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Kunihisa Morinaga
Research manager,
National Agricultural Research Organization (NARO),
Tsukuba, Ibaraki 305-8605, Japan

ABSTRACT

Intergovernmental Panel on Climate Change (IPCC) reported that the global mean temperature had risen for the 20th century at the rate of 0.74ºC per 100 years due to increasing green house gas. Climate change such as temperature, precipitation and tropical cyclone activity has been strongly related to agricultural production, water resource, and species diversity. Recent climate change has already affected all agricultural crops and animal production in Japan. Horticultural crops, vegetables and fruits, having high priority of quality, had serious effects in Japan, due mainly to high temperature. We have been researching the impact of climate change on horticultural crops and developing several technological countermeasures and new varieties and cultivars which have tolerance against high temperature.

Key words: Climate change, global warming, horticulture, countermeasures

INTRODUCTION

Global warming is becoming a worldwide concern, particularly, after the (IPCC) 4th Assessment Report in 2007. The rise of temperature has been felt much more clearly after 1990. Effects of global warming on fruit trees and vegetable production in Japan have recently appeared. This report, therefore, covers assessments of global warming impacts on horticultural crops in the past and future, and Japan's countermeasures.

Global warming has already negatively effected agriculture throughout Japan. In rice production, stable crops, abnormal grains called chalky and cracked grains are induced by high temperature during summer which is the crops' ripening stages. Tropical and sub-tropical diseases that had been rarely seen are now common in the southern part of Japan.

Perennial crops such as fruit trees have faced very serious damage due to global warming, throughout a year even in winter season. Qualities of fruits have clearly changed. For example, peel coloring disorder, too much enlarging, and reduction of acid, softening and spoiling rapidly of fruits have been observed more frequently. On the contrary, freezing injury and late frost damage have increased in north Japan which is a colder area. It is predicted that the favorable regions to cultivate apples and Satsuma mandarins will gradually move northward.

In vegetable production, disorder of eggplants such as bad bearing and growth, are also caused by high temperature. In addition, decrease of yield in fruits and low fruit quality, and malformed fruits are serious problems in Japan.

Therefore, some adaptation techniques to mitigate the effects of global warming have been developed. Problems and practical approaches against negative impacts of global warming on horticultural crops in Japan are reviewed.

CLIMATE CHANGE IN THE WORLD AND JAPAN

IPCC estimated that global mean surface temperature have risen by 0.74 ºC±0.18 ºC when estimated by a linear trend over the last 100 years and the warming rate during last 50 years is almost double that of the last 100 years (Fig. 1 and Fig. 2).

According to the regional climate report of IPCC (2007), the entire Asian region is very likely to warm during the last 100 years. The temperature is likely to be above the mean in East and South Asia, and similar to the mean temperature in Southeast Asia.

In addition, extreme precipitation and winds are increasing in East, Southeast and South Asia.

Japan Meteorological Agency reported that the mean temperature in Japan had risen at the rate of 1.07ºC per 100 years for the 20th century (Fig. 1). The average summer temperature in Korea showed that it was 23.5ºC in 1970s and 24.0ºC in 2000s indicating that there was increase in summer temperature (2009).

IPCC (2007) also reported that global average surface air temperature will rise for the 21st century at 1.8-4.0ºC by the increasing concentration of greenhouse gases in the atmosphere. Agricultural production is at risk of experiencing the various negative effects of global warming.

RECENT EFFECTS OF GLOBAL WARMING ON AGRICULTURE AND HORTICULTURAL CROPS IN JAPAN

To collect information about phenological changes in horticultural crops such as fruit trees, vegetables and flower production, and problems caused by the recent warming in Japan, Sugiura et al. (2006) sent a questionnaire to prefectural institutes for fruit tree research. All 47 prefectures in Japan replied that the recent warming had affected at least one tree species. This result shows that global warming have already effected the agriculture industry in Japan (Fig. 3). The impacts had particularly extended to horticultural crops such as fruit trees, vegetables and flowers.

Tree species are classified into two types by responses of fruit development to climate changes. One group is the earlier development type and the other is the prolonged development type. The former are tree species in which both flowering and harvesting periods have accelerated. These include Japanese pears, peaches and Japanese apricots. The latter are tree species in which the flowering periods have accelerated, while harvestingperiods have not accelerated. This type includes apples, Japanese persimmons, grapes and Satsuma mandarins. Fruit qualities of the prolonged development type have clearly changed, for example coloring disorder, enlargement, and reduction of acid which soften and spoil the fruits rapidly (Fig. 4). Freezing injury and late frost damage have increased in north Japan which is the colder area. It is predicted that the favorable regions to cultivate apples and Satsuma mandarins will gradually move northward. Therefore, some adaptation techniques to global warming have been developing continuously.

Delay of endodormancy breaking and disorder of budding did not occur in open field but occured only in the laboratory. Budding period and flowering period have accelerated in almost all tree species (Table 1. and Fig.5).

Changes of fruit quality such as enlargement of fruit size, reduction of acid and persimmon astringency, softening of flesh, rapid spoiling and increasing of sunscald were observed on a number of tree species. Fruit skin coloring have been delayed and disordered in apples, grapes, Japanese persimmons and Satsuma mandarins (Table 2).

Since citrus greening disease (Huanglongbing, HLB) was first detected in Iriomote Island 1988 in Japan, the disease spread throughout the southern islands of Japan, where Diaphorina citri (citrus psylla) had been distributed. In 2002, a D. citri population was found in Yakushima on hedge plants of Murraya paniculata (Orange jassmine), one of the host plants. D.citri may be able to survive in winter season due to global warming in near future (Fig. 6).

POTENTIAL IMPACT OF GLOBAL WARMING ON FRUIT TREES

Sugiura et al. (2004) showed the impact of global warming on the production in Japan of apples and Satsuma mandarins. The annual mean temperature was used to simulate possible changes in favorable regions for the cultivation of apples and Satsuma mandarins. The temperature ranges assumed to be appropriate for fruit production were 6-14ºC for apples and 15-18ºC for Satsuma mandarins, respectively.

It was predicted that the favorable regions to cultivate apples and Satsuma mandarins will gradually move northward. In the 2060s, the plains of central Tohoku has been predicted to be unfavorable for apple cultivation, while most of Hokkaido will be suitable (Fig. 7). The plains of northern Tohoku are predicted to attain the annual mean temperatures higher than those of the current main producing districts. By 2060s, the favorable areas for Satsuma mandarin production will possibly move from the southern coastal sites to inland areas of western and southern Japan, the plains of Kanto and the littoral zones of the Japan Sea in the central and western Japan and in southern Tohoku.

ADAPTATION TECHNIQUES OF FRUIT TREES

Coloring disorder is one of the most serious problems in fruits. For apples, technological counter-measures include a switch to varieties with excellent coloring properties and techniques to increase the amount of sunlight through reflective mulches and other techniques. There are techniques to enhance the coloration of grapes through girdling. With the grapevine girdled, sugars photosynthesized in the leaves accumulate in the branches and leaves. As a result, the sugar content increases in the upper part from the girdled portion at the time of harvesting, which in turn promotes the synthesis of anthocyanin and enhances the coloration. Recent studies show that the coloration can be further enhanced with girdling and the absence of bagging. Other coloration enhancement techniques include abscisic acid treatment and optimization of the number of fruits per tree (Fig. 8).

For disorder of budding of pears under greenhouses, it has been found that this is caused by high temperatures during autumn and winter. This phenomenon can be prevented by spraying cyanamide or by starting the heating process after being exposed to adequate low temperature. Fog cooling is based on the conversion of sensible heat to latent heat through the evaporation of water droplets sprayed over the air inside the greenhouse.

Silver mulch treatment is not a method for improving temperature, but for improvement of refracted light condition to fruits. This technique is practically used, and although control (without mulch) was not shown, silver mulch could improve skin coloration.

This plastic mulching with drip irrigation system has high adaptability against climate change in both climate conditions of much rainfall (by plastic mulching) and dry season (by drip irrigation). This system had been introduced in major citrus producing areas in western Japan such as Wakayama, Kagawa and Ehime in recent years. High fruit quality and productivity has been maintained in these areas (Fig 9).

RECENT EFFECTS OF GLOBAL WARMING AND ADAPTATION TECHNIQUES OF VEGETABLES

In vegetable crops, disorder of eggplants such as bad bearing and growth, are also caused by high temperatures (Fig. 10). In addition, decrease of yield by fruit drop, low fruit quality, and malformed fruits are serious problems in Japan. In strawberry greenhouses, momentary pause of harvest, low harvest, malformed fruit, low fruit quality are caused by the exposure of high temperature after transplant.

Several effective breeding materials of eggplant such as AE-P strains have been developed. These materials have parthenocarpy under high temperature. It is expected that superior varieties which have high bearing rate under global warming condition will be bred in the future.

Greenhouse cultivation system of vegetables has been developed for the past three decades in Japan. Nowadays, year-round production and shipping of vegetables have been established. However, recent air temperature in summer exceeds the optimal range. Productivity and quality of several main vegetables such as tomato, strawberry, spinach under greenhouse condition have decreased during high temperature period caused by global warming. Several control techniques such as ventilation, shading, fog cooling and heat pump have been researched to improve environmental condition. Photo-selective films have been tried to prevent severe sunlight and change spectral quality in greenhouses. Recently, a new fog cooling method with twin-fluid nozzle type has been introduced and tested to keep optimal temperature in greenhouses.

A new modified elevated bed system of strawberry through culture medium cooling using vaporization heat has also been developed in greenhouses. This system has the cooling effect of culture medium by 3ºC lower than that of the existing system.

STRATEGY ON GLOBAL WARMING

As global warming is considered inevitable, there is a need to continue studying mitigation measures (techniques to reduce greenhouse gas emissions from agriculture, forestry and fisheries) and, as discussed in this report, adaptation techniques. MAFF (Ministry of Agriculture, Forestry and Fisheries) of Japan, therefore, announced the "Integrated Strategy for Global Warming" in 2007.

The following activities are emphasized in the "Studies on Global Warming Countermeasures" with focus on mitigation, adaptation and impact assessment. As immediate measures of adaptation, heat-resistant varietiesthat meet the needs of growers and techniques that ensure stable agricultural production are being developed. In addition, a more accurate assessment is needed for the nature, degree and period of the impact of global warming on agriculture. The results of this assessment will then serve as the basis for studying adaptation measures including cropping conversion.

There are short and middle-long term targets in Japan. The short-term targets consist of: 1) development of countermeasure techniques for present disorders and damages such as abnormal ripening and less coloration; 2) chemical control of bad sprouting of Japanese pear and peel puffing of Satsuma mandarins; 3) temperature control in orchards and greenhouses; and 4) replanting to present varieties adaptable to high temperature. The middle-long term targets consist of: 1)clarification of mechanism of high temperature on growth of fruit and plants; 2)gene expression analysis under high temperature such as MdMYBA; 3)analysis of relationship between high temperature and quality etc.; 4)breeding program of new varieties and techniques which have higher adaptability to global warming than present status.

CONCLUSION

The IPCC 4th Assessment Report showed that contribution of agriculture to the total GHG emissions in the World is 10-12 %. It is important to research in order to reduce GHG emissions from agricultural industry. Japan aims to reduce 25% CO2 emission by 2025. In addition to mitigation approaches and techniques, the practical approaches against present negative impacts of global warming have been important to maintain agriculture and food production, and the elucidation of the mechanisms of effects on high temperature could also be important to its efficient development. Both practical and basic studies on horticultural crops and other crops as well should further be studied to overcome the problems caused by global warming.

REFERENCES

  • Ashihara, W. (2006): Present research on citrus greening disease and distribution of Diaphorina citri (citrus psylla). Syokubutu Boeki 60(7) 291-294.
  • Japan Meteorological Agency (2010): Climate change
  • http://www.data.kishou.go.jp/climate/cpdinfo/climate_change/index.html
  • IPCC (2007): Observations: surface and atmospheric climate change, Fourth Assessment Report: http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter3.pdf
  • IPCC (2007): Regional Climate Projections, Fourth Assessment Report:
  • http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter11.pdf
  • Iwanami, T. (2009): Counterstrategy of controlling citrus greening disease associated with global warming. NARO International Symposium on Impact of global warming on food and agriculture -Frontiers of developing technological countermeasures- 65-70.
  • Kikuchi, K. (2007): Fruit set of parthenocarpy eggplants under high temperature condition. Abstract of Research Meeting on Climate Change. edit NIFTS, 26-27.
  • Kondo, M. (2009): Effect of high temperature on rice with focus on grain quality and carbon dynamics. NARO International Symposium, on Impact of global warming on food and agriculture -Frontiers of developing technological countermeasures- 49-51.
  • Lee, DB, Shim KM and Rho KA (2009): Strategy on enhancing adaptation to climate change using agro-ecosystem. 2009 International Symposium _ Strategies for agricultural adaptation to climate change.73-80
  • Ministry of Agriculture, Forestry an fisheries (2003): Impact of Global warming on agriculture, forestry and fisheries and possible countermeasures in Japan. Report on research and development in Agriculture, Forestry and Fisheries No.23.
  • Moriguch, T. (2009): Recent advances in overcoming endodormancy breaking dysfunction and less coloration in deciduous fruit trees under global warming conditions. NARO International Symposium, on Impact of global warming on food and agriculture -Frontiers of developing technological countermeasures- 61-63.
  • Morinaga, K., S.Nakao, O.Sumikawa and O.Kawamoto (2005): New technologies and systems for high quality citrus fruit production, labor-saving and orchard conservation in mountain areas of Japan. Proceedings of the International Society of Citriculture. 1204-1208.
  • Sugiura, T. (2009): What become of `Agriculture' and `Food' by Global Warming? Gijyutu-hyoronsya, Tokyo, Japan.
  • Sugiura, S. and M.Yokozawa (2004): Impact of global warming on environment for apple and Satsuma mandarin production estimated from change of the annual mean temperature J. Japan. Soc. Sci., 73(1):72-78.
  • Yamane, S. and K.Shibayama (2006): Effects of trunk girdling and crop load levels on fruit quality an root elongation in `Aki Queen' grape berries. J.Japan, Soc. Hort.Sci. 75:458-462.


Index of Images

  • Fig. 1 Global mean temperature and Japan's mean temperature since 1890s.

    Fig. 1 Global mean temperature and Japan's mean temperature since 1890s.

  • Fig. 2 Global mean temperature over the last 150 years

    Fig. 2 Global mean temperature over the last 150 years

  • Fig. 3 A survey on the effect of global warming on agricultural industry in Japan

    Fig. 3 A survey on the effect of global warming on agricultural industry in Japan

  • Fig. 4 Skin color disorder of grapes (Yamane 2006) and apples

    Fig. 4 Skin color disorder of grapes (Yamane 2006) and apples

  • Fig. 5 Budding disorder of Japanese pear by recent warming (Sugiura 2009)<BR>

    Fig. 5 Budding disorder of Japanese pear by recent warming (Sugiura 2009)

  • Fig. 6 Distribution map of citrus greening disease (HLB), Diaphorina citri (citrus psylla) and Murraya paniculata (Orange jassmine) in Japan (Ashihara 2006)<BR>

    Fig. 6 Distribution map of citrus greening disease (HLB), Diaphorina citri (citrus psylla) and Murraya paniculata (Orange jassmine) in Japan (Ashihara 2006)

  • Fig. 7 Potential impact of global warming on fruit production - The favorable

    Fig. 7 Potential impact of global warming on fruit production - The favorable

  • Fig. 8 Improvement of skin color in grapes by girdling and appropriate fruit load

    Fig. 8 Improvement of skin color in grapes by girdling and appropriate fruit load

  • Fig. 9 Improvement of fruit quality by control of water status using plastic mulching and drip irrigation (fertigation) in citrus orchard

    Fig. 9 Improvement of fruit quality by control of water status using plastic mulching and drip irrigation (fertigation) in citrus orchard

  • Fig. 10 Disorders of eggplant fruit

    Fig. 10 Disorders of eggplant fruit

  • Table 1 The percentage of indication of phenological changes by recent warming

    Table 1 The percentage of indication of phenological changes by recent warming

  • Table 2 The percentage of indication of changes on fruit quality by recent warming

    Table 2 The percentage of indication of changes on fruit quality by recent warming

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