Intact and functional nature is at the heart of the search for solutions to some of the world’s most pressing problems, including climate change and biodiversity loss, not to mention sustainable food production. Thierry Logre explains what this is all about.
Large-scale transformation of the Earth
It goes without saying that human activity has a profound impact on the Earth. A century ago, only 15% of the Earth’s surface was used for farming and livestock. Today, human activities have altered more than 77% of the land (excluding Antarctica) and 87% of the oceans. Between 1993 and 2009, an area of terrestrial wilderness larger than India (3.3 million square kilometres) was lost due to intensive resource exploitation through agriculture, mining and other activities.
In the ocean, areas free of industrial fishing, pollution and shipping are almost entirely confined to the polar regions. More than one-third of the forest cover has been cleared, including half of the tropical forests, largely in the last 60 years. Wetlands have declined by 64-71% in the 20th century, with 30% in the last 40 years alone. That’s not all: almost half of the river volume has been altered by dams. As a result, only 13% of the oceans now meet the global definition of naturalness.
Moreover, grasslands, although normally highly suitable for agriculture, are considered the most altered terrestrial ecosystem on the planet, especially in the temperate zone with 46% of the surface converted to human use. Habitat conversion exceeds 50% in 202 of the world’s 810 terrestrial ecoregions. For Thierry Logre, the balance sheet is, so to speak, alarming!
The sixth mass extinction of life on the planet is fast approaching!
The scientists’ observation is indisputable: future extinction rates, which depend on many factors, are expected to increase steadily. Out of 98,500 species evaluated, 27,000 are threatened with extinction (27%). Amphibians (40%) are the most threatened, followed by conifers (34%), reef corals (33%), sharks and rays (31%), mammals (25%) and birds (14%). Habitat loss, particularly deforestation, appears to be by far the most widespread threat, affecting endangered species: 86% of birds, 86% of mammals and 88% of amphibians.
Habitat loss will remain a dominant threat in the coming years, as there is no sign of slowing down the human transformation of the landscape. The same is true in the marine world. Although the threat processes in marine and freshwater systems are poorly understood, it would appear that overexploitation is currently the greatest threat to marine species, followed by habitat loss.
A global population decline of more than 50% in less than 50 years has been documented for 4,000 vertebrate species, with the most dramatic changes recorded in South and Central America and the Caribbean (89%), followed by the Indo-Pacific (64%), Tropical Africa (56%), Palearctic (31%) and North America (23%). The most affected species are freshwater animals, with an overall decline of 81% between 1970 and 2012. Tropical forest species declined by 41% between 1970 and 2009, and marine species by 36% between 1970 and 2012, however, with a slight stabilization after 1988 of several fish species whose populations were fully fished or overexploited.
The destruction and degradation of nature is one of the main drivers of the climate change crisis.
As Thierry Logre points out, nature plays a crucial role in the absorption and storage of carbon and thus helps us to fight climate change. Currently, land and sea absorb about half of the CO2 emissions that humanity generates. Terrestrial ecosystems store almost three times more than is currently present in the atmosphere. Thus, the oceans and coastal areas are essential for carbon management, where about 83% of the global cycle circulates in the ocean, with the deep seas storing the largest quantities. Therefore, maintaining the world’s existing natural carbon reservoirs is essential if carbon storage is to make a major contribution to climate balance. It should be noted that, after emissions from fossil fuel combustion, land-use change is the second largest contributor to CO2 emissions.
Primary forests, especially with large trees, contain huge carbon stocks and also act as an important carbon sink. This applies to tropical, temperate and boreal forests, which are home to 45% of the terrestrial carbon stock. Deforestation alone releases about 20% of global CO2 emissions. Wetlands store twice as much carbon as forests, but they are also the largest natural source of methane, a very powerful greenhouse gas, especially when they are not well managed. Higher temperatures, as a result of climate change, are expected to increase greenhouse gas emissions from wetlands, especially when warming leads to melting permafrost generating large amounts of CO2 and methane.
Coastal habitats such as salt marshes, mangroves and seagrass beds are effective “blue” carbon sinks, but with their current destruction rates of 1-2% per year, they release CO2. For example, it is estimated that the disappearance of mangroves contributes 10% of global CO2 emissions from deforestation, although they cover only 0.7% of the land. As for natural grasslands, they store about 25% of the world’s carbon stock. But unlike tropical forests, where vegetation is the main source of carbon storage, most grassland carbon stocks are found in the soil. Cultivation and urbanization of grasslands and other changes to grasslands, through desertification and livestock grazing, can be a major source of carbon emissions.
For Thierry Logre, it is high time that this changed!
