Earth's sixth mass extinction will be happening sometime in the not too distant future and scientists warn that the loss and decline of numerous animal species can be blamed on two contributing factors: habitat loss and climate change. A July 24 Science Daily report indicates that it appears that we are in the early days of the planet's sixth mass biological extinction event. Since 1500, over 320 terrestrial vertebrates have become extinct and the populations of the other species show an average decrease of 25 percent in abundance, the report explained.
The study, published in the journal Science and led by the U.K.'s University College London and Stanford University, focused on the disappearance of invertebrates, particularly because vertebrates have been studied extensively. Although researchers found similar widespread changes in both, the steady decline in invertebrate species surprised scientists because, previously, they had been seen as survivors of nature.
In the UK alone, scientists observed that in areas inhabited by common insects such as beetles, butterflies, bees and wasps, there has been a decline of between 30 and 60 percent in the past 40 years. The drastic reduction of these species largely endangers nature's capability to provide humans of things they need.
"We were shocked to find similar losses in invertebrates as with larger animals, as we previously thought invertebrates to be more resilient." said Ben Collen of the U.K.'s University College London, one of the study authors.
In economic terms, these animals provide important services to humans. For example, insect pollination is required in 75 percent of all food crops in the world and is estimated to be worth about 10 percent of the economic value of the entire world's food supply. Globally, pollinators seem to be declining sharply in abundance and diversity.
In the United States alone, the value of pest control by native predators is estimated at $4.5 billion annually, a cost that could increase with the decrease in the number of predators. In addition, insects and vertebrates (such as birds) are important for nutrient cycling over long distances. The decline of this key role in nature greatly compromises the integrity of other ecosystem functions such as productivity of plants.
Meanwhile, the decline of the amphibian population has led to increased algae biomass and wastewater, which in turn reduces the absorption of nitrogen.
"We tend to think about extinction as loss of a species from the face of Earth, and that's very important, but there's a loss of critical ecosystem functioning in which animals play a central role that we need to pay attention to as well," said lead author Rodolfo Dirzo of Stanford University.
Scientists believe there is a growing understanding of how ecosystems are changing. But to deal with these problems, better predictions of the impact of changes are needed together with effective policies to reverse the currently observed losses.
Dirzo also said that what's new about this extinction is "that the underlying driving force for this is not a meteorite or a mega-volcanic eruption; it is one species - homo sapiens."