Research Portfolio

Umer Gurchani

I study how different forms of interaction among individuals and species give rise to collective behavior in complex systems. I am particularly interested in how much knowledge of these relationships is required to predict future system dynamics and support effective policy decisions. My work spans political communication and biodiversity conservation.

Network analysis Computational modeling Uncertainty-aware conservation

Contact: muhammad.umer.gurchani@ens.psl.eu

Portrait of Umer Gurchani

About me

I am a postdoctoral researcher at the Institut Jean Nicod (ENS–PSL). I study systems whose behaviour depends on relational structure — who is connected to whom — and on how much of that structure we can actually observe.

My doctoral work was on political networks: homophily, retweet hierarchies, and fragmentation in the French Twitter network. My current work is in ecology and conservation: food webs, biodiversity metrics, and conservation decisions. The domain changed; the questions did not.

Profile

RolePostdoctoral researcher
AffiliationInstitut Jean Nicod, ENS–PSL
DomainsPolitical networks → ecological networks
Published inScientific Reports, PLOS ONE, Social Media + Society

Questions I'm interested in

  • When species interactions are only partially known, how should conservation decisions be made — and how much should we invest in learning the structure before acting?
  • Can early, precautionary conservation ever perform worse than waiting, once structural uncertainty about ecological dependence is taken into account?
  • How should conservation priorities balance phylogenetic diversity (evolutionary history) against functional diversity (ecological roles)?
  • How does that balance shift as interaction knowledge accumulates over time?
  • More generally: how does network structure constrain what can be inferred about a system, and how should decisions adapt under partial observability?

Hypotheses I'm pursuing

  • Under high structural uncertainty, the value of precautionary conservation can invert — acting too soon may do worse than delaying until key dependencies are understood.
  • Ecological knowledge can be treated as a conservation asset in its own right, and investing in it helps resolve trade-offs between present and future biodiversity.
  • The optimal weighting of phylogenetic versus functional diversity is not fixed; it moves systematically as interaction knowledge grows.
  • Network structure carries enough signal to support inference and prediction even when the full system is never directly observed.

Methods I'm using

  • Food-web and predator–prey network modeling
  • Sequential decision-making in partially observable environments
  • Hindsight-based and counterfactual simulation, comparing adaptive against fixed decision rules
  • Inverse reinforcement learning
  • Empirical analysis of a 148-year Northeast Atlantic fish stomach-content dataset
  • Simulated food webs; phylogenetic and functional diversity metrics
  • Network analysis and graph-derived inference, carried over from earlier political-network research

Current projects

Structural uncertainty & precaution

Whether early, precautionary protection helps or backfires when the ecological dependencies at stake are barely understood.

Knowledge as a conservation asset

Whether investing in ecological knowledge can resolve trade-offs between protecting biodiversity now and in the future.

Related publications

Too Soon to Save (bioRxiv, 2026) and Treating Knowledge as a Conservation Asset (Scientific Reports, 2026) — listed under Publications.

Ecological networks Food webs Conservation planning Partial observability Phylogenetic diversity Functional diversity Adaptive decision-making Value of knowledge

PhD thesis

Political Homophily and the Role of Retweeters in the French Twitter Network

Université de Montpellier, 2021

In my doctoral work, I examined how political communities form and diverge inside the French Twitter network, and what that divergence implies for the idea of a shared public sphere. The thesis began with a simple but important question: does participation in political Twitter push all communities toward isolation, or is the effect uneven across ideological camps?

Questions I asked

  • How does political homophily evolve over time in the French Twitter network?
  • Which communities become more isolated, and which remain more embedded in the wider political network?
  • What does the behavior of retweeters reveal about political mediation and hierarchy?

Hypotheses I tested

  • Homophily would not grow uniformly across all political communities.
  • Some communities, especially at the nationalist or far-right edge, would diverge more strongly from the broader network.
  • Political retweeting would often operate less as horizontal diffusion and more as a top-down mechanism of ideological reinforcement.

Methods I used

Graph construction

I separated the French Twitter political space from the broader global network and modeled it as a graph of users and interactions.

Community detection

I identified political clusters and tracked how their structural relationships changed over time.

Focused crawl design

I developed and used a focused back-and-forth crawl strategy to gather network-level data without needing a full platform graph.

Feature extraction & inference

I used communities as graph-derived features for predicting political affiliations on a continuous scale.

Retweet analysis

I analyzed retweet behavior to determine whether it bridged elites and masses or reinforced hierarchical communication.

Interpretive framing

I connected the empirical findings to questions about the public sphere, mediated hierarchy, and refeudalization.

What the thesis found

The central result was that homophily did not intensify equally across all groups. The strongest long-term divergence appeared in communities associated with more extreme nationalist politics. In parallel, the study of retweeting suggested that, at least in some communities, retweets were used less for open circulation and more for top-down ideological reinforcement. Together, these findings pointed toward a differentiated, asymmetric fragmentation of the political public online.

Interactive demo — The Public Sphere

Built directly on this corpus: ask one question and hear the three political camps from the 2022 French election — Left / Insoumis, Centre / Renaissance, and Right / Nationalist — answer in their own voice, each grounded in real tweets from that community. Then click a voice to keep talking to it.

▶ Open the interactive demo

Publications

2026

Treating Knowledge as a Conservation Asset to Resolve Present–Future Biodiversity Trade-offs

MU Gurchani, J Montoya, S Bourgeois-Gironde · Scientific Reports, 2026

Too Soon to Save: Structural Uncertainty Inverts the Value of Precautionary Conservation Action

MU Gurchani, JM Montoya, S Bourgeois-Gironde · bioRxiv, 2026

View preprint

2025

Six Key Policy Recommendations to Advocate for Marine Conservation that Matches the Ocean's Dynamism

OJ Esteban-Cantillo, A Abreu, S Bourgeois-Gironde, E Wanek, et al. · npj Ocean Sustainability 4(1), 50, 2025

Three Forms of Temporal Disorientation: A Thematic Analysis of Subjective Reports about Covid-19 Restriction Periods

B Perroy, PF Velasco, U Gurchani, R Casati · PLOS ONE 20(6), e0324476, 2025

View publication

2024

Right-Wing Twitter Users in France Exhibit Growing Homophily Compared With Left and Center Users

MU Gurchani · Social Media + Society 10(1), 2024

View publication

Social and Temporal Disorientation during the Covid-19 Pandemic: An Analysis of 3306 Responses to a Quantitative Questionnaire

P Fernandez Velasco, U Gurchani, R Casati · British Journal of Psychology 115(4), 577–598, 2024

Disorientation and Time Distortions during the Metro Commute

B Perroy, U Gurchani, R Casati · Quarterly Journal of Experimental Psychology 77(9), 1911–1922, 2024

Territorializing the Sea: Equilibrium, Seaward Projection, and Seaward Exposure of World Countries

R Casati, MU Gurchani · GNOSIS, 2024

2023

Lost in Pandemic Time: A Phenomenological Analysis of Temporal Disorientation during the Covid-19 Crisis

PF Velasco, B Perroy, U Gurchani, R Casati · Phenomenology and the Cognitive Sciences 22(5), 1121–1144, 2023

2022

Experiencing a Slow Passage of Time was an Indicator of Social and Temporal Disorientation during the Covid-19 Pandemic

P Fernandez Velasco, B Perroy, U Gurchani, R Casati · Scientific Reports 12(1), 22338, 2022

Development and Validation of a Quantitative Instrument for Measuring Temporal and Social Disorientation in the Covid-19 Crisis

P Fernandez Velasco, U Gurchani, B Perroy, T Pelletreau-Duris, R Casati · PLoS ONE 17(11), e0264604, 2022

2021

Political Homophily and the Role of Retweeters in the French Twitter Network

MU Gurchani · Doctoral thesis, Université de Montpellier, 2021

View thesis

Crawling Political Communities in Twitter and Extracting Political Affiliations

MU Gurchani · arXiv, 2021

View preprint