Residents of Japan’s big cities, and of Tokyo in particular, are well aware of the heat-island effect — especially now with the onset of summer.
The effect occurs because concrete and asphalt retain radiant energy, making the whole city a vast absorber and then emitter of convected heat, which creates powerful thermals that trigger sudden “guerrilla storms” — and renders the nights barely more agreeable than the stifling, claggy days. And if you think summers have been getting worse — you’re right.
Figures from the Japan Meteorological Agency (JMA) show that annual average air temperatures nationwide rose by a rate equivalent to 1.15°C per century between 1898 and 2010. This is considerably higher than the global average temperature rise of 0.74°C over the last century (according to the Intergovernmental Panel on Climate Change’s “Climate Change 2007: Synthesis Report Summary for Policymakers”).
Not only have temperatures been rising in Japan, but they’ve been rising faster here than they have elsewhere — with some of that difference accounted for by the heat-island effect found in cities and dense urban areas.
I’ve just been looking at the first comprehensive report into the impacts of climate change in Japan. A few points jump out: Plants are flowering earlier each spring and, counterintuitively, insects are appearing later — perhaps because their pupal stages need a certain period of chilling in order to develop, so with winters getting warmer they take longer to develop. In addition, species’ ranges — the physical areas they inhabit — are expanding northward by between 18 km and 140 km per decade.
That report’s lead author is Yuko Ogawa-Onishi, who works at my old research base, the National Institute for Environmental Studies in Tsukuba, Ibaraki Prefecture, and at the University of Oxford. Ogawa-Onishi, with colleague Pam Berry at Oxford, reviewed as many publications as they could about observed and projected impacts of climate change in Japan, using both local and international publications.
By reviewing JMA weather-station data, the pair found evidence that the heat-island effect also occurs in relatively small cities. However, they point out that urban and industrial areas of Japan cover only 5 percent of the land area, while mountains, forests and agricultural regions account for more than 80 percent — so heating due to urbanization can only have a limited effect.
As for future conditions in Japan, they found some predictions suggest that, by 2100, temperatures are likely to increase by 2°C to 3°C (relative to a baseline average temperature between 1981 and 2000) — with summers getting wetter, and other seasons drier.
That’s bad, but a more pessimistic prediction — and by that I mean a mathematical model, not something someone has read in their tea leaves — has Japan’s mean temperature increasing by a whopping 4.8°C by 2100, with a 10 percent increase in rainfall.
Ogawa-Onishi and Berry’s report appears in the journal Biological Conservation (DOI: 10.1016/j.biocon.2012.06.024) — but what do its findings mean for iconic Japanese natural phenomena?
For cherry blossom, we’re looking at flowers coming 2.2 days earlier per decade. The first cicadas will sing 2.5 to 4.3 days later per decade. The Great Mormon swallowtail butterfly (Papilio memnon, okay so it’s not really iconic, but I like it) will move 130 km north per decade. Likewise, Sika deer (of Nara photo-op fame) will move northward.
“Plants and animals can adapt to climate change, but there is a limit,” says Ogawa-Onishi. “In southern Japan, we have already witnessed cherry trees not blooming after extremely warm winters, which indicates the limits to their adaptive capacity.”
Most people in Japan are very aware of the changes in natural events, in particular, the flowering of cherry trees.
Similarly, seasonal food is popular with most people in Japan, and they are aware that the availability of seasonal vegetables and certain fish at particular times of the year has changed. Some species can adapt, others can not adapt as well, says Ogawa-Onishi. Some things important to Japanese culture will certainly change.
But the changes that Ogawa-Onishi and Berry explore aren’t just important for pretty national emblems. Japan is a biological hotspot. With more than 90,000 species of fauna, flora and fungii in an area of 380,000 sq. km, it is a globally important biological region (which was one of the reasons I went to study insects in Japan — there are so many of them, and there are some very cool ones).
However, a major impact will be on the rice harvest, which will suffer a decrease of up to 40 percent in central and southern Japan. So rice imports will increase.
And, although if you travel around Japan you will find a profusion of paddy fields in rural areas, specialist foods everywhere you go, and every town seemingly famous for a certain fruit or fish — some 60 percent of the nation’s food is actually imported — and that proportion is set to rise.
For comparison, the United Kingdom imports about 25 percent of its food, and the United States exports more food than it imports.
In the face of this sort of ominous news, Oxford scientist Berry says there are easy ways to get involved and influence things for the better. She cites both the kind of steps that help reduce (mitigate) our impact, and ones that help adjust to the effect of climate change.
“There are simple mitigation actions that involve the use of less fuel, for example turning down the thermostat in winter or using less air conditioning in summer,” she says. Such advice may sound obvious, but a difference of 1°C can save about a ton of carbon emissions a year.
Meanwhile, switching off electronic devices rather then leaving them on standby can save 15 percent of a household’s energy bill. “Every little helps, and if enough people did these things there could be a real difference,” says Berry.
And there are ways to help species adapt to the effect of climate change. “People can help biodiversity by leaving some wild areas in their garden or planting wildflower mixes,” says Berry.
And she calls for us to make sure there are “permeable” areas in our towns and cities, and to plant trees and generally “greenify” our urban jungles.
Rowan Hooper (@rowhoop on Twitter) is the News Editor of New Scientist magazine. The second volume of Natural Selections columns translated into Japanese is published by Shinchosha at ¥1,500. The title is “Hito wa Ima mo Shinka Shiteru (The Evolving Human).”