The Yomiuri Shimbun Animals and plants subject to phenological observation — the tracking of seasonal natural phenomena — by the Japan Meteorological Agency are being spotted less often due to advancing urbanization. Barn swallows, for example, have gone unobserved the last two years in central Tokyo, and some animals have even been removed from the list of observed species due to a lack of sightings.
“These days, we have a hard time finding the animals we’ve been observing unless we look more carefully than before,” said an official at the Tokyo Regional Headquarters responsible for observations in central Tokyo.
The observations are carried out by 58 regional headquarters or weather stations across the nation. Officials search within a five-kilometer radius from their headquarters or stations and record the date they first observe a subject animal, hear a subject bird sing or observe a subject flower begin to bloom.
The meteorological agency has compiled data obtained throughout the nation since 1953, including on flowering cherry trees.
The Tokyo Regional Headquarters handles animal and plant observations in the Otemachi area and Kitanomaru Park near the Imperial Palace in central Tokyo.
Barn swallows, once observed around April each year, have not been spotted since 2015, while the Japanese bush warbler, dubbed “harutsugedori” or bird that heralds the coming of spring, was last confirmed by a headquarters official in 2000. The high-pitched buzzing of the evening cicada has not been heard since 2002.
While the meteorological agency lists 23 animals and plants as under phenological observation, some have been removed as targets in certain areas due to a rule that stipulates removing species that fail to meet such conditions as having been spotted “at least eight times in 30 years.”
In accordance with the rule, the Tokyo headquarters in 2011 removed six target species including the small white butterfly and skylark, leaving it to focus on five species: large brown cicada, Japanese bush warbler, common skimmer, barn swallow and evening cicada.
“Stain-resistant materials used for buildings and the lack of soil [in urban areas] seem to have created an environment unsuitable for living things to grow,” said the Tokyo headquarters official.
As a matter of fact, similar phenomena have occurred in provincial cities.
The Mito Meteorological Office in Mito has been unable to confirm the existence of black-spotted pond frogs since the last time they were seen in 2004. Until 2004, the meteorological office had confirmed the species appearing almost every year.
Similarly, the Choshi Local Meteorological Office in Choshi, Chiba Prefecture, has not recorded sightings of the frog species since 2011.
Before, the species had been confirmed in 45 prefectures, with these areas including Hokkaido but excluding Tokyo and Kanagawa Prefecture.
Last year, however, black-spotted pond frogs were only confirmed in Shiga and five other prefectures. From this year, the frog species will be removed from the list of observation targets in Kagawa Prefecture.
Fireflies have also disappeared in many places. Before, the insect species had been spotted in 44 prefectures, including Hokkaido. But now, fireflies are listed only in 33 prefectures as an observation target. Last year, the species could be confirmed only in 26 of these prefectures, including Kyoto and Fukuoka.
Regarding skylarks, their calls have not been heard for four years or longer in Ibaraki, Nagano and Hiroshima prefectures.
Osamu Mikami, an associate professor of Hokkaido University of Education who is an expert on biology, said the observation results “are important data to monitor global warming.”
Mikami added: “Rice paddies and farming fields preferred by many species have decreased even in provincial cities where meteorological offices are located, with habitat being rapidly lost. In this situation, it will be difficult for us to fully feel a sense of the seasons.”
Cherry blossom observations continue
In phenological observation, plants are one group of objects observed. The Japan Meteorological Agency also observes the flowering dates of cherry blossoms.
The date cherry blossoms bloom is defined as the first day when more than five or six flowers of sample trees have produced blossoms.
The sample tree in central Tokyo, used as the criterion to determine the blossom date, is located on the grounds of Yasukuni Shrine in Chiyoda Ward.
According to an announcement by the Japan Weather Association on Wednesday, cherry blossoms of the Someiyoshino variety in the Kanto region will likely bloom slightly earlier than usual this year.
The association predicted the bloom date would be March 23 in central Tokyo and Yokohama, three days earlier than normal.