For the first time in more than half a century, a joint Cuban/American science team has worked
together to quantify the impacts of chemical weathering and sustainable agriculture on river
water quality in Cuba—the largest and most populous Caribbean island. Such data are critical as
the world strives to meet sustainable development goals and for understanding rates of landscape
change in the tropics, an understudied region. To characterize the landscape, we collected and
analyzed water samples from 25 rivers in central Cuba where upstream land use varies from
forested to agricultural.
Cuban river waters bear the fingerprint of the diverse rock types underlying the island, and many
carry exceptionally high dissolved loads. Chemical denudation rates are mostly among the top 25%
globally and are similar to those measured in other Caribbean islands. High rates of solute
export and the distinct composition of the waters in specific basins suggest flow paths that
bring river source waters into contact with fresh, weatherable rock—unusual in a warm, wet,
tropical climate where weathering should extend deep below the surface. Tectonically driven
uplift likely maintains the supply of weatherable material, leading to channel incision and,
thus, to the exposure of bedrock in many river channels.
Despite centuries of agriculture, the impact on these rivers’ biogeochemistry is limited.
Although river water in many central Cuban rivers has high levels of E. coli bacteria,
likely sourced from livestock, concentrations of dissolved nitrogen are far lower than other
areas where intensive agriculture is practiced, such as the Mississippi River Basin. This
suggests the benefits of Cuba’s shift to conservation agriculture after 1990 and provides a
model for more sustainable agriculture worldwide.
Manuscript received 17 July 2019. Revised manuscript received 17 Dec. 2019.
Manuscript accepted 20 Dec. 2019. Posted 30 Jan. 2020.
© The Geological Society of America, 2020. CC-BY-NC.