Following his master's thesis on "the problem of surplus population" in Malthus and Marx, his doctorate under the direction of Pierre Charbonnier aims to extend this historical work to a critique of neo-Malthusianism which, since the second half of the 20th century, has provided an analysis of the ecological crisis in demographic terms.

Many authors such as Paul Ehrlich or Garret Hardin have pronounced the neo-Malthusian verdict of catastrophism: we - but especially the Others in the countries of the South - are "too many", the carrying capacity of the Earth's ecosystems will soon be exhausted, causing epidemics, famines and conflicts in a context of resource scarcity.

Starting from a critique of neo-Malthusian environmentalism in particular, he looks more generally at the environmental history of (natalist or anti-natalist) population doctrines since the pre-Malthusians. By questioning the reductive naturalism of concepts such as "optimum population" or "carrying capacity", he aims to critically reflect on the criteria, both natural (planetary limits) and normative (the type of social organization), that permit to establish the concept of "overpopulation". How can we envisage the sustainable reproduction of the collective life of a world population of 10 billion in 2050, while moving beyond intensive agriculture based on fossil infrastructure and synthetic fertilizers that disrupt the nitrogen cycle? Would the city allow for sustainable urbanism through the efficient management of common resources in a post-fossil fuel economy?

In order to propose a critical theory of population that is not only a quantified perspective of demography following the expression of "world population" but that articulates within it different qualitative determinants of population such as demographic evolution in relation to its ecological environment and socio-economic inequalities, he puts forward the heuristic hypothesis of an actualization of the Marxian theory of "relative surplus population". By questioning the conceptual couple population-subsistances, he intends to identify the population surplus as a socio-economic surplus determined by the scarcity of employment and embodied by the "relative surplus working population, surplus to the average needs of capital valorization and therefore superfluous" (Marx).

With the help of the political economy of relative surplus population and in contrast to the catastrophic visions of a "rush to Europe" from the African continent, he is interested in environmental inequalities in the countries of the South and in the horizon of climate justice. How does the ecological crisis, through rising waters, air and soil pollution, threaten the "relative surplus population" of the poor and excluded in the South? What are the effects of the destruction of the natural balance of ecosystems on the socio-economic imbalance between supply and demand of labor in the world economy? How is population growth in non-developing regions likely to increase pressure on labor markets, reinforcing exclusion? These two demo-ecological factors of "dispossession" are likely to favor important exoduses increasing the number of climate refugees. He is therefore interested in how the social and climatic vulnerability that places this population on the front line in the struggle for survival and for a just and sustainable life in the Anthropocene era is likely to be transformed into political power.