A research team on Tenerife takes sediment cores containing pollen, which revealed the effects of more recent human colonization of the island. Photo by José María Fernández Palacios/University of Bayreuth
April 30 (UPI) -- An international team of researchers found that humans have significantly altered biodiversity on colonized islands in the past 1,500 years, according to a study published Friday in the journal Science.
By analyzing 27 fossil pollen sequences encompassing 5,000 years from islands across the world, scientists quantified the rates of change in vegetation composition before and after human arrival.
According to the analysis, there were faster rates of turnover on islands colonized in the past 1,500 years than for those colonized earlier.
Professor Dr. Manuel Steinbauer of the University of Bayreuth and Dr. Sandra Naogue of the University of Southampton extracted, dated and identified pollen from wind-pollinated plants deposited in the sediment of lakes and bogs.
The islands chosen for the study were never connected to the mainland, researchers said.
"For each of the 27 islands, our study shows how vegetation composition has changed over the last 5,000 years. Humans' colonization of the previously undisturbed islands falls within this period. We can therefore trace how natural systems change as a result of human arrival," said study co-author Steinbauer.
"This transformation from a natural to a human-dominated system can only be observed on islands. On continents, humans have been extensively changing ecological systems for a very long time. What a natural ecosystem would look like here, we can often no longer tell," Steinbauer said.
On 24 of the 27 islands studied, the arrival of humans marked a significant change in vegetation, especially on islands colonized in the past 1,500 years.
For those colonized earlier, the turnover was less pronounced.
The researchers attribute this difference with an increase in agricultural technology and its associated effects on biodiversity.
"The results of the study highlight the extensive changes we humans are causing in ecological systems. The change in pollen composition in our study mainly reflects human land use over millennia," Steinbauer said.
"With the beginning of the industrial age, human-induced transformation of ecological systems has accelerated even further. Adding to this, ecological systems are now additionally affected by human-induced climate change," he said.