UK flowers have bloomed earlier over the past 25 years than any other period since 1760, threatening pollinating insects and other creatures depending on them for food. An international team including researchers from Cambridge University and the UK’s Woodland Trust found that overall they flowered 2.2 days earlier than in 1910-1934, the previous earliest-blooming 25-year period. The team, led by Tatsuya Amano of Cambridge and Japan’s National Institute for Agro-Environmental Sciences, also found that the current period’s flowering is 12.7 days earlier than the latest-blooming period, 1835–1859.
“There is a clear advance in the time of first flowering in recent decades,” Amano and colleagues write in a paper published online in the journal Royal Society Proceedings B on Wednesday. The timing changes could cause insects to miss out on their usual pollen supplies, in turn affecting birds for which insects and flowers are food sources. “This situation is critical,” Amano and colleagues write, “possibly leading to an increase in extinction risks.”
Their results show that flowering advances 5 days per 1ºC rise in temperature, matching results published elsewhere. They note that this kind of long-term perspective on the effects of global warming is unusual, which can be a problem. “Conclusions about the impact of climate change based on short-term observations can be misleading,” they write. “The 250-year index developed in this study should provide an important context for investigating ongoing responses to climate change.”
The researchers gathered 395,466 observation records of annual first flowering dates for 405 types of flower from 1753 to date at sites throughout the UK. The information was provided by the UK Phenology Network, which sprung from the work of individual observers to become a national network from 1875 to 1947. It was re-established in 1998, with the Woodland Trust bringing the project to the internet, co-ordinating approximately 40,000 recorders in the UK today.
The team highlight the advantages of their approach over the only official UK government index on phenology – the study of recurring natural events – that covers just four plant and animal species. This may be too small to accurately reflect broader scale events, the scientists say, and means that missing any data would make it impossible to create an index for that year. “Given the presence of numerous phenological observation networks all over the world, future efforts should be directed towards creating indices across regions.” they suggest.
Meanwhile, two papers published this week look at emissions of the less well-known greenhouse gas nitrous oxide – also known as laughing gas – from natural sources. On Sunday, Danish and Norwegian researchers wrote in Nature Geoscience about nitrous oxide release from the thawing of permanently frozen earth known as permafrost. The scientists, led by Bo Elberling of the University of Copenhagen, point out that all over the planet biological processes produce nitrous oxide from soil.
Previously, it had been thought that thawing permafrost had little effect on nitrous oxide emissions. However their studies, performed at Zackenberg in north-eastern Greenland, show that the thawing actually produces it in large amounts. “Microorganisms capable of producing laughing gas are apparently already present in the permafrost,” Elberling explained. These are able to break down surprisingly high levels of nitrogen chemicals the team found dissolved in the permafrost’s ice into nitrous oxide and release it into the atmosphere when it melts. “We conclude that future climate change in Zackenberg is likely to increase permafrost thawing and increase nitrous oxide production and release to the atmosphere,” the team writes.
In the second nitrous oxide paper, published on Wednesday, a team of researchers from Germany, China and the UK have studied the effect grazing animals have on nitrous oxide production. “Atmospheric concentrations of nitrous oxide have increased significantly since pre-industrial times, with animal production being one of the main contributors,” write the team in Nature this week.
Klaus Butterbach-Bahl of the Karlsruhe Institute of Technology and his colleagues took a year’s measurements of nitrous oxide emissions in the steppe grassland of Inner Mongolia. They found that most of the annual nitrous oxide emitted is released during the spring thaw, but that the amount released declines the more animals there are grazing on the land. Any increase in nitrous oxide levels directly caused by livestock seems to be offset by the overall reduction in nitrogen cycling caused by grazing over the year. “By neglecting these freeze–thaw interactions, existing approaches may have systematically overestimated nitrous oxide emissions over the last century for semi-arid, cool temperate grasslands by up to 72 per cent,” Butterbach-Bahl and his colleagues write.