" The future of tropical ecosystems – new insights and innovative methods "

Plenary sessions

Keynotes talks

The botanical consequences of megafauna extinctions

Tuesday June 7 – 9:00 – 9:45 – Duplex Agropolis International Amphi L. Malassis / Cirad Amphi J.Alliot

Many tropical plants have evolved traits in response to interactions with megafaunal animals, such as large, ‘megafaunal’ fruits or defence traits (e.g., spines). However, two major global extinction events in Earth’s history impacted terrestrial megafauna dramatically: The Cretaceous–Paleogene extinction of the non-avian dinosaurs, and the much more recent Late Pleistocene and Holocene extinctions of many megafaunal mammals, reptiles, and large birds. The eco-evolutionary consequences of these extinction events for plants that were pre-adapted to interact with megafauna remain poorly explored. In this talk, I will apply comparative methods and phylogenetic modelling to show that the 25-million-year gap of megaherbivores after the non-avian dinosaur extinction and before the evolution of megaherbivorous mammals in the Late Eocene, was characterized by speciation slowdowns, decreased evolution of defence traits, and increased evolution of megafaunal fruits in palms (Arecaceae). Then, using a novel database of >1500 present-day megafruit plant species and >10000 seed-dispersal records, I will show that ‘true’ anachronistic megafruit species (without any dispersal record) suffer from dispersal limitation, small geographical range sizes, and high extinction risk compared with megafruit species still dispersed today by large ungulates, apes, rodents, and humans. I will discuss how the disruption of mutualistic and antagonistic interactions affects plant survival and persistence in defaunated landscapes.

A ‘seabird’ eyeview on tropical marine ecology in the Anthropocene.
Pr Guilherme Tavares Nunes
Dr Sophie Bertrand

Tuesday June 7 – 13:30 – 14:15 – Duplex AI/CiradDuplex Agropolis International Amphi L. Malassis / Cirad Amphi J.Alliot

The oceans in general, and in tropical latitudes in particular, are now at the heart of climatic, ecological, economic and political issues. In terms of science, they are therefore frontier objects for which observation, understanding and forecasting call on a wide range of techniques and knowledge. Focusing here on the biological seabird model, we will illustrate how advances in instrumentation and modelling are revolutionizing nowadays the ways of defining niches and critical habitats in space and time, assessing the current impacts of human activities at sea and unlocking the perspectives for imaginating alternative ocean governance under global change.

The impact of lianas on the carbon cycle and demography of tropical forests: insights from vegetation models, water isotopes and terrestrial laser scanning
Pr Hans Verbeeck

Wednesday June 8 – 9:00 – 9:45 – Duplex Agropolis International Amphi L. Malassis / Cirad Amphi J.Alliot

Lianas are an important component of tropical forests. They compete strongly with trees for both above- and below-ground resources. Their indirect impact on the carbon balance, due to their influence on tree community dynamics, is far larger than their direct contribution to the forest biomass. Currently tropical forests are experiencing large-scale structural changes, including an increase in liana abundance and biomass. This may eventually reduce the projected carbon sink of tropical forests. However, lianas might also cool the forests due to their impact on the forest energy balance. Despite their crucial role, no single terrestrial ecosystem model had included lianas until recently. Moreover, key data on aboveground and belowground competition between lianas and trees was lacking to develop such models. In this talk I will give an overview of the work we did the past five years to close this knowledge gap.
In the first place we collected new data to study liana-tree competition. Based on innovative stable water isotope monitoring we found that lianas have a very shallow root system in wet tropical forest, contrasting the long standing ‘deep-root hypothesis’ for lianas. Secondly, we studied the impact of liana load on tree allometry using terrestrial laser scanning. Based on these studies and existing data we started to develop the first vegetation models that account for lianas.
We tested the models against data of multiple field sites in French Guiana and Panama. This analysis allowed us for the first time to study the impact of lianas on the different components of the forest carbon and energy cycle in an integrated way. Our results confirm that lianas reduce forest productivity and biomass significantly. The models also allow us to start exploring ecological questions and underlying mechanisms. We therefore explored the ED2 model by a sensitivity analysis to study the role of belowground versus aboveground competition and evaluated the impact of liana proliferation on the forest albedo using radiative transfer modelling.

Drivers and impacts of deforestation and forest degradation in Amazonia
Dr Erika Berenguer

Wednesday June 8 – 13:30 – 14:15 – Duplex Agropolis International Amphi L. Malassis / Cirad Amphi J.Alliot

Currently, 17% of the Amazon has been deforested, while a further 17% has been degraded. However, neither deforestation nor degradation are evenly spread across the basin, being most concentrated in Brazil. Identifying the different drivers of deforestation and forest degradation is crucial to develop a better understanding of their impacts and their possible interactions. Impacts are varied and not only ecological, but also social. In this talk, I will review the main drivers of deforestation and forest degradation across Amazonia and their associated impacts. I will also discuss the different pathways of forest recovery after anthropogenic disturbances and whether the Amazon is past a point of no return.

Extraordinary forest disturbances in South America: landscape fires

Thursday June 9 – 9:00 – 9:45 – Duplex Agropolis International Amphi L. Malassis / Cirad Amphi J.Alliot

Tropical forests represent nearly half of the world’s forested area. Unfortunately, whilst we have a detailed understanding of one of the dominant processes of human-driven disruption of tropical forests, i.e., deforestation, degradation in forest-dominated areas of South America is largely understudied. Recent estimates of forest degradation point out that changes in forest structure and biomass reduction together represent a substantial part (~69%) of the total carbon lost in tropical regions. Although both, edge-effects associated with deforestation-driven fragmentation and tree logging, are important contributors to forest degradation, fire has a prevalent role over large geographical areas. Climate change and land-use change are projected to make fires even more frequent and intense. Understanding the different types of fires and its contribution to large-scale forest degradation becomes of primary importance. Our results provide evidence of the effects of 20 years of a large-scale fire-driven degradation in South America forests. Fire-driven degradation impacts mid-term forest functioning, and it acts as a recovery retarder. We will discuss how the recovery of fire disturbed forests is also highly sensitive to other disturbances. Finally, we will argue that a radical change is needed in the way landscapes are managed and the urgent need of governments to shift towards prevention and preparedness to the increasing occurrence of landscape fires, largely exacerbated by climate change.

How forest management for timber production can be a tool for the conservation of tropical forests?
Dr Plinio SIST

Thursday June 9 – 13:30 – 14:15 – Duplex Agropolis International Amphi L. Malassis / Cirad Amphi J.Alliot

The monitoring of tropical rainforest dynamics for several decades within permanent plots suggests that the rules of selective logging in tropical rainforests (cutting intensity and duration of rotations) currently set by most forestry legislation cannot ensure a sustainable timber yield on a long term basis. The present conditions, which are supposed to promote sustainable management, are largely questioned by science. It is therefore urgent to think about new management rules and practices and to anticipate new sources of timber because natural forests alone will not be able to supply tomorrow’s timber demand. The very principles of tropical silviculture still in force today as well as the place of natural tropical production forests in a context of climate change must deeply reviewed. Restoration programs are an opportunity to think about a planned forestry transition adapted to this paradigm shift, which is as necessary as it is vital for the future of tropical rainforests.