Biodiversity collapse in the tropics
July 25, 2018
A current study suggests that the damage to biodiversity in the tropics could even be worse than expected if we don't get a grip on the environmental problems there.
An international team of researchers from around the world put a figure on biodiversity in tropical regions, looking at forests, savannahs, freshwater regions and coastlines.
Their results: Even though the tropics cover only about 40 percent of the Earth's surface, they harbor a whopping 78 percent of all plant and animal species, including amphibians, terrestrial mammals, fish, ants and flowering plants.
And these tropical regions are even more important for birds: 91 percent of all terrestrial birds live in those warm and humid zones. Many more living elsewhere cross or visit the tropics on their annual migrations.
The tropics are also home of almost all shallow-water corals known so far.
Most of these tropical species are found nowhere else, and researchers estimate that at least 150,000 species are as yet unknown to science.
Read more: Scientists race to name unknown species before biodiversity disappears
"At the current rate of species description — about 20,000 new species per year — it can be estimated that at least 300 years will be necessary to catalogue biodiversity," Benoit Guénard, assistant professor of the University of Hong Kong, says in a press release accompanying the study.
"We have far less knowledge on the species that live in the tropics compared to those in temperate areas," Yves Basset, researcher with Smithsonian Tropical Research Institute, who was not involved in the study, tells DW.
"But we know that the majority of species live in the tropics," he says adding that this is also true for insects — the animals that he focuses on in his research.
There are many hypothesis on why so many more species have evolved in the tropics.
But those "hyperdiverse tropical ecosystems" — as the researchers call them — are disappearing.
Tropics in trouble
Deforestation, pollution, overfishing, overhunting, invasive species and ultimately global warming are all taking their toll on tropical ecosystems.
Read more: Five of the world's biggest environmental problems
"They are undergoing drastic transition, changing from what they were before, to something completely different," lead author Jos Barlow from Lancaster University tells DW.
Coral reefs, for example, get overgrown and finally replaced by fields of algae and sponges.
Wildfires in humid tropical forests, which used to be fire-free in the past, can result in grassy vegetation taking over.
In many savannas such as the Brazilian Cerrado, in turn, trees planted for harvest are taking over the ecosystem.
"These events are happening now, and they are happening with greater frequencies and with larger extents over time," Barlow says.
This loss of ecosystem can have dramatic negative effects for humans as well, the researchers add.
Coral reefs, for example, provide fish resources for the 275 million people that live within 30 kilometers (19 miles) of them while forests provide timber and other products. And the evaporation in Amazonia is estimated to provide 70 percent of the rainfall in the 3.2-million square kilometer area next to it.
Tropical ecosystems are already contending with many local threats, such as pollution and logging. Climate change might be the last straw.
"While most of us are familiar with the impact of climate change on the polar regions, it is also having devastating consequences across the tropics — and without urgent action, could undermine local conservation," Barlow says.
Read more: Climate change threatens half of wildlife in biodiversity hotspots, study says
Multiple stressors, such as pollution and global warming "can interact in myriad ways," the researchers write.
In such cases, a collapse becomes imminent.
Asked what he most urgently wished for to preserve the tropics, Jos Barlow answers: "to control climate change."
Current environmental action not enough
Establishing protected areas is one approach to conserving biodiversity.
The world has seen an "enormous increase" in coverage of protected areas, both terrestrial and marine, Barlow points out. "These are extremely important, and have huge potential to preserve and conserve biodiversity." he says.
But nature reserves alone are not the solution.
The study finds that the current network of proected areas remains poorly designed and covers too little tropical freshwaters and grasslands.
Moreover, protecting only what's inside the boundaries of a nature reserve, doesn't prevent biodiversity loss outside.
This strategy "fails to engage with the distal drivers of bioversity loss," they write in Nature.
Those drivers include population growth, deeply rooted inequalities between developed and developing countries, and the increasing value of natural resources coming from the tropics, such as timber, soy beans, palm oil or even the scales of a pangolin.
Christina Hicks from Lancaster University said in the press release that industrialized countries play a huge role in causing environmental problems in the tropics. Environmental aid has been "static" in recent years, "and remains a drop in the ocean compared to the income generated by resource extraction."
Multinational efforts required
The researchers call for a joint approach to managing resources and ecosystems.
"We need multinational efforts that span borders, because many of these issues aren't constrained within a particular country," Barlow says.
Understanding and controlling supply chains might be a key measure, making sure that the products we buy in European or US stores don't harm the environment in the tropics.
"Consumer information is really important, but also legal requirements preventing the import of products that show unsustainable supply chains."
The researchers praise France's radical new law loi de vigilance. It imposes due diligence on multinational corporations to prevent serious human rights abuses and environmental risks in their supply chains that extend beyond French borders.
Read more: The difficult task of tracking deadly wood
Barlow says there is still hope to preserve the tropics as the biodiversity treasure trove that it is now.
"If you go to the tropics now, you can still see this wonderful biodiversity. However, we really need to act soon and change the way we are approaching its conservation."