September 1, 2014

Shelby Hayhoe-Riskin Defends Dissertation

May 30, 2012

Shelby in a Brazilian Stream. Photo by Chris Neill.

Deep soils that strongly bind phosphorus fertilizer buffer streamwater against changes to dissolved nutrient concentrations across wide areas of the Amazon rainforest that have been recently converted to intensive soybean agriculture, Brown-MBL student Shelby Riskin showed in new research. Riskin, who defended her PhD dissertation on May 30, spent the last five years comparing soils and waters in small forest and soybean watersheds in the Brazilian state of Mato Grosso, where the area of soybean farms has exploded since the early 2000s.

One of Riskin’s main findings is that the flow of water out of small streams in soybean fields increases four-fold because of the loss of evapotranspiration through the leaves of the original forest trees. But that change was not accompanied by increased “flashiness,” or flows of streamwater during storms. That’s because even under intensive cropping, the high permeability of soils allows water to infiltrate directly to groundwater without running overland. So even though more water reaches streams, it arrives in a very even flow controlled by release from groundwater. Because soils over the majority of the new soybean farming region are very deep as well as highly permeable, this allows water to contact soils along very long pathways that further buffer streamwater against changes in dissolved nutrients. “Soils play a critical role in regulating the way that intensive farming systems affect surface waters,” Riskin said, “and those effects may not follow the same patterns that we observe in intensively-farmed areas of temperate regions.”

Riskin analyzed the potential role of soils in controlling both the need for fertilizer and impacts to surface waters in the world’s three largest intensive soybean farming systems in Brazil, Iowa and Argentina. Compared with Iowa and Argentina, the large amounts of phosphorus fertilizer used to overcome the low native fertility of Brazilian Amazon rainforest soils are less likely to move to stream and cause nutrient overenrichment and algae blooms that compromise water quality because the Amazon soils bind phosphorus so tightly and permeable soils resist erosion. But the flip side to all that phosphorus retention is that Amazon soybeans will need high rates of fertilization for many years into the future because soils bind phosphorus so tightly it becomes relatively unavailable to the soybean crop. As crop agriculture on cleared rainforest soils expands around the world on high phosphorus-binding soils, the global demand for phosphorus fertilizer is likely to soar. Because relatively few countries control the vast majority of mineable phosphorus fertilizer is mined in relatively few countries (Morocco, China and Algeria have the world’s largest reserves).

Riskin worked at Tanguro Ranch, a 200,000-acre soybean farm in the headwater region of the Xingu River watershed in central Brazil. She was advised by Chris Neill at MBL and Stephen Porder at Brown. Her work was supported by grants from the National Science Foundation and the Mellon Foundation, a Watson Fellowship from MBL and a Cogut Fellowship from the Center for Latin American and Caribbean Studies at Brown.

Brown MBL Students Receive Fellowships

Several Brown-MBL Graduate Students received prestigious fellowships in Spring 2012.

Lindsay Brin, a fourth year graduate student advised by Anne Giblin at MBL and Jeremy Rich at Brown, received the Watson Fellowship in Environmental Sciences.  Lindsay studies how temperature and organic matter availability affect the balance of nitrogen that is removed from or recycled within coastal ecosystems.


Chelsea Nagy, a second year graduate student advised by Chris Neill at MBL and Stephen Porder at Brown, received a three year EPA Star  (Science to Achieve Results) Research Award.  Chelsea studies how land-use changes impact forest health in the Amazon soybean-growing region of Brazil.


Victor Schmidt, a first year graduate student advised by Kate Smith at Brown and Linda Amaral Zettler at MBL,received the Crane Family Global Infectious Disease Fellowship. Victor studies how microbial community shifts can influence disease development, pathogen transmission,  and human and ecosystem health.


3 Day January 2013 Workshop: Intensifying Agriculture: Environmental Impacts and Potential Solutions

A three-day interdisciplinary workshop focused on intensive agriculture was held at MBL January 14- 16, 2013.

To meet the demands of a growing global population and shifting diets, the extent of agricultural land and productivity of existing land is increasing. This intensification of agriculture has unintended but profound effects on local and global environments. Natural and social scientists at Brown and the Marine Biological Laboratory have begun to describe these consequences, to understand social and biological drivers, and to develop solutions to issues associated with intensified agriculture.

This workshop will gather an interdisciplinary group of faculty, postdocs, and graduate students from Brown, MBL, our NSF PIRE project collaborators at Columbia, and other institutions to synthesize our understanding of the environmental impacts and solutions of intensified agricultural practices. The main objectives of the workshop are to review the state of knowledge of agriculture’s environmental impact, to identify knowledge gaps, and to stimulate new ideas for interdisciplinary research. We will explore the idea of putting together a special journal issue. Additionally, the workshop is intended to build and strengthen collaborations and identify avenues for future research.

To register for the workshop or to find more information, please click here and then choose ‘Registration Information’.

Please register by November 15, 2012 to guarantee your spot

Contact Rebecca Ryals at with any questions.

January Brown-MBL Course: Statistical Analysis & Graphics with R

A Brown-MBL course, “Statistical Analysis and Graphics with R”, was offered at MBL in Woods Hole January 7-22, 2013 with Dr. Erika Sudderth of Brown University. The primary aim of this course was to learn methods in R for data manipulation, analysis, and graphical presentation. 20 students attend the intensive 12 day course.

IGERT Program


Brown and MBL recently received a joint IGERT: Reverse Ecology grant from the National Science Foundation to support a program to train PhDs at the interface of computational biology, genomics and environmental science.

“Reverse Ecology” is the practice of inferring ecological and evolutionary information about organisms and communities from genes and gene sequences in their DNA.

The IGERT program emphasizes training students in the use of powerful, new genomic approaches that allow the identification of genetic bases of natural functional variation in the environment. Students learn to carry out every step of the process, from DNA extraction to computer analysis of sequence data.

Program Highlights

1. A year long immersion course focused at Long Term Ecological Research sites where students design an experiment and use high-throughput genomic and computational strategies to test hypotheses, with the goal of preparing and submitting a multi-authored journal article.

2. Jointly-mentored research rotations where students and faculty cross disciplinary boundaries.

3. Career training that integrates grant writing, public speaking, ethics, diversity and international.

There are currently three students in the IGERT program and at least three more will join the program in the fall.

Please click here for more information.


PIRE: Partnership for Integrated Graduate Study in Africa

New Opportunity for Graduate Study: Human Well-being and the Environment in Africa

The Environmental Change Initiative at Brown University, the Earth Institute at Columbia University, the Ecosystems Center of the Marine Biological Laboratory in Woods Hole, Moi University in Kenya, and Sokoine University in Tanzania offer graduate fellowships at Brown and Columbia in an exciting new cross-cutting natural and social science Partnership for International Research and Education (PIRE) project in Africa. The project will examine how agricultural interventions designed to increase crop yields in African Millennium Villages influence land-use patterns and the degradation or enhancement of soils, biodiversity and other ecosystem services and human wellbeing at both local and regional scales.

We seek PhD students who will pursue research in Africa in the fields of remote sensing, ecology, sociology or economics and who desire training that cuts across traditional disciplinary boundaries and who want to apply their work to pressing problems of human welfare and the environment. Students will enroll in the Departments of Ecology and Evolutionary Biology, Geological Sciences, Sociology or Economics at Brown or the Departments of Ecology, Evolution and Environmental Biology, Earth and Environmental Sciences or the PhD program in Sustainable Development at Columbia. PIRE students will work with teams of mentors at Brown, Columbia and MBL and collaborate with faculty partners at Moi and Sokoine Universities.


Downloads: (pdf format) Full Project Description 1-Page Flyer

Contacts: Contact faculty directly, or the people below for more information:

Sara Lizzo at Columbia University, 212-851-5833, sel2139 at

Martha Downs at Brown University 401-863-3493, Martha_Downs at

Jill Holdren at the Marine Biological Laboratory 508-289-7715, jholdren at