Portuguese researcher Maria Dornelas, from the Scottish University of St. Andrews, told Lusa news agency that the study reveals that "the change in species composition is very rapid" and that "almost a third of species" in a given ecosystem is replaced by others within a decade.

Although global numbers of species numbers decline, this is not necessarily reflected at the local level because "they are different scales, where there are enough species and locations for species redistribution."

"The big question is 'Why?'" said the researcher, who hopes the study will serve as a basis and encourage further research into why.

"For now, we only have hypotheses. The 'usual culprits' such as global climate change or ecosystem exploitation" are some that can be explored, she said.

As for the greater volatility of marine ecosystems, particularly in tropical climates, at the outset "species transit is easier, there are fewer borders".

Temperature change is a factor to which marine species "tend to be more sensitive" because they do not control their internal temperature and there are no micro refuges. A terrestrial animal in the sun can look for a shadow," she said.

For this study, an international team of scientists led by St. Andrews, the German Centre for Integrated Biodiversity Research and the University of Halle-Wittenberg looked at data collected over the last century, especially the last 40-50 years, in 50,000 locations around the world, with "the collective work of hundreds of researchers".

Maria Dornelas noted that catastrophic cases for biodiversity such as the Amazonian wildfires focus a lot of attention, but around the world there are recovering ecosystems, losing species that are replaced, while those leaving one ecosystem may thrive in another zone.