MATSUYAMA--Global warming forced mikan farmer Junichiro Nishihara here into growing more heat-resistant avocados.

Nishihara, 62, started out producing mikan mandarin oranges and other crops, but he gradually began expanding his acreage of avocados after receiving seedlings of the fruit from the city government.

“I do have an emotional attachment as a citrus farmer, but I simply couldn’t make a living if I didn’t switch to crops that are adapted to the climate,” he said.

It had become more difficult for Nishihara to grow mikan, which, for example, have turned brown due to sunburn amid a succession of intensely hot summers over the past several years.

Nishihara also had difficulty growing avocados, which sometimes blossomed but didn’t bear fruit. But he now grows about 10 varieties of avocados on more than one-third of his farm that stretches 12,000 square meters.

Avocados are native to the subtropics and has earned the moniker of “forest butter” for their high nutritional value.

Nishihara sells some 1 ton of avocados online every year. He prices them at about 3,000 yen ($20) per kilogram (three to six pieces), about three times the price of mikan, but they are so sought-after that they sell out immediately, Nishihara said.

Avocados, by comparison, also require less effort for pest control and disease prevention and suffer less damage from heat, he explained.

Nishihara has been working, for several years now, on producing avocado seedlings himself and also growing bananas. He said he plans to stop growing mikan and switch to avocados and bananas in due course. 

SWITCH IN CROPS

Ehime Prefecture is renowned for being one of the leading mikan production centers in Japan.

However, amid global warming, major production areas for mikan in Japan will turn, by the end of this century, into areas suited to the cultivation of avocados, a subtropical fruit, according to a government-affiliated research institution.

Avocado culture has already started, under the support of local governments, in certain mikan-growing areas, foreshadowing the major impact of climate change on agriculture.

In Matsuyama, the capital of Ehime Prefecture, authorities began working, ahead of the rest of the nation, to establish an avocado production area in the city. 

They have been distributing avocado seedlings to farmers to encourage them to switch crops from mikan and other farm products.

The program, which was initially intended for effective use of idle farmland, is suddenly in the spotlight as the effects of global warming are starting to be felt.

SHIZUOKA’S AMBITION

In Shizuoka Prefecture, another major mikan-growing region, the governor is taking the initiative in seeking to turn his prefecture into Japan’s largest avocado production center in 10 years.

The prefectural government set aside a budget of 18 million yen for this fiscal year to work in earnest toward that goal.

Since Shizuoka Prefecture is located close to major consumption centers, avocados can be delivered to consumers in a fully ripened state if they are grown domestically.

Also, avocados can be grown outdoors, instead of being kept in a greenhouse, and they bear fruit only several years after seedlings are planted, which is less time than for mikan.

There is an urgent need, for the coming years, to seek avocado varieties that can survive Japan’s winter and to find out stable cultivation methods and quality control methods, officials said.

“We know so little about avocados, which are a subtropical farm product,” said Yuji Hirano, head of the Shizuoka prefectural government's Agricultural Strategy Division. “Somewhere between 10 and 20 farms are growing avocados in our prefecture. We will begin with working with prefectural research institutions to collect insights in three years.”

SUITABLE MIKAN GROWTH AREAS TO SHIFT NORTH

The National Agriculture and Food Research Organization (NARO) in March released forecast maps for areas suitable for growing mikan and avocados.

The forecasts showed that, in a worst-case scenario of global warming, what are currently major mandarin production centers will become unsuitable for growing mikan. However, areas suitable for cultivating avocados, the subtropical crop, are likely to expand dramatically.

Japan currently relies on imports for the most part of the avocados it consumes.

The NARO maps predicted suitable cultivation areas on a 1-kilometer-square grid.

NARO’s officials created models for evaluating the impact of temperatures on fruits and culture and conducted simulations for three of the five scenarios that were adopted in the Sixth Assessment Report of the Intergovernmental Panel on Climate Change.

The scenarios were delineated as having “very high,” “intermediate” and “low” greenhouse gas emissions.

Only areas with a narrow annual mean temperature range of 15 to 18 degrees are suitable for the growth of mikan. Excessively high temperatures result in sunburn and peel puffing.

Even a mere one-degree temperature rise can pose a risk, the officials said.

The simulations showed that, even in the “low” greenhouse gas emissions scenario, suitable mikan cultivation areas will gradually shift north.

By mid-century, the existing suitable areas along the Pacific coast of Kyushu and Honshu in and to the west of the Kanto region will expand further inland, whereas appropriate areas will also travel up the coastal areas on the Sea of Japan as far north as the Hokuriku region.

In the “intermediate” and “very high” greenhouse gas emissions scenarios, major production centers in Kagoshima, Ehime, Wakayama and Shizuoka prefectures will no longer be suitable for growing mikans toward the end of this century.

Kagoshima Prefecture is the purported home of the mikan. 

Now, Sado, Niigata Prefecture, and Himi, Toyama Prefecture, are among the locations that will emerge as newly suited to mikan culture.

BROAD AREAS SUITED TO AVOCADO GROWTH

Avocados, which are currently grown mostly only in limited areas of Japan, including the Nansei island chain in Kagoshima and Okinawa prefectures, are expected to replace mikan as a new crop suitable for cultivation.

The NARO officials predicted the areas suited to avocado culture will expand 2.5- to 3.7-fold from now by mid-century, and 2.4- to 7.7-fold from now by century-end, in the three scenarios considered.

They said that, in the “very high” greenhouse gas emissions scenario, some 95,000 square kilometers will fall in a temperature zone suited to avocado culture by the end of the century, and that includes larger parts of the Kanto plains and of Izu and Boso peninsulas.

“Even in a mikan production area that is no longer suitable for mikan culture, you can still continue growing the crop if you use shading, moisture control and other cultivation techniques and ingenuities, such as culling fruits in the upper and outer reaches of trees that are prone to high temperatures,” said Toshihiko Sugiura, a NARO agricultural meteorologist.

Sugiura, who works for NARO’s Institute of Fruit Tree and Tea Science, continued: “But doing so would be costly and take a lot of effort, and the mikan yield could drop. Switching to avocados is a viable option, even though that still comes with a number of challenges. It takes less labor to grow avocados, and there is high consumer demand for them.”

There are still other heat-resistant fruit species, but some of them, including the banana, are vulnerable to strong winds, such as typhoons.

Avocados have their drawbacks. For example, only a limited range of agrochemicals are authorized for use on the fruit, and it has yet to be established which avocado varieties are suited to Japan’s climate.

But avocados have the potential to be a farm product that could compete with foreign imports if it becomes possible to cultivate the crop at a stable quality, Sugiura said.

(This article was written by Nobufumi Yamada and Ryoko Takeishi.)