Tony Smith (in collaboration with Celulose Irani): Bat Cave, 1969/2013, 4,800 cardboard pieces; in "Portals, Forecasts and Monotypes" at the Bienal do Mercosul.

Perched on a cluster of sun-bleached rocks that barely protrudes from the Guaíba Lake—or river, depending on whom you ask—a former prison for political dissenters and other miscreants steadily erodes, turning from bastion of Brazil's Department of Political and Social Order into a modern-day ruin. The moldering walls are emblazoned with obscene, cryptic and mawkish graffiti; traces of persecution are overlaid by those of teenage assignations and drunken exploits. I debarked on Sept. 13, having been transported on a sluggish ferryboat with a dozen other sailors—curators, writers and artists—for the purpose of considering the island as a promiscuous metaphor: utopia and desolation, discovery and projection; Toussaint-Louverture and Odysseus, Columbus and Gauguin.

The occasion was "Weather Permitting," the ninth Bienal do Mercosul, which took place in the proximate city of Porto Alegre, a sprawling industrial port and the capital of the country's southernmost state. Between May and November, Porto Alegre was overtaken by exhibitions, performances, educational initiatives, publications and expeditions, all somehow devoted to the relationships between nature and culture, perception and communication, science and speculation. Among the dozens of remarkable artworks included in the main multi-venue exhibition, "Portals, Forecasts and Monotypes," were Tony Smith's Bat Cave (1969), a monumental cardboard sculptural environment originally created with Container Corporation of America and lately reconstructed with local paper company Celulose Irani; Elena Damiani's spectral landscapes printed on silk chiffon and bound in arrangements of freestanding black frames and stones (2013); and Nicholas Mangan's ingenious, emotive video installation Progress in Action (2012-13), which featured a silent film documenting a 1989 revolt against exploitative copper miners by Papua New Guineans relying on home-brewed coconut oil, and was itself situated within—and also powered by—the artist's own DIY copra-fuel refinery.

The prison island, Ilha das Pedras Brancas (White Stones Island), acted as a "gravitational force," in the words of Sofia Hernández Chong Cuy, who led the biennial's team of eight curators: a place of monthly pilgrimage and discussion, a totem fixed to the edge of the horizon. During the opening weekend, sound artist Tarek Atoui literalized this traffic between the island and the mainland. For Signal Jammed Geographies, Atoui stationed himself on the roof of the Usina do Gasómetro, a cavernous former power station that served as one of the biennial's four exhibition venues, and sculpted sounds transmitted from microphones installed on Ilha das Pedras Brancas, which was in turn receiving radio waves from atop the former power station. When Atoui began to play, the lake below was glassy and resplendent with sunshine, but soon he was beset by heavy gusts, and for the next 30 minutes the controlled feedback loop slipped between murky melodies and obstreperous noise.

The relationship between local weather and the activities of a biennial might seem superfluous, a matter of chance, but in Porto Alegre the vicissitudes of the environment were fundamental. The city's frequent and unpredictable rainstorms and temperature changes provided the backdrop for an investigation of the "atmospheric disturbances"—a term lifted by the curators from the title of Rivka Galchen's novel of meteorology and delusion—that trigger migration and innovation, political change and psychological distress. In the main exhibition, Aurélien Gamboni and Sandrine Teixido directly addressed weather-borne apocalypse in The Maelström Agency (2012), which reflected on the 1941 flood that washed away much of Porto Alegre, and united many of the biennial's concerns and strategies. The artists incorporated archival documents, interviews, diagrams, reading groups and their own fictionalized account of the flood. The Maelström Agency gestures toward a world in which the telluric cycles that have always given us meaning and stability no longer obtain, in which each rainstorm portends the inconceivable cataclysm of environmental collapse.

Of course, however inconceivable, that collapse is now imagined incessantly, whether in Hollywood blockbusters or United Nations assemblies. Such projections are a frequent subject of The Cloud, an anthology edited by the biennial's curators, with essays and stories by authors such as Jules Verne, Walter De Maria, Bruno Latour and Eduardo Viveiros de Castro. Villém Flusser writes incisively, often comically, about the meaning of the moon, which he describes as a television event, a folk tale, a newspaper story, as well as a scientific fact; ultimately, the moon is the "property of NASA," though we are still conditioned to behold it as "the Earth's natural satellite"—just as the Greeks persisted in seeing the moon as a goddess. "We live in two worlds," Flusser observes, "one that is given and the other that is provoked by the attention we pay to it."

This friction between knowledge made from nature and nature made from knowledge was addressed impressively in Imagination Machines, a series of commissioned projects that matched local companies and research institutes with artists such as Lucy Skaer, Cinthia Marcelle, Daniel Steegmann Mangrané and Luiz Roque. The resulting works were exhibited alongside paragons of the Art and Technology program of the Los Angeles County Museum of Art, which between 1967 and 1971 facilitated partnerships between artists and corporations. Chief among the Art and Technology projects was Robert Rauschenberg's tumultuous Mud Muse (1971), a large tank filled with drilling mud loudly effervescing in response to sounds captured by several microphones, which highlighted how contemporary works often put new technologies, many of them born from the military-industrial complex, in service of artistic experimentation. The artists in "Weather Permitting" tended to be more discreet, wary of the value added to art by such technological augmentation. Skaer's contribution was exemplary, and quietly revelatory. She also worked with Celulose Irani, which manufactures commercial resin from eucalyptus trees; she reshaped the standard 25-kilogram blocks into emerald-cut gemstones. While a number of the resin blocks were exhibited in Porto Alegre, they will eventually all be placed back into circulation as industrial products, at which point they may provoke a subtle shift in the relationship between the various parties involved in the transformation of trees into varnishes, adhesives, glazing agents and perfume. Or they may fail to register as anything but misshapen chunks of resin.