For the study, scientists from Aarhus University, Iowa State University, the University of Maryland and Rice University used machine learning and data from thousands of field studies to map the contributions of seed-dispersing birds and mammals worldwide. To determine the severity of the declines, they compared recent maps of seed dispersal with maps showing what dispersal would look like without human-caused extinctions or species range restrictions.
Evan Fricke, the study's first author and an ecologist from Rice University, explained that while some plants live hundreds of years, their only chance to move is "during the short period when they're a seed moving across the landscape."
As human activity destroys the ecosystem, many plant species must relocate to a more suitable environment. However, plants that need seed dispersers may face extinction if there are too few animals to move their seeds far enough to keep up with changing conditions.
If no animals eat their fruits or carry away their nuts, animal-dispersed plants won't be able to travel far, explained Fricke.
Seed dispersion usually happens when animals eat fruits from plants or carry away their nuts, then excrete or drop the seeds elsewhere.
Other seeds have hooks or barbs that catch onto an animal's fur, feathers or skin. In tropical rainforests, animals disperse the seeds of at least 90 percent of tree species.
Fricke explained that many plants people rely on economically and ecologically need help from various seed-dispersing birds and mammals.
Identifying the scale of the seed-dispersal problem globally
This study is the first of its kind to "quantify the scale of the seed-dispersal problem globally and to identify the regions most affected," said Fricke.
The researchers used data from thousands of studies that focused on how many seeds specific species of birds and mammals disperse, how far they disperse them and how well those seeds germinate. (Related: Conservationists study rare species to understand how biodiversity protects ecosystems – and humans.)
Doug Levey, program director of the National Science Foundation's (NSF) Directorate for Biological Sciences, which partially funded the work, explained that the study is a necessary wake-up call about how declines in animal species have significantly limited the ability of plants to adapt to changing ecological conditions. The study also helped show how effective complex analyses are when applied to "huge, publicly available data."
Findings revealed that there were significant seed-dispersal losses in temperate regions across North America, Europe, South America and Australia. If endangered species go extinct, the tropical regions in South America, Africa and Southeast Asia would be most affected.
According to Fricke, there were regions where climate-tracking seed dispersal declined by a staggering 95 percent, even though they only lost a few percent of their mammal and bird species.
Additionally, seed-dispersal declines emphasize a crucial ramification of the human-caused destruction of animal biodiversity via habitat destruction and global pollution.
The biodiversity of seed-dispersing animals has a large role in the climate resilience of plants, which includes their ability to continue storing carbon and feeding people. Fricke believes ecosystem restoration can help improve the connectivity of natural habitats to rectify some declines in seed dispersal.
Jens-Christian Svenning, the study's senior author and a professor and director at Aarhus University's Center for Biodiversity Dynamics in a Changing World, added that large mammals and birds are also very important as long-distance seed dispersers. Unfortunately, many "have been widely lost from natural ecosystems."
Much of this research is being described in the false context of "climate change" when it is really about the mass die-off of animals and pollinators due to pesticides, pollution and habitat destruction.
Watch the video below to know more about the impact of climate change on biodiversity.
This video is from the Finding Genius Podcast channel on Brighteon.com.
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