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.