Featured Research

from universities, journals, and other organizations

Is Extinction Or Diversity On The Rise? Study Of Islands Reveals Surprising Results

Date:
August 27, 2008
Source:
University of California, Santa Barbara
Summary:
It's no secret that humans are having a huge impact on the life cycles of plants and animals. UC Santa Barbara researchers decided to test that theory by studying the world's far-flung islands. Their research sheds surprising light on the subject of extinction rates of species on islands.

In New Zealand, there were about 2,000 native species of plants, the researchers noted. Since colonization, about 2,000 new plant species have become naturalized. Over the same period, there have been few plant extinctions, so the net effect is that humans have transformed New Zealand's landscape by bringing in many new species.
Credit: iStockphoto/Richard Goerg

It's no secret that humans are having a huge impact on the life cycles of plants and animals. UC Santa Barbara's Steven D. Gaines and fellow researcher Dov Sax decided to test that theory by studying the world's far-flung islands.

Their research, published this month in the Proceedings of the National Academy of Sciences, sheds surprising light on the subject of extinction rates of species on islands. The paper, "Species Invasions and Extinction: The Future of Native Biodiversity on Islands," is one in a series of reports by this team studying how humans have altered the ecosystems of the planet.

Gaines and Sax started the project with a question: What effect are humans really having on biological diversity? "The presumption at the time was that we are driving biodiversity to lower levels," said Gaines, who directs UCSB's Marine Science Institute. "Certainly, if you think about it at the global level, this is true because humans have done a lot of things that have driven species extinct."

However, when studied on the smaller scale of islands, the findings showed something completely different. Diversity is on the rise – markedly so in some instances. Diversity has gone up so dramatically that it might cause some to wonder if the health of the ecosystems might not be better because the number of species is twice as high as it used to be. But it's not that simple, Gaines said.

"What Dov and I worked on a few years ago is the fact that the vast majority of introductions (of species) don't have large negative effects," Gaines said. "Indeed, most species that get introduced don't have much effect at all. It doesn't mean that they're not altering the ecosystem, but they're not driving things extinct like some of the big poster-child stories we've been hearing about."

Still, the study showed that human colonization has had a massive impact on ecosystems of islands, with the introduction of new, exotic plants and animals. In New Zealand, for example, there were about 2,000 native species of plants. Since colonization, about 2,000 new plant species have become naturalized. Over the same period, there have been few plant extinctions, so the net effect is that humans have transformed New Zealand's landscape by bringing in so many new species.

Sax, a former postdoctoral researcher at UCSB who is now assistant professor of ecology and evolutionary biology at Brown University, did much of the fact-finding for this report by painstakingly digging through data that had been collected over hundreds of years on islands around the world. "This is Dov's specialty," Gaines said. "Finding really old data sets that are very interesting."

"The dramatic increase in the number of species has changed how the system functions," Sax said. "Changing the abundance of natives versus exotics affects all of the other species that used to depend on the natives for food or shelter. So, it's not in any way to say that increasing biodiversity is a good thing."

With birds, it's a different story. The number of bird species on islands today is almost exactly the same as it was prior to human colonization, but the species of birds on the islands are very different. About 40 percent of the species of birds that you find on islands today are introduced species, Sax said, which means that a comparable number of birds has gone extinct. "In the case of birds," he said, "lots of extinctions, no change in total biodiversity."

All of this caused Gaines and Sax to ask new questions:

• Are the islands undersaturated? Can you still keep throwing species in there, with the result that nothing is going to happen?

• Are they now oversaturated? Are there limits in how many species an ecosystem can hold?

• Are we building an extinction debt? "Which means," Gaines said, "that by going in and mucking up the system, we may have already created the setting where too many species have been packed in, and we just haven't waited long enough to see these extinctions start to happen.

"The whole point of this study was to start looking down the path to see which of these wildly different scenarios might be right," Gaines added. "We haven't nailed the answer yet, but we've set the stage for answering whether islands are now saturated or not."

What made the research possible was that many of the explorers who colonized the islands included naturalists on their boats. From the time they landed on the islands, the naturalists were busy cataloging and documenting the plants and animals of each colony.

"It was very surprising to find such a strong correlation between the number of native and exotic plant species on islands around the world," Sax said. "In ecological research, a ‘strong' correlation often explains 50 percent of the variation. Here, the correlation between native and exotics explains almost 100 percent of the variation. In other words, if you know how many native plants are on an oceanic island then you can predict almost perfectly how many exotic plants are there."

The study, which took a year and a half, included islands such as Lord Howe Island east of Australia and Tristan da Cunha, a group of remote volcanic islands in the south Atlantic Ocean, among others.

"These were all oceanic islands," Gaines said, "which means islands that are far enough away from a continent that they're not getting regular exchanges with the mainland."


Story Source:

The above story is based on materials provided by University of California, Santa Barbara. Note: Materials may be edited for content and length.


Journal Reference:

  1. Dov F. Sax and Steven D. Gaines. Colloquium Paper: Species invasions and extinction: The future of native biodiversity on islands. Proceedings of the National Academy of Sciences, 2008; DOI: 10.1073/pnas.0802290105

Cite This Page:

University of California, Santa Barbara. "Is Extinction Or Diversity On The Rise? Study Of Islands Reveals Surprising Results." ScienceDaily. ScienceDaily, 27 August 2008. <www.sciencedaily.com/releases/2008/08/080826173227.htm>.
University of California, Santa Barbara. (2008, August 27). Is Extinction Or Diversity On The Rise? Study Of Islands Reveals Surprising Results. ScienceDaily. Retrieved August 21, 2014 from www.sciencedaily.com/releases/2008/08/080826173227.htm
University of California, Santa Barbara. "Is Extinction Or Diversity On The Rise? Study Of Islands Reveals Surprising Results." ScienceDaily. www.sciencedaily.com/releases/2008/08/080826173227.htm (accessed August 21, 2014).

Share This




More Plants & Animals News

Thursday, August 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Possible Ebola Patient in Isolation at California Hospital

Possible Ebola Patient in Isolation at California Hospital

Reuters - US Online Video (Aug. 20, 2014) — A patient who may have been exposed to the Ebola virus is in isolation at the Kaiser Permanente South Sacramento Medical Center. Linda So reports. Video provided by Reuters
Powered by NewsLook.com
Flower Power! Dandelions Make Car Tires?

Flower Power! Dandelions Make Car Tires?

Reuters - Business Video Online (Aug. 20, 2014) — Forget rolling on rubber, could car drivers soon be traveling on tires made from dandelions? Teams of scientists are racing to breed a type of the yellow flower whose taproot has a milky fluid with tire-grade rubber particles in it. As Joanna Partridge reports, global tire makers are investing millions in research into a new tire source. Video provided by Reuters
Powered by NewsLook.com
Unsustainable Elephant Poaching Killed 100K In 3 Years

Unsustainable Elephant Poaching Killed 100K In 3 Years

Newsy (Aug. 20, 2014) — Poachers have killed 100,000 elephants between 2010 and 2012, as the booming ivory trade takes its toll on the animals in Africa. Video provided by Newsy
Powered by NewsLook.com
Awesome New Camouflage Sheet Was Inspired By Octopus Skin

Awesome New Camouflage Sheet Was Inspired By Octopus Skin

Newsy (Aug. 19, 2014) — Scientists have developed a new device that mimics the way octopuses blend in with their surroundings to hide from dangerous predators. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins