FORCES aims towards establishing an evidence-based nature-based solutions (NbS) framework by implementing innovative forest-based solutions. FORCES seeks to develop ecosystem-based adaptation actions that simultaneously preserve high levels of biodiversity, ensure sustaining natural capital and the flow of ecosystem services while protecting communities’ livelihoods and contributing to climate change mitigation. Considering that combined actions on climate, biodiversity and societal challenges cannot efficiently be achieved without multiple actors’ engagement in local actions, FORCES’s strategy is to develop local innovation actions, provide methods and tools to support their extended use and assess their potential global impacts. Thus, FORCES will: i) conduce trans-disciplinary research based on new developments in environmental and social sciences underpinned by stakeholders’ expertise; ii) design, implement and assess local innovation actions based on stakeholders’ engagement; iii) address cross-scale issues from local actions to global impacts; iv) elaborate a tool box of science-based methodologies and standards to promote the use of nature-based solutions that contribute to achieving specific UN sustainable development goals, combining SDG13 “Climate action” and SDG15 “Life on land”, and address societal challenges. FORCES will develop research and innovation actions in various types of forest socio-ecosystems, aiming to generalize forest-based solutions, and will interact with similar projects on other ecosystems through a clustering approach as mentioned in the call. Forests are appropriate for this research and innovation action because: (1) forests harbor an important terrestrial biodiversity and are particularly vulnerable to climate change due to cumulative effects of annual climate on trees, (2) forests are social-ecological systems providing multiple ecosystem services and contributing to people welfare, they are a lever for C-sequestration and substitution, (3) in the context of global change and multiple uncertainties, the emergence of a new paradigm in forest management offers opportunities to innovate, (4) forests are at the cross-road of multiple EU policies but biodiversity and climate objectives are not yet considered jointly in forest policies and strategies. NbS will be designed and assessed in six types of forest systems in Europe and the CELAC. These Innovation Action Areas will be supported by associated Research Sites for data acquisition and model calibration. Multiple time frames will be considered to account for uncertainties in global change scenarios (2035, 2050, 2100).

Global changes are causing deep modifications of ecosystems and their functioning, leading directly to species extinctions and functional shifts and indirectly to alterations of the ecosystem services they deliver. In the last decades, modelling the impact of global changes on biodiversity and ecosystem services has been an active area of research with strong expectations from conservation agencies, national and international programs, as well as biodiversity managers and conservation associations. However, most existing models still ignore basic mechanisms including biotic and abiotic interactions. Biodiversity is not merely the sum of species, but is also the result of interacting species that form assemblages, at various spatial and temporal resolutions, with different functional characteristics and evolutionary histories. Models ignoring these mechanisms are prone to provide erroneous predictions of how global changes will impact biodiversity or ecosystem services. Addressing these gaps requires a multi-scale approach that spans different fields of ecology and statistics with input from stakeholders and policy makers in order to ensure that the results from the theoretical research can realistically be implemented. Recently, tremendous progress has been made in extending species distribution models to Joint Species Distribution Models (JSDMs). These models predict species distributions based on environmental and spatial variables, but they also allow species to share information on their responses. JSDMs hierarchically model biodiversity from the species level to the functional group level, taking into account potential dependencies between species - for example based on their phylogenetic distances. JSDMSs expand and unify classical methods used in community ecology or in conservation biology and are currently used to model synergies and tradeoffs between ecosystem services. However, as promising as they are, the large and extensive use of JSDMs is still hampered by several limitations both ecologically and statistically that GAMBAS proposes to address. First, there is a lack of a clear classification and nomenclature associated with the ecological and statistical assumptions on which they are based. Second, JSDMs provide estimates of correlation between species. But do these correlations indicate true interactions between species? Third, mathematical developments are required to elucidate links between statistical and ecological assumptions or to insure a more robust and efficient use. Finally, JSDMs, which currently remain an academic research topic, have rarely been confronted to practical problems such as the identification of conservation zones. In GAMBAS, we will focus on the analysis of five datasets, which will both be an inspiration and will constitute the first concrete case studies for our developments. GAMBAS gathers a collective comprised of quantitative ecologists and mathematicians with aspirations in ecology. These investigators will be supported by an advisory committee composed of representatives of the French government and civil societies. Together, they have set the goal of expanding JSDMs and to promote their use in community ecology, biogeography, and conservation ecology.

The project Trajectories of Social-Ecological Systems in Latin American Watersheds: Facing Complexity and Vulnerability in the context of Climate Change (TRASSE) will aim at operationalising the framework of Social-Ecological Systems in rural-urban watersheds of Mexico, Colombia and France. Beyond pure descriptive operationalization the project will advance on a theory of change for the sustainability of complex human-nature systems. Such a theory of change will be developed through a retrospective historical and ecological analysis of past trajectories in combination with spatiotemporal prospective modelling.

Tropical forests are currently experiencing huge pressures from global changes. If tropical deforestation has been rightly the focus of much attention these last decades, forest degradation and its consequences in the tropics has been much less studied and quantified. Yet, forest degradation is pervasive throughout the tropics and leads to a significant loss of ecosystem services. Hence, a major issue is the reversibility of degradation. In many cases, natural successional processes are expected to bring back the system to a state similar to the initial one. However, in some cases, the system may have trespassed a threshold and lost its ability to follow such a classical successional pathway; it may remain in a so-called blocked succession or in an alternative degraded stable state. The Marantaceae forests from Central Africa likely correspond to such stable degraded systems. They cover very large areas in Central Africa and have a very low density of trees with a dense understory composed of giant herbs. The few studies on Marantaceae forests suggest that their large patches (up to 2000 km2) are likely to have originated from old disturbances (>1000 years ago) and have been maintained over long periods through positive feedback mechanisms, e.g. inhibition of tree regeneration by giant herbs. Observations also suggest that current human disturbances, such as logging activities, as well as climate anomalies, contribute to the rapid expansion of these degraded forests, which could have considerable consequences for local populations. In this project, we will study the mechanisms by which Marantaceae forests may originate and be maintained at different spatial and temporal scales. We will combine observations at the local and regional scales (among which historical data) and parsimonious theoretical models to study the long-term dynamics of Marantaceae forests, the conditions under which stability is expected and the mechanisms by which giant herbs monopolize space and may outcompete trees or restrain their development. The project will be structured in four complementary main work packages (WP): WP0 will be dedicated to synthesize previous studies conducted on Marantaceae forests, of which many were reported as grey literature; WP1 will aim at investigating the main ecological mechanisms underlying the dynamics of Marantaceae forests; WP2 will aim at depicting the contemporary ( 500 yrs) spatio-temporal dynamics of Marantaceae forests based on remote sensing data and historical ecology approaches; and WP3 will consist in devising mathematical models to understand the conditions of a post-disturbance stability of Marantaceae forests and the relative importance of the drivers of this stability. WP3 will thus bridge the scale gap between the local ecological mechanisms (WP1) and the broad scale spatio-temporal dynamics (WP2) of Marantaceae forests. Overall, our project will generate important knowledge on the dynamics of a system that constitutes an important part of the tropical African wet forests and ofglobal concern regarding biodiversity and carbon sequestration in the second largest tropical forest area in the world. It will also contribute to the increased awareness that the dynamics of ecosystems is not systematically reversible and that external forcings may make them shift to alternative stable states. The ultimate goal of the project is to anticipate the potential consequences of global changes on the dynamics of Marantaceae forests and to provide recommendations for forest conservation and management.