Research

As a conservation scientist, I use the tools of geospatial analysis, ecology, and environmental science to investigate what a changing agricultural footprint means for the natural world. To a large degree, the fate of the natural world depends on how we humans go about feeding ourselves. We already collectively use nearly 40% of the earth’s ice-free land for agriculture, and agriculturally-driven habitat loss remains the largest threat to species, even while climate change and overexploitation make things even more difficult for wildlife.

Agriculture’s footprint is currently in a state of flux, with some places experiencing agricultural expansion and intensification to meeting rising demands while others experience abandonment as people move and the economics of farming change due to demographic, technological, and environmental changes. I’m motivated by a desire to find opportunities to conserve biodiversity throughout these agricultural transitions, whether that means helping guide expansion in order to minimize impact or fostering a return of nature following abandonment.

My research has focused on questions related to the environmental trade-offs these transitions present:

  • Where does cropland abandonment occur and to what extent is it durable?
  • Where will these transitions present opportunities for habitat regeneration in former croplands, and how might policies be designed to harness these opportunities and encourage regeneration?
  • In places where agricultural expansion is necessary, can spatial land-use prioritization tools help minimize biodiversity loss?

My work has been published in journals such as Science Advances and Ecological Applications, and covered by outlets like BioScience, Bloomberg, and The Hill. Read on for more details on some of my most recent projects.

Using metrics of biodiversity to minimize the impact of agricultural expansion

How does the way we measure biodiversity affect which spaces we choose to farm and which we choose to protect? With agricultural demands on the rise, it’s even more important than ever to be strategic about how we use land and answer the question of “where to put things” (in the words of Polasky et al. 2008). One of the ways to do this is through land-use prioritization, the process of using models to ask: in places where food production must rise, which spaces should we convert to agriculture in order to meet agricultural needs, while minimizing impacts on biodiversity and the environment?

These tools require some way to measure biodiversity alongside agricultural productivity, usually through some sort of biodiversity index, a single value representing the relative biodiversity value of each point on a map. But measuring “biodiversity” is incredibly difficult, and many different decisions go into the construction of a biodiversity index, in terms of what is valued and how it’s valued - all of which affect land-use decisions. One index might prioritize certain groups of species (maybe they really, really like birds). Another might prioritize species based on range size (smaller-ranged species are more likely at risk). Others use different methods to combine multiple factors into a single index.

In this project, we collected a range of recently published biodiversity indices and ran them through a prioritization model designed for Zambia and developed by my stellar coauthors Lyndon Estes (Clark University) and Tim Searchinger (Princeton University and WRI). We tested how differences in these metrics affected where the model recommended future agricultural conversion take place, showing that different biodiversity metrics produced land-use recommendations that overlapped in only about 4% of places selected for agricultural expansion (or less). By testing a range of permutations, we found that some decisions played a larger role: for example, the group of species had a larger effect than the method used to combine factors. But even small, frequently ignored methodological differences can produce very different maps. While no single metric works in all situations, our results highlight the importance of working towards a more consistent framework for prioritizing biodiversity in different contexts. Small differences in biodiversity metrics can have profound impacts on the natural world. This is even more important as the international community searchers for ways to measure changes in biodiversity, especially for potential markets in biodiversity credits.

This project was published in Ecological Applications in 2021 and was featured in an article by Carolyn Beans in BioScience.

Quantifying the environmental consequences of recent cropland abandonment

Though agriculture continues to expand in many places, tens of millions of hectares of croplands have been abandoned across the world in recent decades as people in rural areas moved into cities in pursuit of better economic opportunities, and agriculture has been reshaped by environmental, economic, and sociopolitical upheaval. Abandonment is likely to continue for many years due to broad economic and demographic changes, presenting a substantial sources of land that could be used for land-based climate mitigation or ecosystem restoration without imposing significant opportunity costs. Could this create opportunities to restore ecosystems while storing carbon and recovering wildlife in the process?

Tracking the persistence of recent cropland abandonment to understand its implications for biodiversity and carbon sequestration

Historically, it has been really difficult to track agricultural abandonment through time at meaningful scales, limiting our ability to answer questions about what abandonment is likely to mean for the environment. However, recent advances in remote sensing have made it possible to track abandonment across broad areas, which is where two of my excellent collaborators come in: together with researchers at the University of Wisconsin-Madison, He Yin (Kent State University) and Volker Radeloff (University of Wisconsin-Madison) developed a new method to produce a cutting-edge land cover time-series from 30m Landsat imagery. Using this time-series, we were able to track the outcomes of abandonment at 11 sites covering four continents and a range of different biomes. We found lots of abandonment: nearly 40% of all croplands cross our sites were abandoned at least once between 1987-2017. But abandonment was dynamic, and 31% of these abandoned croplands were recultivated before the end of the time series. This means less area for new wildlife habitat & less carbon sequestered as ecosystems regenerate. These abandoned croplands accumulated 110 million tons of carbon by 2017, yet this was 35% less that what could have accumulated if no recultivation had occurred. Given that abandonment is a dynamic process, with various croplands going in & out of cultivation at different times over the course of the time series, we developed linear models to predict how long abandoned croplands would be abandoned as a function of time. At most sites, we predict that >50% of abandoned croplands will be recultivated within 30 years. For many ecosystems, it can take >50 years to recover the species communities & carbon levels of similar intact ecosystems. Without incentives for restoration, cropland abandonment rarely lasts long enough to yield biodiversity or carbon benefits.

This project was published in Science Advances in 2022, and covered by Bloomberg, The Hill, Princeton University, and Clark University.

Investigating the effect of cropland abandonment individual species of birds and mammals

Abandonment has excited environmentalists and climate advocates for its potential to restore ecosystems and provide nature-based carbon sequestration opportunities, but conservation biologists sometimes disagree about whether abandonment is likely to benefit or harm biodiversity overall. Due to variation in the distribution of species and their habitats, the landscape changes that accompany abandonment are certain to benefit some species more than others; for example, a transition from an agricultural landscape to forest is likely to benefit forest birds, while open-habitat specialists are more likely to decline. Along with the difficulty of tracking abandonment through time and space, this variation in species-responses to abandonment has led to uncertainty and controversy over whether to try to prevent abandonment or accept and sometimes encourage regeneration after abandonment. In this project, we combined our cutting-edge land cover time series with habitat and distribution data for >2000 species of birds and mammals to investigate how abandonment, secondary succession, and recultivation affected the area of habitat available for individual species of birds and mammals. Our results indicate that cropland abandonment resulted in habitat gains for the majority of species at our sites, but rarely compensated for habitat loss due to other factors, particularly ongoing habitat loss and recultivation of abandoned lands. Despite the substantial potential for abandonment to benefit the species we considered, limiting recultivation and reducing habitat loss remains critical for the future of biodiversity. We’re wrapping this work up now, so stay tuned for a forthcoming publication.