Reducing Methane Emissions is One of the Most Powerful Tools in the Global Fight Against Ecosystem Degradation

With around one million animal and plant species threatened with extinction, many within decades, it is fitting that the theme of this year’s World Environment Day is ‘ecosystem restoration,’ with the aim of supporting the reversal of ecosystem damage around the globe. 

Ecosystem services are the myriad benefits that humans enjoy from the natural environment, including things like clean air, climate regulation, food, and clean water. Human activity is threatening these ecosystem services, including through the emissions of short-lived climate pollutants like methane, a central ingredient in ground-level ozone, both of which are powerful climate forcers. Ozone is additionally a harmful air pollutant with a significant impact on ecosystems worldwide.

“Methane is increasing dramatically— at the fastest rate since records started being kept in the 1980s. This is having knock-on effects for ozone, which is seeing substantial increases in those parts of the world where emissions of other ozone precursors are also high. One of the most important things we can do to protect the planet’s vital ecosystems over the coming decades is dramatically reduce methane emissions,” said Drew Shindell, the current Chair of the Climate and Clean Air Coalition (CCAC) Scientific Advisory Panel. “These short-lived climate pollutants hit ecosystems hard in the short-term through the negative effects of air pollution and also in the longer term by contributing to global warming.”

Today also marks the beginning of the UN Decade on Ecosystem Restoration 2021 – 2030, a worldwide push to live more harmoniously with nature. Ecosystem restoration can take a variety of different forms— from planting native tree species to combat the 4.7 million hectares of tropical forest lost every year, to using tillage and crop rotation to help restore the farmlands that now cover a third of the land’s surface, to better waste management to keep pollutants and plastics out of oceans, to reducing vehicle emissions in cities.

The CCAC’s efforts are playing an important role in ecosystem regeneration, with contributions from a diverse array of measures. These range from the work to eliminate black carbon and fine particulate matter from heavy-duty vehicles by 2030, to promoting efficient rice production, to a broad suite of policies reducing methane emissions, to programmes to help cities divert organic waste and prevent open burning.

Countries around the world are joining in on the efforts. Pakistan, for example, is the host of this year’s World Environment Day and is setting out to restore its forests with the 10 Billion Tree Tsunami, which seeks to restore mangroves and forests while also planting trees in public urban areas. Pakistan, a CCAC member since 2017, has been working with the Coalition to elevate industry awareness of the cost effective technologies to produce bricks without spewing high levels of black carbon and other pollutants into the atmosphere.

If global human-driven methane emissions were reduced by 45 percent by 2030, it could prevent 26 million tonnes of staple crop losses every year. The benefits of these reductions are multiple, with the potential to also prevent 255,000 deaths from respiratory and cardiovascular diseases and 775,000 asthma-related hospital visits (due to reduced ozone). An estimated 73 billion lost work hours due to heat exposure would also be prevented.

We know all this because this month, the Climate and Clean Air Coalition released the Global Methane Assessment, which for the first time integrates the climate and air pollution costs and benefits of methane mitigation.

Estimates of the loss on staple crops such as rice, wheat, and soy as a result of ozone ranges from 3-16 percent, or $14 to $26 billion lost. But this is far from the pollutants' only effect on ecosystems.

“Methane is a primary determinant of ground-level ozone concentrations and those ozone concentrations will have impacts on a variety of ecosystem services,” said Professor Lisa Emberson of the Department of Environment & Geography at the University of York in the United Kingdom. “In quantifying the benefits of methane reductions and hence ozone reductions we have a tendency so far to focus on crop yields but there are a whole load of other ecosystem services that would also benefit: crop nutritional quality, fertilizer use efficiency, forage quality for livestock, terrestrial carbon sequestration, and catchment hydrology.”

The damage that ground-level ozone causes to plants and ecosystems ranges from physically injuring leaves, to reduced chlorophyll content, reduced biomass, reduced yield quantity, and even reduced nutritional content. Wheat yield losses due to current day versus pre-industrial ozone concentrations are estimated at 8.4 percent and ozone could be reducing soybean seed protein by 200 kilograms of protein per hectare. Livestock are impacted because the pastures they graze on are affected by ozone, which reduces the ratio of nutritionally rich clover to grass. In the United Kingdom, for example, one study found that ozone reduced lamb production by 4 percent between 2007 and 2020.

Forests have also been substantially affected by ozone concentrations. Increased ground-level ozone since preindustrial times is estimated to have reduced woody biomass by 7 percent globally. Ozone can affect tree growth and productivity, and may contribute to increased mortality. It can also alter species dominance which can influence drought and fire suppression and can heighten the overall forests’ vulnerability to drought and pest attacks. Particularly concerning for potential climate change impacts is that ozone also appears to reduce carbon sequestration.

While there is still limited research on this topic, ozone also threatens biodiversity, with 40 percent of global terrestrial ecoregions, or areas with very high species richness, exposed to high ozone concentrations.

“It shows some of the knowledge gaps that we have: less than about 1 percent of the species in those highly diverse ecosystems have had some sort of assessment of their ozone sensitivity, so we really don't know how big of a problem this potentially is,” said Emberson. “But the chance that there’s a fairly substantial threat to biodiversity means that taking action on a pollutant that we know how to deal with, and would have multiple benefits for human health and climate change in the very near term would seem a very good thing to do.”

Like many researchers, Emberson worries how climate change will exacerbate some of these effects.

“Ozone pollution is at high concentration when you have hot, dry, sunny conditions, which are likely to occur more frequently in the future with climate change,” said Emberson. “You have a situation where air pollution is likely to occur at the same time as other extreme weather events which will create combined stress on ecosystems, crops, and pastures.”

A new report from the WWF finds that if global warming reaches more than 1.5 degrees Celsius above pre-industrial levels it will cause dangerous habitat loss and food insecurity for many species around the world, including sea turtles, hippos, monkeys, frogs, and puffins. Commercial crops will be affected too: The land in South America where coffee can grow could drop by 88 percent. 

Reducing short-lived climate pollutants is key to keep warming below 1.5 degrees. Methane reduction is particularly critical here too, given that it is responsible for about 30 percent of direct warming since pre-industrial times. As is always the case with short-lived climate pollutants, the losses are dramatic, but so are the potential gains: a 45 percent reduction in methane emissions could result in about 26 million additional tons of grain production annually. Methane doesn’t last very long in the atmosphere which means that the effects of reductions can be rapid.

The Global Methane Assessment is an important tool here too because it identifies measures to reduce methane emissions rapidly and effectively through the three major emitting sectors: fossil fuels, waste, and agriculture. These reductions can be achieved through technology already at our disposal, such as preventing leaks and capturing methane in the oil and gas industry, and could reduce methane emissions by 45 percent by 2030. Moreover, about 60 percent of these measures are low cost and 50 percent of those have negative costs.

“These measures are readily available to us and would deliver benefits quickly. That speed is crucial because we need to make major changes this decade to avoid the kind of catastrophic warming that could lead to extinctions of many species and further degradation of our vital ecosystems that help us have clean air to breathe, diverse and nutritional food to eat, and a stable climate that supports all species,” said Shindell.