Where History, Science, and Coral Reef Conservation Meet: A Case Study from St John, U.S. Virgin Islands

Latin American Studie

Editorial

Hydro-geomorphology as a central theme in environmental studie

On the hydro-geomorphology of steepland coffee farming: Runoff and surface erosion

Soil compaction and natural vegetation removal associated to agriculture tends to promote runoff and soil erosion with potentially adverse onsite, downstream, and global impacts. Although coffee farming represents a fraction of the world’s harvested lands, it is a vital crop for many developing nations where it is frequently cultivated on erosion prone, high-relief, wet tropical landscapes. However, limited empirical data exists on coffee farm erosion. This article attends this need by describing the results of rainfall simulation experiments designed to evaluate the impact of sun-grown coffee-farming on precipitation excess, soil infiltration rates, and surface erosion by overland flow. Results show that infiltration rates on coffee-cultivated fields are ∼60 – 80% relative to undisturbed forested slopes, and that cultivation increases erosion rates by one to two orders of magnitude depending on the presence or absence of mulch or weed cover. The magnitude of the impact suggests that erosion on coffee-cultivated land is unsustainable from both a soil formation and an agricultural productivity point of view. Unsurfaced access roads display an even greater impact than cultivated surfaces with infiltration rates ∼10% of undisturbed soils and erosion up to four-orders of magnitude above background depending on grading history and slope. Farm-scale annualized erosion is ∼3–24 Mg ha-1 yr-1 depending on actively used unpaved road abundance as roads account for ∼99% of net erosion. Implementing efficient erosion control strategies for coffee farms is therefore essential to reduce their current impacts, but also for the future given the worldwide surge in coffee harvesting areas projected for the upcoming decades

Effects of Hillslope Trenching on Surface Water Infiltration in Subalpine Forested Catchments

Concerns over freshwater scarcity for agriculture, ecosystems, and human consumption are driving the construction of infiltration trenches in many mountain protected areas. This study examines the effectiveness of infiltration trenches in a subalpine forested catchment in central Mexico, where public and private organizations have been constructing trenches for ~60 years. We rely on empirical data to develop rainfall-runoff models for two scenarios: a baseline (no trenches) and a trenched scenario. Field measurements of infiltration capacities in forested and trenched soils (n = 56) and two years of meteorological data are integrated into a semi-distributed runoff model of 28 trenched sub-catchments. Sensitivity analysis and hydrographs are used to evaluate differences in total runoff and infiltration between the two scenarios. Multiple logistic regression is used to evaluate the effects of environmental and management variables on the likelihood of runoff response and trench overtopping. The findings show that soil infiltration capacity and rainfall intensity are primary drivers of runoff and trench overtopping. However, trenches provided only a 1.2% increase in total infiltration over the two-year period. This marginal benefit is discussed in relation to the potential adverse environmental impacts of trench construction. Overall, our study finds that as a means of runoff harvesting in these forested catchments, trenches provide negligible infiltration benefits. As a result, this study cautions against further construction of infiltration trenches in forested catchments without careful ex ante assessment of rainfall-runoff relationships. The results of this study have important implications for forest water management in Mexico and elsewhere, where similar earthworks are employed to enhance runoff harvesting and surface water infiltration

A Catalogue of Tropical Cyclone Induced Instantaneous Peak Flows Recorded in Puerto Rico and a Comparison with the World’s Maxima

Peak streamflow rates from the Insular Caribbean have received limited attention in worldwide catalogues in spite of their potential for exceptionality given many of the islands’ steep topographic relief and proneness to high rainfall rates associated with tropical cyclones. This study compiled 1922 area-normalized peak streamflow rates recorded during tropical cyclones in Puerto Rico from 1899 to 2020. The results show that the highest peak flow values recorded on the island were within the range of the world’s maxima for watersheds with drainage areas from 10 to 619 km2. Although higher tropical cyclone rainfall and streamflow rates were observed on average for the central–eastern half of Puerto Rico, the highest of all cyclone-related peaks occurred throughout the entire island and were caused by tropical depressions, tropical storms, or hurricanes. Improving our understanding of instantaneous peak flow rates in Puerto Rico and other islands of the Caribbean is locally important due to their significance in terms of flooding extent and its associated impacts, but also because these could serve as indicators of the implications of a changing climate on tropical cyclone intensity and the associated hydrologic response

Watershed- and island wide-scale land cover changes in Puerto Rico (1930s-2004) and their potential effects on coral reef ecosystems

Anthropogenically enhanced delivery of sediments and other land-based sources of pollution represent well-recognized threats to nearshore coral reef communities worldwide. Land cover change is commonly used as a proxy to document human-induced alterations to sediment and pollutant delivery rates to coral reef bearing waters. In this article, land cover change was assessed for a 69-km² watershed in Puerto Rico between 1936 and 2004 by aerial photograph interpretation. Forests and sugar cane fields predominated from 1936 through the late 1970s, but while cropland dipped to negligible levels by 2004, net forest cover doubled and built-up areas increased tenfold. The watershed-scale land cover changes documented here mimicked those of the entire Puerto Rican landmass. Sediment yield predictions that rely on the sort of land cover changes reported here inevitably result in declining trends, but anecdotal and scientific evidence in the study watershed and throughout Puerto Rico suggests that sediment and pollutant loading rates still remain high and at potentially threatening levels. The simultaneous reduction in living coral cover that accompanied reforestation and urbanization patterns since the 1970s in our study region is discussed here within the context of the following non-mutually exclusive potential explanations: (a) the inability of land cover change-based assessments to discern spatially-focused, yet highly influential sources of sediment; (b) the potentially secondary role of cropland and forest cover changes in influencing nearshore coral reef conditions relative to other types of stressors like those related to climate change; and (c) the potentially dominant role that urban development may have had in altering marine water quality to the extent of reducing live coral cover. Since identification of the causes for coral reef degradation has proven elusive here and elsewhere, we infer that coral reef management may only be effective when numerous land- and marine-based stressors are simultaneously mitigated.11 page(s

Preliminary Analyses of the Hydro-Meteorological Characteristics of Hurricane Fiona in Puerto Rico

The Caribbean has displayed a capacity to fulfill climate change projections associated with tropical cyclone-related rainfall and flooding. This article describes the hydrometeorological characteristics of Hurricane Fiona in Puerto Rico in September 2022 in terms of measured and interpolated rainfall and observed peak flows relative to previous tropical cyclones from 1899 to 2017. Hurricane Fiona ranks third overall in terms of island-wide total rainfall and fourth in terms of daily rainfall. Maximum daily rainfall during Hurricane Fiona exceeded those previously reported (excluding Hurricane María in 2017) in the eastern interior and eastern portions of the island. In terms of peak flows, no value approached the world’s or Puerto Rico’s flood envelope, although 69% of the observations are considered ‘exceptional’. About 26% and 29% of all peak flows were in the 5–10 year and 10–25 year recurrence interval ranges, respectively, yet none matched the 25-year levels. The highest peak flows were concentrated in the central-eastern and southeastern regions. Even though Hurricane María provoked a more extreme hydrometeorological response, some of Hurricane Fiona’s hydro-meteorological characteristics were among the highest ever recorded in Puerto Rico, particularly for the south-central and eastern portions of the island, and it displayed the island’s current level of vulnerability to extreme rainfall