded surface shaped by millennia of tropical weathering -- punctuated by river terraces, floodplains, and the ghost traces of ancient meanders. Altitudes begin at just 51 meters above sea level. It is low, flat, hot, wet, and alive in ways that science is still cataloging.

Mapinguari National Park was created by presidential decree on June 5, 2008, initially covering 1,572,422 hectares. The stated purpose was to preserve ecosystems of great ecological relevance and scenic beauty, particularly the savanna enclaves unique to this interfluvial region. The park is administered by ICMBio, the Chico Mendes Institute for Biodiversity Conservation, named for the rubber tapper and environmentalist murdered in 1988 for defending the Amazon. But the park's boundaries have been a moving target ever since its creation. In 2010, Law 12249 added roughly 180,900 hectares of former state conservation units -- the Rio Vermelho State Forests and parts of two ecological stations -- while simultaneously carving out the area that would be flooded by the Jirau Dam's reservoir. Two years later, Law 12,678 reduced the park's size again and opened the buffer zone to mining activities. The federal Attorney General challenged the 2010 boundary changes as unconstitutional in 2013, and the state legislature attempted to annul the state conservation units that had been absorbed, only to see those moves overturned in court.

Mapinguari does not exist in isolation. It is one node in a constellation of protected areas stretching across the BR-319 corridor, the controversial highway that links Manaus to Porto Velho. In 2012, federal authorities issued an ordinance requiring coordinated management plans for Mapinguari and its neighbors: the Abufari Biological Reserve, the Cunia Ecological Station, the Nascentes do Lago Jari National Park, three national forests, and four extractive reserves. The logic was simple -- piecemeal protection along a highway corridor guarantees piecemeal destruction. Together, these conservation units form a barrier against the deforestation front that has been advancing from the south along Rondonia's expanding agricultural frontier. Whether that barrier holds depends on enforcement, funding, and the political will to treat conservation and development as something other than a zero-sum game.