Conférence

L'île Maurice depuisle dernier âge glaciaire

Reconstitution des paléo-environnements et paléo-climats à l'île Maurice

Présentation des résultats duprogramme de recherche

“Mauritius since the last ice age”

12 Mars 2014

Salle T12Campus universitaire sud

Le Tampon

Présentations orales, postersArticles scientifiques et de vulgarisation

Coordination du projet (Amsterdam)MSc. Erik de Boer – E.J.deBoer@uva .nl Dr. Kenneth Rijsdijk – K.F.Rijsdijk@uva.nl Pr. em. dr. Henry Hooghiemstra – Hooghiemstra@uva.nl

Organisation de la conférence (Réunion)Pr. Dominique StrasbergDr. Olivier Flores

Salle T12

Programme

13.00 Accueil / ouverture13.15 – 13.45 Dominique Strasberg / Olivier FloresSome facts about the natural history of La Réunion

Session 1. Island biogeography and paleoecologyLeader: Erik de Boer

13.45 – 14.10 Henry Hooghiemstra (1)14.10 – 14.35 Henry Hooghiemstra (2)14.35 – 15.00 Kenneth Rijsdijk (3)

15.00 – 15.15 Discussion

15.15 – 15.30 Pause

Session 2. Natural history of MauritiusLeader: Henry Hooghiemstra

15.30 – 15.55 Erik de Boer (4)15.55 – 16.20 Erik de Boer (5)16.20 – 16.45 Kenneth Rijsdijk (6)

16.45 – 17.00 Discussion

17.00 – 18.00 Réception

Résumé des présentations

SESSION 1. ISLAND BIOGEOGRAPHY AND PALEOECOLOGY

(1) An introduction to paleo-ecology & climate changePr. Henry Hooghiemstra

In this talk paleo-ecological methods are briefly explained. Europe and Saharan Africa are used as an example to show the dramatic changes from glacial to interglacial conditions. A framework is shown to understand current and future environmental and climate change. Finally, questions are addressed such as ‘what were past responses of tropical ecosystems to the magnitude and rates of climate change?

(2) Tropical forest dynamics: oceanic islands and islands-in-the-skyPr. Henry Hooghiemstra

In this talk the assumption is addressed that islands offer a stable environment for flora and fauna. Environmental dynamics since the last ice age from Indian Ocean islands are compared with Andean mountain tops. Significant differences in operating mechanisms are shown. Common characteristics between gene-pools of islands may explain high levels of resilience allowing insular biomes to shrink dramatically without significant loss of biodiversity. Finally, questions are addressed such as ‘were these changes similar to those predicted/projected for the next century?’

(3) Does sea level change affects biodiversity of volcanic islands?Dr. Kenneth F. Rijsdijk & BioIslands Group

As a result of Pleistocene sea level changes, volcanic islands change in size and archipelagos change in configurations.

During sea level falls islands increase and guyottes may emerge that act as new stepping stones resulting in an increase of biogeographic connectivity; whereas during sea level rise islands shrink, the distance to continents increases and connectivity decreases. We developed an R-algorithm (pBIG) that is able to model island surface change as a consequence of sea level change. We use metrics that record size and distance change per island in linear mixed models to assess whether sea level change can be used as predictors for species richness of volcanic islands.

SESSION 2. NATURAL HISTORY OF MAURITIUS

(4) The paleoecology of Mauritius: Long-term ecology of a degraded islandErik J. de Boer MSc, Pr. Henry Hooghiemstra, Dr. F.B. Vincent Florens, Drs Cláudia Baider

Four centuries of human occupation has left Mauritius with <5% of its original vegetation cover. Consequently, little is known about floral and faunal distribution patterns and long-term ecological processes of this oceanic island. By using paleoecological techniques we record the impact of environmental change, climate extremes, and human disturbance on the island’s unique flora and fauna. Our records show many plant species, notably palms, which went extinct after colonization but before botanical surveys recorded their native status. In order to preserve species and their ecosystems, it is vital to know the driving mechanisms of deep-time ecological change. Paleoecological reconstructions are therefore essential to target understanding of the main ecosystem processes with substantial implications for nature conservation.

(5) Holocene climate variability from MauritiusErik J. de Boer MSc, Pr. Henry Hooghiemstra, Dr. Rik Tjallingii, Dr. Maritza I. Vélez, Dr. Perry G.B. de Louw, Dr. Kenneth F. Rijsdijk

Upland ecosystems (~500 m asl) show that climate changes have secondary effects on montane forest composition, whereas edaphic conditions and interspecific competition constitute a heterogeneous pattern of species associations. In contrast, ecosystems below 200 m asl are much more vulnerable to climate changes due to lower and seasonal precipitation patterns. This sensitivity was used to compare precipitation variability in Mauritius with Indian-Asian and Indonesian-Australian monsoon records. We demonstrate that Mauritian climate is driven by northern hemisphere dynamics on millennial timescales and is affected by decadal droughts and wet events following Indian Ocean Dipole configurations and variations in the El Niño–Southern Oscillation (ENSO) system.

(6) Exploring a fossil Lagerstätten on a hotspot island: Assessing its conservation potential and interdisciplinary research approachDr. Kenneth F. Rijsdijk, Dr. Perry G.B. de Louw, Pr. Henry Hooghiemstra, Erik J. De Boer MSc

We discuss the conditions that led to the formation and conservation of a fossil Lagerstätten of Mauritius, and we compare the onsite (palaeo and actuo) environmental conditions with similar sites on other volcanic islands. We highlight the importance of integrating disciplines including geology, geomorphology geohydrology, taphonomy, geo-biochemistry, palaeo-ecology and actuo-ecology. We discuss the fieldwork logistics involved and the equipment used.