About

Oswald J. Schmitz is the Oastler Professor of Population and Community Ecology at Yale University School of the Environment. His research focuses on the linkage between biodiversity and ecosystem services, examining how predator and herbivore species influence plant species composition and productivity, as well as ecosystem processes such as nutrient and carbon cycling. He studies how environmental disturbances like global climate change and natural resource exploitation alter species interactions and ecosystem services, aiming to inform conservation strategies by considering species as part of a natural portfolio of management options. His work employs field experimentation guided by formal mathematical theory of species interactions to identify functionally unique predator and herbivore groupings and their causal effects on ecosystems. Schmitz has authored the book 'The New Ecology: Rethinking a Science for the Anthropocene,' which makes ecological science accessible to a broader audience and is heavily inspired by Aldo Leopold's writings.

Research topics

• Ecology
• Biology
• Geography
• Environmental science

Selected publications

• Consumers show flexible refuge use but more rigid foraging under plant invasion

  Biological Invasions · 2026-04-01

  article
  PublisherDOI

• Author response for "Ecosystem effects of predators are amplified across generations through prey behavioral plasticity"

  2025-10-06

  peer-reviewSenior author
  PublisherDOI

• Ecosystem Effects of Predators Are Amplified Across Generations Through Prey Behavioural Plasticity

  Ecology Letters · 2025-11-01

  articleSenior author

  Predator-induced changes in prey traits can cascade through ecosystems to impact biogeochemical cycling and community structure. Whether these effects persist, amplify or diminish across prey generations remains uncertain. We tested for predator transgenerational effects using a 3-year common garden experiment in a terrestrial old-field ecosystem. Predator exposure was manipulated across two generations of four grasshopper herbivore prey populations, with measurements of ecosystem processes made alongside measurements of prey trait responses. We found predators had larger effects on plant community biomass, plant diversity and soil carbon accumulation in the second generation of predator exposure than in the first generation. Paired with trait data on the grasshoppers, we found this amplification of ecosystem effects corresponded with heightened antipredator behaviours in the second generation. Our results show that transgenerational behavioural plasticity can magnify predator-driven ecosystem impacts across generations, linking eco-evolutionary processes with ecosystem dynamics.

  PublisherDOI

•  A social-ecological study of a Costa Rica fishery through fisher local ecological knowledge and satellite tracking

  2025-03-26

  preprintOpen access

  Local ecological knowledge (LEK) is increasingly being recognized as a valuable component of ecological modeling, including in the creation of species distribution models (SDMs). SDMs are used to make inferences about the distribution of suitable habitat for species of interest and can provide valuable information about the occurrence of these species. However, data and monitoring limitations can be especially pronounced in remote areas, creating a need for affordable, reliable, and timely information. In fisheries studies, incorporating LEK from fishers may be a valuable way to fill data gaps in predicting fish species occurrence over spatiotemporal scales and can be useful for marine spatial planning. In this study, we investigated the spatiotemporal and biophysical characteristics of a billfish fishery in Costa Rica through a mixed methods approach combining satellite tracking data of sailfish (Istiophorus platypterus) and blue marlin (Makaira nigricans) and sport fisher LEK elicited through semi-structured interviews and participatory mapping. To compare these two methods for understanding billfish distribution, we created SDMs using either satellite tag data or LEK participatory maps for billfish occurrences and examined the environmental profiles within the satellite tracking and participatory map locations. Overall, we found that although participatory mapping of fishing grounds is confined by distance to shore, the fisher-mapped sailfish and blue marlin niches provide valuable fine-scale near-shore data and overlap with several spatial and environmental features revealed by satellite tracking data. From this case study, we suggest important considerations when incorporating LEK and other ecological monitoring methods for ecological modeling and marine management. Our findings provide a social-ecological perspective of the Costa Rican billfish fishery while demonstrating the potential of fisher knowledge to help address data gaps and complement satellite tracking data in spatiotemporal modeling of economically and ecologically important billfish, with implications for data-poor fisheries worldwide.

  PublisherDOI

• The global threat of wire snare poaching: A comprehensive review of impacts and research priorities

  Biological Conservation · 2025-08-02 · 2 citations

  articleOpen access

  Wire snare poaching is an indiscriminate and pervasive form of hunting that poses a significant threat to global biodiversity. However, research synthesizing the ecological and socio-economic dimensions of snaring remains limited. To address this gap, we systematically reviewed 304 studies published between January 1977 and May 2025 to: (1) assess the global distribution of wire snaring research, (2) examine spatio-temporal trends, (3) identify core research themes, and (4) determine key knowledge gaps. We found that snaring is a global issue, occurring across Africa, Australia, Asia, North America, and Europe. Despite the global nature and increasing magnitude of snaring research over the past three decades, most research attention was in sub-Saharan Africa and Southeast Asia. Through thematic analysis, we identified five core wire snare research themes: Direct Effects, Indirect Effects, Optimized Detection, Socio-economic Dimensions, and Management Interventions. While Direct Effects (mortality and injuries) are well-documented, Indirect Effects, such as altered predator prey dynamics and behavioral shifts, remain limited, underscoring the need for innovative methodologies to better capture non-consumptive impacts of snaring. Emerging research on Optimized Detection, including machine learning, shows promise but requires further validation to overcome low snare detectability. Addressing Socio-economic Dimensions, including poverty, bushmeat demand, and community perceptions, is critical for designing effective Management Interventions. Integrated approaches combining law enforcement with community-driven conservation strategies are gaining traction. However, further research is needed to assess effectiveness and adaptability. Expanding geographic representation, advancing interdisciplinary research, and refining intervention strategies is essential to mitigating the threat of snaring and informing conservation policies globally. • Wire snaring is a global conservation threat with regionally distinct drivers • Global review identifies five core themes in wire snare poaching research • 304 studies across 53 countries and 22 subcategories of research foci • Direct effects are well studied; indirect ecological impacts remain underexplored • Thematic map reveals regional variation in dominant snaring research foci

  PublisherDOI

• Herbivore Population Differences Rival Geographic and Biophysical Variation in Structuring Ecosystem Function

  Global Change Biology · 2025-07-01 · 4 citations

  articleOpen accessSenior author

  Geographic variation in ecosystem function is often attributed to differences in climate and soil properties, with biophysical constraints assumed to dictate spatial patterns in nutrient cycling, carbon storage, and plant productivity. However, biotic interactions, particularly herbivory, also vary geographically and can generate feedbacks that influence ecosystem processes. Using a replicated three-year field experiment, we tested how population-level functional differences in a widespread arthropod herbivore mediate geographic variation in ecosystem function. Structural equation modeling revealed that herbivores exerted strong direct effects on plant biomass, soil carbon, and nitrogen mineralization, often surpassing the influence of historical conditions and geographic variation in climate. Moreover, functionally distinct herbivore populations had divergent effects on nutrient cycling and plant diversity, demonstrating that population-level differences introduce novel pathways of influence on ecosystem function. These findings challenge ecosystem models that prioritize abiotic constraints and highlight the need to incorporate consumer-driven feedbacks into ecological frameworks.

  PublisherOA PDFDOI

• Soil food web nitrogen cycling in eastern temperate forests: a tracer experiment

  2025-03-15

  preprintOpen accessSenior author

  Nitrogen cycling in temperate forests is a critical ecological process, predominantly driven by the decomposition of plant-derived organic matter by microbial activity. However, the role of soil macro-arthropods, particularly ground beetles, in mediating these processes has remained largely underexplored despite their potential to influence nutrient cycling and ecosystem dynamics. This study investigated how macro-arthropods, with a focus on ground beetles, contributed to nitrogen cycling in eastern temperate forests. Using 15N-labeled black birch leaf litter, we traced nitrogen movement through soil food webs in young and old forest stands at the Yale Myers Forest in Connecticut. Litter bags, with and without access for large invertebrates, were deployed to evaluate the contributions of macro-arthropods to litter decomposition and nitrogen cycling. We hypothesized that forest age influenced ground beetle community composition, with younger forests harboring more detritivorous beetles and older forests supporting predominantly carnivorous species with elevated 15N levels. Litter decomposition rates, soil nitrogen pools, and isotopic signatures of 15N in soil invertebrates and ground beetles were measured across three growing seasons (2022–2024). Results: We collected a total of 30,309 with the dominant groups including ground beetles, spiders, and millipedes, and detected a weak pulse of 15N in their biomass. This study provides insights into the trophic interactions and functional roles of soil macro-arthropods in forest nutrient dynamics, with implications for understanding forest ecosystem resilience and management.

  PublisherDOI

• Local Thermal Extremes Shape the Nature of Herbivore Plasticity That Controls Plant Communities

  Ecology Letters · 2025-12-01

  articleOpen access

  ABSTRACT Prevailing views hold that species' physiological plasticity may confer resilience to warming, but its importance varies across climatic gradients (e.g., latitude). Yet, along such gradients local species populations may experience fine‐scale spatially heterogenous variation in extreme temperatures and other ecological stressors. We show that at four Cool (mean diel maximum 29.83°C) and four Warm (mean diel maximum 31.51°C) sites, interspersed as a spatial mosaic throughout a 26,200 km 2 area, local herbivore populations responded differently to stress from experimental warming (ambient, warmed) and predation (presence, absence). Cool and Warm site herbivore populations utilised different combinations of behavioural and physiological plasticity to cope with the dual stressors that were contingent on local temperature extremes. These unique plastic responses had divergent cascading effects on the plant community. Our results suggest that increased attention to local population variation can enhance the ability to predict the fate of natural communities under environmental change.

  PublisherOA PDFDOI

• A trait‐based framework for adaptive phenotypic plasticity under global change

  Oikos · 2025-09-01 · 3 citations

  article

  Phenotypic plasticity is often regarded as a key mechanism for coping with environmental change, yet its adaptive potential remains uncertain in part because of inconsistencies in how environmental stressors are defined and studied, and the traits that are studied. We propose a framework that partitions global change into four distinct dimensions: mean change, variability, stochasticity, and episodic events, each of which presents unique challenges for organisms. A central determinant of plasticity's adaptive value is predictability, yet existing studies inconsistently quantify it, conflating structured environmental variation with stochasticity. We introduce standardized approaches to measuring predictability and cue reliability, ensuring that plastic responses are assessed in ecologically meaningful contexts. We then present a multiple‐trait‐based framework for evaluating the likelihood of plastic trait deployment across increasing magnitudes of global change dimensions. This framework serves as a heuristic model to guide research priorities, identify key knowledge gaps, and generate testable hypotheses about the conditions under which plasticity may contribute to persistence in the face of global change. Through a case study of Daphnia pulex , we demonstrate how the framework can be used to identify key new research approaches and identify empirical data needed to reveal and explain emergent patterns across trait types and global change conditions. By refining predictability metrics and experimental approaches, this framework advances efforts to determine when and where plasticity can buffer populations from global change, offering a foundation for future research and conservation planning.

  PublisherDOI

• Large herbivore functional guilds and soil carbon storage in a semi-arid southern African landscape

  Research Square · 2025-03-20

  preprintOpen accessSenior author
  PublisherOA PDFDOI

Recent grants

• Complexity and Stability of an Old-field Ecosystem: The Role of Asymmetrical Interaction Strengths and Food Web Toplology

  NSF · $473k · 2008–2013

• Predator Identity and Trophic Control of Biodiversity and Ecosystem Function

  NSF · $481k · 2005–2009

• The macrophysiology of food chain dynamics

  NSF · $523k · 2014–2019

• DISSERTATION RESEARCH: How will climate change affect trophic interactions?

  NSF · $13k · 2009–2011

Frequent coauthors

• Joel S. Brown

  Moffitt Cancer Center

  14 shared

• Burt P. Kotler

  Ben-Gurion University of the Negev

  13 shared

• Mark A. Bradford

  Yale University

  13 shared

• Robert W. Buchkowski

  Western University

  13 shared

• Andrew P. Beckerman

  University of Sheffield

  12 shared

• Dror Hawlena

  Hebrew University of Jerusalem

  12 shared

• Shawn Leroux

  Memorial University of Newfoundland

  11 shared

• Michael R. Heithaus

  Florida International University

  10 shared

Education

• PhD

  University of Michigan

  1989