Interactive effects of changes in UV radiation and climate on terrestrial ecosystems, biogeochemical cycles, and feedbacks to the climate system

Abstract

Terrestrial organisms and ecosystems are being exposed to new and rapidly changing combinations of solar UV radiation and other environmental factors because of ongoing changes in stratospheric ozone and climate. In this Quadrennial Assessment, we examine the interactive effects of changes in stratospheric ozone, UV radiation and climate on terrestrial ecosystems and biogeochemical cycles in the context of the Montreal Protocol. We specifically assess effects on terrestrial organisms, agriculture and food supply, biodiversity, ecosystem services and feedbacks to the climate system. Emphasis is placed on the role of extreme climate events in altering the exposure to UV radiation of organisms and ecosystems and the potential effects on biodiversity. We also address the responses of plants to increased temporal variability in solar UV radiation, the interactive effects of UV radiation and other climate change factors (e.g. drought, temperature) on crops, and the role of UV radiation in driving the breakdown of organic matter from dead plant material (i.e. litter) and biocides (pesticides and herbicides). Our assessment indicates that UV radiation and climate interact in various ways to affect the structure and function of terrestrial ecosystems, and that by protecting the ozone layer, the Montreal Protocol continues to play a vital role in maintaining healthy, diverse ecosystems on land that sustain life on Earth. Furthermore, the Montreal Protocol and its Kigali Amendment are mitigating some of the negative environmental consequences of climate change by limiting the emissions of greenhouse gases and protecting the carbon sequestration potential of vegetation and the terrestrial carbon pool. Graphical abstract

Stratospheric ozone, UV radiation, and climate interactions

“…Furthermore, experiments (summarized by Ballaré et al [ 91 ]) have not yet established whether the assumed sensitivity of plants to increases in UV-B radiation (i.e., a 3% reduction in biomass for every 10% increase in UV-B radiation for the “reference” scenario considered by Young et al [ 90 ]) can be extrapolated to the very large increases in UV-B radiation simulated in this study. For example, Young et al [ 90 ] did not consider that plants have protective mechanisms against damaging amounts of UV radiation, e.g., by synthesizing UV-absorbing compounds [e.g., 3 , 92 – 95 ]. Such adaptation would mitigate the net CO 2 flux into the atmosphere.…”

“…Conversely, enhanced photodegradation of organic matter under elevated UV radiation would release additional CO 2 into the atmosphere [ 96 ]. For more details, see Box 1 of Barnes et al [ 3 ].…”

“…Measurements at Palmer Station were highly variable, as is typical for this site, but new records were also set at this site in the second half of November 2020 when the center of the ozone hole was above the station. High UV radiation at this time, which coincides with the start of the growing season for plants and the peak breeding season for most animals, is a concern [ 3 ].…”

“…It focuses on the effects of changes in the ozone layer on climate and ultraviolet (UV) radiation at the Earth’s surface, the interactions between UV radiation and climate, and on the influence of other geophysical parameters affecting UV radiation. This assessment sets the stage for subsequent assessments in this series that address the consequences of the interconnected effects of stratospheric ozone depletion, UV radiation, and climate change on human health [ 1 ] (including the COVID-19 pandemic [ 2 ]), terrestrial [ 3 ] and aquatic [ 4 ] ecosystems, the carbon cycle [ 3 , 4 ], air quality [ 5 ], natural and synthetic materials [ 6 ], and the fate of environmental plastic debris [ 7 ]. These assessments focus on new scientific knowledge that has accumulated since our last comprehensive assessment ( Photochem.…”

Linkages between COVID-19, solar UV radiation, and the Montreal Protocol

“…6). On the other hand, the far-reaching, positive outcomes of the successful implementation of the Montreal Protocol for life on Earth [25,93,[110][111][112][113][114] outweigh any potential advantage for disinfection by higher amounts of solar UV radiation.…”