To explain the current biodiversity of the islands it is necessary to look at the distant past
Portuguese islands included in the analysis which considers that it is not enough to look at the last 20 thousand years and that it is necessary to go back to 800 thousand.
A study involving more than 50 volcanic islands, including the Azores and Madeira, concludes that biodiversity can only be understood if one looks at the variation in sea level over the last 800 thousand years.
Published in the journal Global Ecology and Biogeography, the work “contradicts most studies in the area, which consider only extreme sea levels recorded in the recent past, about 20,000 years ago”, explains the communiqué from the Centre for Ecology, Evolution and Environmental Change.
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The fluctuation of sea level has changed over thousands of years between very low, during cold periods, and very high, during warm periods, influencing “the wealth and geographical distribution of the species that currently inhabit these islands”. “Today the sea level is relatively high, but for most of the last millions of years the climate has been colder and therefore the sea level was lower than it is today”, the statement explains.
While taking into account these changes, much of the research done on biodiversity has focused on “current sea levels, or considered a specific and short-lived period of the Earth’s recent past as determining current patterns of biodiversity: the Last Glacial Maximum, an exceptional period that took place some 20,000 years ago when ice sheets were at their widest and therefore sea levels were extremely low”.
The team, led by Sietze Norder of the Centre for Ecology, Evolution and Environmental Change of the Faculty of Sciences of the University of Lisbon, worked with the Biodiversity Group of the University of the Azores and looked at data on the richness of species of land snails and flowering plants from 53 volcanic oceanic islands of 12 archipelagos around the world, including the Azores, Madeira, Galapagos, Canaries and Hawaii.
The combination of the information collected with “data on the occurrence of thousands of species has allowed researchers to explore the role of past environmental dynamics in setting current biodiversity standards”.
“Volcanic oceanic islands are excellent places to study the role of long-term sea level fluctuations in shaping biodiversity patterns, as they are inhabited by many endemic species that do not occur anywhere else in the world,” notes Sietze Norder. “Often these endemic species have evolved on an island over large time scales and have therefore experienced several cycles of sea level rise and fall”.