Protecting and enhancing natural ecosystems can play a “small but significant” role in Canada reaching its carbon emissions targets, according to a new report released by the Council of Canadian Academies.
Canada is aiming to cut its greenhouse gas (GHG) emissions from 2005 levels by 40 to 45 per cent and become a country with net-zero emissions by 2050.
Environment and Climate Change Canada data released in 2020 showed Canada emitted 672 megatonnes of CO2, the largest component of GHG emissions, and to achieve its first target, Canada will need to reduce those levels to around 333.4 to 296.4 megatonnes.
The report from The Council of Canadian Academies (CCA) suggests that an estimated 6 per cent, or 40.3 megatonnes, of Canada’s current annual emissions, could be reduced by investing in natural landscapes and protecting ecosystems.
Nature-based climate solutions (NBCS) are ecosystems around Canada that naturally absorb and store carbon, like forests, wetlands and grasslands. They can absorb some of the human-caused emissions and are often referred to as "carbon sinks".
Depending on the type of ecosystem, the CCA estimates a range of its carbon-capturing power.
The CCA believes "full implementation" of protection and investment into NBCS can bring other benefits to Canadians on top of the carbon-capturing powers.
Some of the benefits include coastal flood control, improved air and water quality, reduced soil erosion, reduced heat-island effect, which is increased temperatures in urban areas due to less natural landscapes, and greater biodiversity.
"There's clear demonstration that these mitigation strategies, whether it's agriculture or forestry actually work," Susan Ziegler, professor of earth sciences at Memorial University of Newfoundland and CCA expert, told CTVNews.ca in a phone interview. "But that the co-benefits have the potential to be quite tremendous, with respect to protecting what we already have."
The report also notes that reducing climate emissions is the priority because if the environment continues to change, the disturbances to these ecosystems reduces the ability to absorb and store carbon.
The CCA broke down the Canadian landscape into categories and estimated the carbon mitigation power of each.
FORESTS
Canada's forests, stretching 347 million hectares, are under threat, according to the CCA, due to increased disturbances like forest fires, insects destroying trees and harvesting. These factors have contributed to Canada's forests absorbing less CO2.
Through photosynthesis, trees absorb carbon and transfer it below ground. Forests store carbon in three "pools"; belowground live biomass, standing and fallen dead wood and soil organic carbon.
"When all three pools are considered, Canada’s managed forests store approximately 208 tonnes of carbon per hectare," the report reads. "But the variability of carbon sequestration potential across Canada (e.g., by ecological zone, forest type, stand age, disturbance history) makes regional estimates more informative."
Managed forests, which are areas used for harvesting but undergo careful forest planning to ensure logging is done sustainably, make up 65 per cent of the total forests across the country. The CCA report notes that due to "large-scale" disturbances Canada's managed forests were estimated to be a net source of CO2.
"In recent years, factors such as wildfires, insect outbreaks, decreased rates of precipitation, and shifting annual harvest rates have contributed to Canada’s forests becoming carbon sources instead of sinks," the report reads.
Ziegler who studies Canada's boreal forests says this element of the report’s findings is "jarring."
"Canada has these globally significant, vast stores of carbon, but all these stores are linked to climate," she said. "They're linked to climate in ways that can enhance the uptake of that CO2 from the atmosphere or released more."
Some studies, like 'Large Soil Carbon Storage in Terrestrial Exosystems of Canada' published in Advancing Earth and Space Science, believe a "substantial" amount of carbon is buried deep beneath the surface. The report says there could be an estimated total carbon stock of 306 gigatonnes of carbon below Canada's forests.
Disturbances to the forests not only prevent trees from absorbing carbon properly, it also releases the CO2 stored by the ecosystem. Ziegler says the shift from a carbon sink to a source of carbon occurred in 2018 when 2,115 fires ravaged 1.35 million hectares of forests in B.C.
"The reason that we've gone from a sink for the boreal forests of Canada to a source is largely attributed to the tremendous amount of fires that we've had most recently," she said.
AGRICULTURE AND GRASSLANDS
Covering most of southern Alberta, Saskatchewan and the interior valleys of British Columbia, Canada's grasslands account for 6.2 million hectares of land.
The lands absorb and release carbon in response to certain factors, such as whether fertilizer is added. Because of this, the report says there are a range of opportunities to enhance carbon sequestration, which is when ecosystems absorb CO2 from the atmosphere and store it underground where it will be pressurized and become a liquid.
Similarly, agricultural areas, which cover 47 million hectares, also absorb and release carbon. Both ecosystems store CO2 in the soil below.
Because of the decomposition of plant matter in these areas, methane and carbon are both emitted in these ecosystems naturally. Agricultural lands in particular emit nitrous oxide (N2O), a by-product of nitrogen input into the soil via fertilizers. Nitrous oxide has 298 times the global warming potential of carbon dioxide, the report says.
"In 2020, agricultural soils in Canada were estimated to emit an average of 21 megatonnes of CO2 equivalent of nitrous oxide, compared to an estimated net cropland carbon sink of 9.6 megatonnes of CO2 equivalent," the report explains.
This means due to human disturbances and fertilizer, Canada's crops are emitting more GHG emissions than absorbing.
"One of the solutions…is paying attention to how natural ecosystems really work, and try to reduce those emissions from agricultural processes," Ziegler said. "(And to) take advantage of the natural soil environment to supply the nutrients that are required to get the crop."
Emissions from grasslands also happen but account for less than 0.05 megatonnes of CO2 equivalent in 2020, according to the report.
If protections are implemented, CCA's conservative estimate based on harvest timing and temperatures, Canada could see a sequestering rate of 0.025 to 0.64 tonnes of CO2 equivalent per hectare per year. If enhanced agricultural practices are not introduced, the ecosystems will continue to be carbon sources.
WETLANDS, LAKES, RIVERS
Canada contains about two-thirds of the total freshwater wetland area in North America, which is approximately 220 million hectares, the report says.
The soil found at the bottom of the wetland ecosystems is called peatlands, which is where carbon is stored. The edges of lakes and rivers also have peatlands, but it is not understood how much carbon can be stored within these ecosystems.
Both rivers and lakes emit CO2 and methane as they transport organic matter, such as leaves and wood, as it decomposes.
"There are large uncertainties surrounding estimates of carbon storage and rates of sequestration with respect to lakes and rivers," the report explains. "As such, the panel does not consider their restoration and conservation to be viable NBCSs due to these knowledge gaps."
However, the report notes that to understand carbon storage, conservation and protection of these often disturbed ecosystems should continue.
If further enhancement of the ecosystem occurs, the report's conservative estimate says Canada's lakes could store about 20 gigatonnes of carbon.
"The vulnerability of the carbon stocks and the role that natural climate solutions can play in promoting their protection is far beyond that 6 per cent (reduction in emissions)," Ziegler said.
Wetlands can absorb and store carbon over centuries, making them a critically important carbon sink in Canada. The report notes that many wetlands have been converted to other uses or damaged to the point of not being able to absorb as much CO2.
When peatlands are drained they become large emitters of the stored carbon, releasing about 16.3 tonnes of CO2 per hectare per year, which is equivalent to 3.8 homes' energy use for a year. Peatlands span 110 million hectares across Canada.
The exposed sediments continue to release CO2 into the atmosphere each year after the draining.
"In other words, every year post-drainage results in carbon losses that took (approximately) 70 years to accumulate," the report reads.
Because wetlands are extremely sensitive ecosystems, estimating how much carbon can be stored and absorbed by them is difficult. Researchers are only just starting to understand through on-the-ground experiments and testing how important these ecosystems are to Canada.
If Canada could avoid the further conversion of peatlands between 2020 and 2050, these systems could prevent the release of 199 megatonnes of CO2 equivalent per year, which is equivalent to 449 million of oil consumed.
MARINE COASTS
Canada's more than 240,000 kilometres of marine coastline offers a unique opportunity to store carbon, the experts reported.
These complex ecosystems can absorb and store carbon with some early research indicating salt marshes, seagrass meadows and mangroves can hold carbon for centuries.
Scientists and researchers have dubbed this "blue carbon."
Similarly to other carbon sinks, coastal ecosystems store carbon in peatlands, below-ground soil
"Peatlands (hold) thousands of years of tremendous amount of carbon," Ziegler said. "Some of our (Canada's) biggest stores are actually in the St. James Bay (Hudson's Bay) peatland complex."
What makes these ecosystems vital for Canada's emission targets is that if they are destroyed they can release the carbon stored into the atmosphere.
The Blue Carbon Initiative, an organization focused on saving coastal marine habitats, estimates when these ecosystems are degraded or destroyed as much as 1.02 billion tonnes of CO2 are released annually around the world, which is equivalent to more than 234 million homes' energy use for a year.
Research on blue carbon is slow to progress because of the hands-on research needed and testing in remote areas. Due to an early understanding of how carbon sinks are degraded by the changing climate, the report explains "there is a decreased carbon storage" when these ecosystems are under "stress."
The vast differences in annual temperature and environment on Canada’s coastlines, stretching from Newfoundland to Vancouver Island, and north to Hudson's Bay make estimates for the sequestration of carbon difficult.
Each ecosystem has delicate processes of how it captures and stores carbon indicating to experts that more research is needed to understand the power of these nature-based climate systems fully.
"Assessing the value of NBCSs will require regionally specific approaches for each of the Atlantic, Arctic, and Pacific coasts due to variations in vegetation, climate, and sea-level change," the report reads.
One estimate published in Science Advances in June 2021 called 'Natural climate solutions for Canada' explains blue carbon ecosystems can mitigate the release of 1.7 million tonnes of CO2 by the year 2030, which is the equivalent to 3.4 million barrels of oil.
"The natural ecosystems around U.S. and Canada are doing a lot of good already with respect for emissions, and we need to pay very close attention to that," Ziegler said. "I really hope that this (report) stimulates a lot of interest, and a lot of investment in further understanding these ecosystems."
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