Mauritius since the last ice age: paleoecology and climate of an oceanic island

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.
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.
Driest conditions are recorded 4200 years ago during the subtropical-scale '4.2 ka megadrought'. This climatic extreme caused crashes in vertebrate populations in Mauritius. No extinctions were recorded before colonization, but 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.