Robert Stallard has been at the USGS since 1987 and is now a Scientist Emeritus in the Hydro-Eco Interactions Branch of the Earth Systems Processing Division of the USGS Water Resources Mission Area.
Robert Stallard has been at the USGS since 1987 and is now a Scientist Emeritus in the Hydro-Eco Interactions Branch of the Earth Systems Processing Division of the Water Mission Area. He studies how land-cover and climate change affect water movement through soils, weathering, and erosion, and how these, in turn, affect the composition and dispersal of dissolved and solid phases in rivers and trace gases in the atmosphere. Areas of expertise include surface-water hydrology, major element and nutrient biogeochemistry, soil formation and sediment genesis, vegetation-landscape interaction, carbon-cycle characterization on land and in the ocean, and assessment of land-use and climate change. His work has included the study of natural and human-altered landscapes, in the Americas, Southeast Asia, and Africa, including large parts of the Amazon, Orinoco, Mississippi, and Panama Canal Basins and eastern Puerto Rico.
Most of his current efforts are committed to a multi-catchment investigations designed to distinguish the roles of vegetation, climate, and land-cover change and to put this in a hydrologic and biogeochemical framework as well as to examine ecosystem costs and services focusing on water, carbon, and biodiversity. Two projects currently consume most of his USGS time: (1) Work related to the Luquillo USGS Water, Energy, and Biogeochemical Budget (WEBB) Project in eastern Puerto Rico and parallel work in Panama, which has as a goal the comprehensive assessment of catchment hydrology and biogeochemistry in a hydrologically energetic landscapes. (2) The Agua Salud Project in the Central Panama Canal Basin examines the manifold effects of different styles of reforestation as compared to mature forested and deforested catchments. The project started in 2008 and involves 13 small watersheds with different land covers.
- National Research Council Post-Doctoral Fellowship: 1981, At the U.S. Geological Survey - Office of Marine Geology, Woods Hole, MA. Clay mineralogy of the Amazon River system.
- Ph.D., Chemical Oceanography: 1980, Massachusetts Institute of Technology - Woods Hole Oceanographic Institution Joint Program in Oceanography. Ph.D. thesis entitled "Major Element Geochemistry of the Amazon River System."
- B.S., Earth & Planetary Sciences: 1974, Massachusetts Institute of Technology. Emphasis in Planetary Physics and Chemistry.
Science and Products
Extreme rainstorms drive exceptional organic carbon export from forested humid-tropical rivers in Puerto Rico
The influence of land cover and storm magnitude on hydrologic flowpath activation and runoff generation in steep tropical catchments of central Panama
Precipitation characteristics and land cover control wet season runoff source and rainfall partitioning in three humid tropical catchments in central Panama
Assessing plot-scale impacts of land use on overland flow generation in Central Panama
Clarifying regional hydrologic controls of the Marañón River, Peru through rapid assessment to inform system-wide basin planning approaches
Reassessing rainfall in the Luquillo Mountains, Puerto Rico: Local and global ecohydrological implications
Land use history and population dynamics of free-standing figs in a maturing forest
Formation of the Isthmus of Panama
Comments to Middle Miocene closure of the Central American Seaway
Implications of climate and land use change
Introduction to watershed ecosystem services: Chapter 1
Understanding natural capital
Geospatial data for Luquillo Mountains, Puerto Rico: Mean annual precipitation, elevation, watershed outlines, and rain gage locations
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Extreme rainstorms drive exceptional organic carbon export from forested humid-tropical rivers in Puerto RicoExtreme rainfall events in the humid-tropical Luquillo Mountains, Puerto Rico export the bulk of suspended sediment and particulate organic carbon. Using 25 years of river carbon and suspended sediment data, which targeted hurricanes and other large rainstorms, we estimated biogenic particulate organic carbon yields of 65 ± 16 tC km−2 yr−1 for the Icacos and 17.7 ± 5.1 tC km−2 yr−1 for the Mameyes
The influence of land cover and storm magnitude on hydrologic flowpath activation and runoff generation in steep tropical catchments of central PanamaDespite abundant research documenting that land use/land cover (LULC) have substantial impacts on the hydrology of humid tropical systems, field-based evidence for the physical mechanisms behind these impacts are still lacking. In particular, our understanding of the hydrologic flowpaths that generate runoff in these systems, and how they vary with respect to LULC is insufficient to inform both ph
Precipitation characteristics and land cover control wet season runoff source and rainfall partitioning in three humid tropical catchments in central PanamaMechanisms of runoff generation in the humid tropics are poorly understood, particularly in the context of land-use/land cover change. This study analyzed the results of 124 storm hydrographs from three humid tropical catchments of markedly different vegetation cover and land-use history in central Panama during the 2017 wet season: actively grazed pasture, young secondary succession, and near-mat
Assessing plot-scale impacts of land use on overland flow generation in Central PanamaLand use in Panama has changed dramatically with ongoing deforestation and conversion to cropland and cattle pastures, potentially altering the soil properties that drive the hydrological processes of infiltration and overland flow. We compared plot-scale overland flow generation between hillslopes in forested and actively cattle-grazed watersheds in Central Panama. Soil physical and hydraulic pro
Clarifying regional hydrologic controls of the Marañón River, Peru through rapid assessment to inform system-wide basin planning approachesWe use remote sensing to enhance the interpretation of the first baseline dataset of hydrologic, isotopic and hydrochemical variables spanning 620 km of the upper Marañón River, in Andean Peru, from the steep alpine canyons to the lower lying jungle. Remote, data-scarce river systems are under increased hydropower development pressure to meet rising energy demands. The upstream-downstream river co
Reassessing rainfall in the Luquillo Mountains, Puerto Rico: Local and global ecohydrological implicationsMountains receive a greater proportion of precipitation than other environments, and thus make a disproportionate contribution to the world’s water supply. The Luquillo Mountains receive the highest rainfall on the island of Puerto Rico and serve as a critical source of water to surrounding communities. The area’s role as a long-term research site has generated numerous hydrological, ecological, a
Land use history and population dynamics of free-standing figs in a maturing forestFigs (Ficus sp.) are often considered as keystone resources which strongly influence tropical forest ecosystems. We used long-term tree-census data to track the population dynamics of two abundant free-standing fig species, Ficus insipida and F. yoponensis, on Barro Colorado Island (BCI), a 15.6-km2 island in Lake Gatún, Panama. Vegetation cover on BCI consists of a mosaic of old growth (>400 year
Formation of the Isthmus of PanamaThe formation of the Isthmus of Panama stands as one of the greatest natural events of the Cenozoic, driving profound biotic transformations on land and in the oceans. Some recent studies suggest that the Isthmus formed many millions of years earlier than the widely recognized age of approximately 3 million years ago (Ma), a result that if true would revolutionize our understanding of environmenta
Comments to Middle Miocene closure of the Central American SeawayIn a recent paper proposing an early (mid-Miocene) closure of the Central American Seaway (CAS), Montes et al. 2015 (1) disregard existing paleogeographic data that invalidate Panama as a source for zircons, and inappropriately ignore the evidence for trans-isthmian marine connections until 4-3 Ma. They also fail to cite previous work (2, 3), that had reconstructed the Central American arc already
Implications of climate and land use changeThis chapter relates ecosystem services to climate change and land use. The bulk of the chapter focuses on ecosystem services and steepland land use in the humid Neotropics – what is lost with land-cover changed, and what is gained with various types of restoration that are sustainable given private ownership. Many case studies are presented later in the white paper. The USGS contribution relates
Introduction to watershed ecosystem services: Chapter 1Humans derive a great number of goods and services from terrestrial ecosystems (Millennium Ecosystem Assessment, 2003, 2005). Some, like timber, fruits, bush meat, and other forest based food stuffs, are evident but others are not so obvious. Increasingly policy makers have realized the importance of forests and other ecosystems in sequestering carbon, as clearing of once vibrant vegetation or dra
Understanding natural capitalThis chapter serves to introduce the geophysics of Neotropical steeplands. Topics are covered in a general manner with hyperlinks to active research and monitoring sites (such as the National Hurricane Center and US Geological Survey publication). Topics covered include ‘tropical climate and weather,’ ‘climate variations and trends,’ Neotropical ‘geology, and soils,’ ‘hillslopes and erosion,’ ‘lak
Geospatial data for Luquillo Mountains, Puerto Rico: Mean annual precipitation, elevation, watershed outlines, and rain gage locationsThese geospatial data sets were developed as part of a new analysis of all known current and historical rain gages in the Luquillo Mountains, Puerto Rico published in the journal article Murphy, S.F., Stallard, R.F., Scholl, M.A., Gonzalez, G., and Torres-Sanchez, A.J., 2017, Reassessing rainfall in the Luquillo Mountains, Puerto Rico: Local and global ecohydrological implications: PLOS One 12(7):