Nationalizing Nature tells the tale of Argentina's Iguazú National Park and Brazil's Iguaçu National Park, each named after Iguazu Falls, a massive cataract eighty meters high and 2.7 km wide. These mass tourist attractions began as destinations for moneyed elites. Each abuts an international border where Argentina, Brazil and Paraguay meet; each is in turn encircled by internal boundaries, dividing public from private space. Freitas contends that the parks – rhetorically construed as pristine natural spaces – are in fact products of human spatial practices and geopolitical forces.

In each park's history, contradictory goals – conservation, development and national security – alternately prevailed. From the 1930s, military and political goals prevailed. For the military, colonization by settlers helped secure borders against foreign incursions. For politicians, tourism infrastructure promoted economic development. The late 1960s witnessed a paradigm shift. Scientifically trained bureaucrats, influenced by international environmental–conservation norms, began to prevail. Settlers – previously encouraged to colonize the parks – were evicted by the Argentine and Brazilian military dictatorships.

Although primarily an environmental history, the book will resonate with historians of science: natural spaces – conceived as terra nullius – in fact result from human spatial practices. These range from environmental legislation and surveilling park borders to poaching jaguars and illegally harvesting heart-of-palm, a delicacy found in juçara palm trees. Freitas describes grilagem, private appropriation of public land with forged property titles, a widespread practice in Brazil, leading to vast swathes of Iguaçu forest being cleared by settlers, many of whom later resisted resettlement. The military sometimes treated resisters as subversives. Freitas emphasizes tensions between local actors and nation–states. Although the state sometimes prevailed, local actors – such as armed henchmen guarding illegal logging operations – could prove more powerful.

Historians of science will also recognize the emphasis on local actors. In 1899 Argentine naturalist Carlos Burmeister found a sign in the area inscribed ‘National Park, March 1897’. It was aspirational: no park existed. The sign had been posted by a Brazilian army captain stationed at a nearby outpost. A Brazilian, André Rebouças, first proposed a national park in 1876, four years after Yellowstone National Park's founding. He had visited Niagara Falls – another monumental, border-straddling cataract – and admired Yellowstone without having been there. To Rebouças, an engineer and an abolitionist, national parks represented progress and civilization. Similarly, in the first designs for the Argentine park, Charles Thays, a French-born architect living in Buenos Aires, proposed a rational, Cartesian park in the Parisian style.

By describing the transit of the practical expertise of creating parks to protect natural spaces, Freitas engages in discussions of circulation of scientific knowledge. In Argentina, many scientists responsible for national parks were European-born and -trained. The emphasis on North American and European influences may seemingly support dominant narratives of the circulation of knowledge, according to which scientific knowledge disseminates from the West to the Global South. But, Freitas emphasizes, neither Iguazú or Iguaçu subscribed to the exclusionary model of Yellowstone – neither park initially prohibited settlement or poaching.

If extensive knowledge flowed between Argentine and Brazilian scientist–bureaucrats and their international colleagues, comparatively little flowed between Argentina and Brazil. In 1984, when Iguazú became a UNESCO world heritage site, Brazil bristled at the suggestion that Iguaçu be lumped together with its Argentine counterpart. In 1986, Iguaçu became a separate world heritage site. Despite being rhetorically construed as pristine nature, the parks were imbued with national symbolism. Brazil gazetted Iguaçu in 1939, partly in response to Argentina's gazetting of Iguazú in 1934. Argentina's park was initially larger, but Brazil expanded its park to nearly four times the size of Argentina's, to reflect ‘Brazil's territorial greatness’ (p. 91).

Freitas's use of ‘nationalize’ refers both to colonization of borderlands with Argentine or Brazilian nationals, and to appropriation of private land by nation states. Brazil nationalized the Iguaçu border as part of President Getúlio Vargas's March to the West campaign. Vargas promoted a Manifest Destiny-like mission to conquer the hinterland. In Argentina's case, both its flagship national parks – including Nahuel Huapí, bordering Chile – encompassed disputed borderlands. The military encouraged settlement to secure the border. Argentina's national-park legislation stipulated that settlers be Argentine-born. Brazilian officials, in turn, fretted that the main languages spoken at the border were Spanish and Guaraní. They referred to Guaraní-speaking workers as ‘Paraguayans’, although many were likely Brazilian or Argentine. The exclusion of Guaraní-speaking workers from Brazil's or Argentina's definitions of the ideal settler suggests – though Freitas does not make this argument – that border nationalization efforts had racial overtones. Mara Dicenta, discussing Tierra del Fuego, argues that the introduction of Canadian beavers followed a Darwinian logic and reflected a desire to ‘whiten’ the natural environment. Freitas describes Argentina stocking Nahuel Huapí, in the snowy south, with Canadian moose and European deer. Even the animals may have contributed to the racially charged nationalization of borderlands.

Canadian moose and European deer share a provenance in the loci of modernity. A recurring motif in Latin American thought is the association of modernity – equated with economic development and scientific progress – with Europe and North America. The equation between modernity and the Global North and the argument that national parks are manifestations of modernity originate with the historical actors. But environmental science challenges associations between modernity and development. The tension between environmental conservation and economic development, which recurs throughout the book, reflects these differing definitions of modernity.

The flipside of equating modernity with Europe is equating barbarism with non-Europeans. Freitas's account of non-Europeans is tantalizing, but not as detailed as his account of other groups. Debt-bonded indigenous and mixed-race peoples – many of them Guaraní speakers – provided most of the labour to build the parks’ infrastructure, and for logging operations. However, the Brazilian government sought to delegitimize Guaraní speakers by denying their indigenous heritage. Freitas cites a Guaraní elder, Almeida, who reports that some Guaraní people once lived in what would become Iguaçu National Park. According to Almeida, the Guaraní were forcibly expelled, or their bodies thrown into the falls. Freitas adds that no written record exists. However, using aerial photographs, he identifies several sites that could be investigated by archaeologists for traces of the Guaraní.

The final chapter analyses aerial photographs of the Iguaçu Forest, and the real protagonist comes to the fore. As Freitas observes, assuming that the great national parks of the era were created to protect biodiversity is anachronistic; the notion emerged only in the 1980s. Rather, these parks were established to protect natural monuments. But although both Iguazú and Iguaçu are named after a monument – the eponymous waterfall – they mostly contain two kinds of subtropical forest: Upper Paraná Atlantic forest and Araucaria moist forest. These forests, and the biodiversity they support, are the current focus of the scientist–bureaucrats administering the parks. Much has been written about Amazonian deforestation. Between August 2003 and August 2004, a Belgium-sized area was cleared. Freitas extends this analysis to the Iguaçu subtropical forest, which is also being cleared at an alarming rate.

Historians of science are increasing interested in the history of the Global South. Freitas's book matters, not only because it describes the circulation of knowledge in a way that is inclusive of the Global South, but also because it shows how the conduct of science in the Global South affects the planet.