As a result of human activity and climate change, ten of the world’s most protected forests have become net carbon emitters.
The startling revelation comes from a study of greenhouse gases emitted by and absorbed by forests in Unesco World Heritage sites. It was found that during the last 20 years, ten protected forests have emitted more carbon than they have stored. The woodlands of the world heritage site cover an area twice the size of Germany. According to the same study, the world’s 257 World Heritage forests collectively eliminated 190 million tonnes of carbon from the atmosphere per year.
The study by UNESCO, the World Resources Institute, and the International Union for Conservation of Nature (IUCN) revealed that land clearance and deforestation, as well as forest fires of increasing scale and severity, resulted in the trees releasing more carbon into the air than they stored.
Forests are important for reducing climate change because of their ability to act as carbon sinks. Trees and other plants remove greenhouse gases from the atmosphere by absorbing carbon dioxide and emitting oxygen. According to the study, which looked at a period from 2001 to 2020, all 257 forests together act as a net carbon sink.
Researchers calculated the carbon absorbed and emitted by World Heritage forests between 2001 and 2020 using satellite-derived data and site-level monitoring information. The investigation also revealed how much pressure some of these locations were under, in addition to estimating the billions of tonnes of carbon absorbed by all that “biomass” of trees and flora.
The places examined in this report have some of the most stringent levels of government protection. They are considered worldwide significant in terms of natural value and are rigorously and continually monitored.
“But they’re still under significant pressure,” Dr Carvalho Resende stated.
“The main pressures are agricultural encroachment, illegal logging – human-induced pressures.
“But we also found climate-related threats – most specifically wildfires.”
They discovered that World Heritage forests absorbed the equivalent of almost 190 million tonnes of carbon dioxide from the atmosphere each year, which is over half of the United Kingdom’s annual fossil-fuel emissions. However, they discovered that several locations, despite being net carbon sinks overall, had emissions spikes or evident increasing trajectories that jeopardised the future strength of the sink.
According to the report, forests not only absorb carbon dioxide from the atmosphere but also store significant amounts of carbon – around 13 billion tonnes, which is more than Kuwait’s proven oil reserves.
The researchers warned that prolonged human-caused landscape fragmentation and degradation would lead to more frequent and intense climate-related wildfires, and encouraged governments to strengthen protection and improve land management at World Heritage sites and their surrounding areas.
10 carbon-emitting World Heritage forests
- The Tropical Rainforest in Sumatra, Indonesia
- The Rio Platano Biosphere Reserve, Honduras
- Yosemite National Park, US
- Waterton Glacier International Peace Park, Canada and US
- The Barberton Makhonjwa Mountains, South Africa
- Kinabalu park, Malaysia
- The Uvs Nuur Basin, Russia and Mongolia
- Grand Canyon National Park, US
- The Greater Blue Mountains Area, Australia
- Morne Trois Pitons National Park, Dominica
How does carbon dioxide affect forests?
The carbon cycle in a specific forest (photosynthesis, plant respiration, and organic matter breakdown) is regulated by climatic conditions and CO2 concentrations in the atmosphere. It might be difficult to tell the difference between natural and human influences that influence plant growth. CO2 increases have a “fertilising effect” on photosynthesis and, as a result, plant growth. This explains current regional trends of increased forest development and results in an increase in plant carbon absorption. This also has an impact on the amount of the forest’s carbon pool.
How have humans artificially altered the carbon cycle?
The carbon cycle is greatly influenced by human activity. Carbon dioxide is released into the atmosphere via burning fossil fuels, changing land use, and using limestone to produce concrete. As a result, carbon dioxide levels in the atmosphere are fast increasing; they are already higher than they have been in the last 3.6 million years. Much of the carbon dioxide created by burning fossil fuels is absorbed by the ocean. Through a process known as ocean acidification, the excess carbon dioxide lowers the pH of the ocean. The ability of marine animals (such as corals, Dungeness crabs, and snails) to develop their shells and skeletons is harmed by ocean acidification.
How do forests affect the carbon cycle and climate?
Forests have a significant impact on climate change by influencing the amount of carbon dioxide in the atmosphere. Carbon is extracted from the atmosphere and absorbed in wood, leaves, and soil as forests expand. Forests (and oceans) are referred to as “carbon sinks” because they can absorb and store carbon for long periods of time. This carbon is kept in the forest environment, but when trees are burned, it can be released into the atmosphere. Understanding the global carbon cycle, and thus climate change requires quantifying the significant functions of forests in absorbing, storing, and releasing carbon.
How does the forest act as a carbon sink?
Forests act as CO2sinks, eliminating CO2 from the atmosphere, due to the process of photosynthesis2. CO2 from the atmosphere is fixed in the chlorophyll portions of the plant, and the carbon is subsequently integrated into complex organic compounds that are then utilised by the entire plant. When they increase biomass or expand their territory, they become CO2 sinks.
The biosphere of the planet acts as a carbon sink, absorbing about 2.3 GtC each year. This amounts to roughly 30% of total fossil fuel emissions (between 6.3 and 6.5 GtC/year) and is comparable to CO2 emissions caused by deforestation.
In 2017, Hurricane Maria destroyed an estimated 20% of the forest cover in Dominica’s Morne Trois Pitons National Park.
“There’s an alarming message from this study,” Dr Carvalho Resende remarked.
“Even the best and most protected forest areas in the world are threatened by the global climate crisis.
“So action [to cut global emissions] is really needed now to ensure that these forests – that all forests – can continue to act as carbon sinks and, of course, as important sites for biodiversity.”