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¡Cuba! River Water Chemistry Reveals Rapid

Chemical Weathering, the Echo of Uplift, and

the Promise of More Sustainable Agriculture

Paul Bierman, Dept. of Geology and Gund Institute for Environment, University of Vermont, Burlington, Vermont 05405, USA; Rita Yvelice
Sibello Hernández, Centro de Estudios Ambientales de Cienfuegos, Cienfuegos, Cuba; Amanda H. Schmidt, Geology Dept., Oberlin
College, Oberlin, Ohio 44074, USA; Héctor Alejandro Cartas Aguila, Yoelvis Bolaños Alvarez, Aniel Guillén Arruebarrena, Centro de
Estudios Ambientales de Cienfuegos, Cienfuegos, Cuba; Mae Kate Campbell, Dept. of Geology and Gund Institute for Environment,
University of Vermont, Burlington, Vermont 05405, USA; David Dethier, Geosciences Dept., Williams College, Williamstown, Massachusetts
01267, USA; Monica Dix, Geology Dept., Oberlin College, Oberlin, Ohio 44074, USA; Marika Massey-Bierman, Geosciences Dept.,
Williams College, Williamstown, Massachusetts 01267, USA; Alejandro García Moya, Centro de Estudios Ambientales de Cienfuegos,
Cienfuegos, Cuba; Julia Perdrial, Dept. of Geology and Gund Institute for Environment, University of Vermont, Burlington, Vermont 05405,
USA; Jason Racela, Geosciences Dept., Williams College, Williamstown, Massachusetts 01267, USA; Carlos Alonso-Hernández, Centro de
Estudios Ambientales de Cienfuegos, Cienfuegos, Cuba

ABSTRACT concentrations of dissolved nitrogen are far central Cuba, the result of a bi-national, col-
For the first time in more than half a cen- lower than other areas where intensive agri- laborative field campaign. Biogeochemical
tury, a joint Cuban/American science team culture is practiced, such as the Mississippi analyses allow us to address fundamental
has worked together to quantify the impacts River Basin. This suggests the benefits of geologic questions, such as the pace of
of chemical weathering and sustainable agri- Cuba’s shift to conservation agriculture after chemical weathering in the tropics, as well
culture on river water quality in Cuba—the 1990 and provides a model for more sustain- as applied environmental questions related
largest and most populous Caribbean island. able agriculture worldwide. to the quality of river water and human
Such data are critical as the world strives to impacts on a landscape where small-scale,
meet sustainable development goals and for INTRODUCTION sustainable farming has replaced substan-
understanding rates of landscape change in The Republic of Cuba (Fig. 1) has more tial swaths of industrial agriculture (The
the tropics, an understudied region. To char- than 11 million inhabitants, but there has Guardian, 2017).
acterize the landscape, we collected and ana- been little collaboration between U.S. and
lyzed water samples from 25 rivers in central Cuban scientists for more than half a cen- BACKGROUND AND METHODS
Cuba where upstream land use varies from tury although only 160 km separates the Cuba’s wet, warm tropical landscape is
forested to agricultural. two countries (Feder, 2018). River biogeo- dominated by mountains (up to 1917 m
Cuban river waters bear the fingerprint chemistry data, which are sparse in tropical above sea level [asl] in the east, 500–700 m
of the diverse rock types underlying the regions, are needed to guide sustainable asl elsewhere) running parallel to the north
island, and many carry exceptionally high development in Cuba and, by example, in and south coasts (Fig. 1). Mainly forested
dissolved loads. Chemical denudation rates other tropical and island nations. uplands descend into farmed rolling plains
are mostly among the top 25% globally and Here, we present and interpret extensive and mangrove-lined, low-lying coastal
are similar to those measured in other new data characterizing river waters in estuaries. The climate is summer-wet and
Caribbean islands. High rates of solute
export and the distinct composition of the
waters in specific basins suggest flow paths Elevation [m]
that bring river source waters into contact 1900 m ¹
with fresh, weatherable rock—unusual in a
warm, wet, tropical climate where weather- 0 m
ing should extend deep below the surface. 90°W 70°W
Tectonically driven uplift likely maintains 30°N
the supply of weatherable material, leading United States Guadeloupe
to channel incision and, thus, to the expo- Dominica
sure of bedrock in many river channels. Martinique
Despite centuries of agriculture, the Cuba 20°N
impact on these rivers’ biogeochemistry is Mexico Jamaica 0 100 200 Km
limited. Although river water in many cen- Dominican Republic
tral Cuban rivers has high levels of E. coli Figure 1. Cuba with elevation as color ramp. Black outline is area mapped in Figure 3. Inset shows loca-
bacteria, likely sourced from livestock, tion of Cuba in relation to North America.

4 GSA Today | March-April 2020

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