氣候變遷與糧食生產

Climate Change and Food Security

楊純明(Chwen-Ming Yang)

《作物、環境與生物資訊》 6卷2期 (2009/06) Pp. 134-140

https://doi.org/10.30061/CEB.200906.0006

摘要

全球之「氣候變遷(climate change)」現象為一極端複雜之議題，不僅反應地表平均氣溫(mean global air temperature; MGAT)的上升，亦牽涉整個空氣層大氣系統的綜合變化，由於其涵蓋地球上的每一個角落，因而成為眾所矚目的焦點。關於氣候變遷的主因，目前已廣泛地被歸諸於自工業革命以來長期溫室氣體(greenhouse gases; GHGs)累增所造成全球溫暖化而衍生的一項結果。這些溫室氣體（或稱溫室效應氣體greenhouse-effective gases）雖然微量（相較於佔有高達空氣組成78%以上的氮氣及幾近21%的氧氣），卻能夠有效地截取地表放射至外太空的長波輻射（特別是紅外光波段），因此部分保存了原來預定於夜間外釋的地表輻射能，破壞了地表的日夜能量平衡。另一方面，諸如二氧化碳(carbon dioxide; CO2)、甲烷(methane;CH4)、氧化亞氮(nitrous oxide; N2O)及氟氯碳化物(chlorofluorocarbons; CFCs)等溫室氣體，又會減少大氣對流層中有利的臭氧濃度，使得大氣的臭氧層稀薄而增加紫外線照射至地表的入射量。據估計過去的百年期間，MGAT 上升了1.3-4.5℃，倘若維持現行遞增速率，推估至2100 年MGAT 將上升1.4-5.8℃ (IPCC 2001a, 2007)。地表氣溫上升將產生許多環境(environment)乃至於經濟社會問題(socio-economic consequences)，並因此為農、林、漁、牧各產業帶來深遠影響，也對人體健康及生物多樣性等造成相當衝擊。在可預見氣候變遷持續進行趨勢下，頻率升高的天然災變(natural disasters)及極端天氣事件(extreme weather events)將嚴重威脅人類生活與生存，並造成民眾日常活動的不便，更將形成糧食供需失調。放眼未來人口增長而糧食供給短缺的可能性，氣候變遷現象被預期將陷數以百萬計民眾於饑餓風險，更將引發另一項重要的「糧食安全(foodsecurity)」議題，使得氣候變遷與糧食安全兩項議題密不可分。農林產業本身可以緩解氣候變遷負面趨勢，例如造林、復林及採行改良的農地與牲畜管理等措施，即可助益於減少溫室氣體的排放或濃度。又綜合各項科學數據及事實，氣候變遷給全球帶來了全面性的衝擊，尤以亞非地區(Afro- Asian region)的國家受到的影響最為明顯。為期克服氣候變遷及糧食安全相關的各種問題，以及所引發的各項挑戰，國際社會應當團結一致謀求解決之道，並提供受害較大國家必要的援助與協助。國內部分依照中央氣象局的統計資料，臺灣的氣溫在過去一百年(1901-2001)期間上升了約1.3℃，其特色是增溫幅度夏季高於冬季、夜晚大於白天。由於可預見的未來國內仍將朝著都市化(urbanization)與工業化(industrialization)方向發展，溫暖化的趨勢將無法避免。臺灣周遭區域將持續籠罩溫暖化氣候，預期會有更加乾燥的冬天和潮濕的夏天。建議政府各部門宜針對氣候變遷與糧食安全相關議(問)題進行長期研究探討，隨時提出因應對策。而在緩解(mitigation)與調適(adaptation)作法上，宜建構配套式系統性政策與措施，才能有效解決問題的根源讓國家長治久安。

關鍵字

氣候變遷 ； 糧食安全 ； 溫室氣體 ； 緩解作法 ； 調適作法

並列摘要

Global climate change (CC) is a very complex issue referring not only to an increase in the mean global air temperature (MGAT) but to an integrated system of atmospheric phenomena covering over a large scale of the world. The main cause of this global concern is widely acknowledged attributing to a long-term warming trend owing to the increase of greenhouse gases (GHGs) such as carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and chlorofluorocarbons (CFCs) since the onset of the industrial revolution. These trace gases lead to warming the air temperature by trapping the energy from the outgoing longwave radiation (terrestrial radiation) and may also alleviate the beneficial ozone layer present in the stratosphere. An increase in MGAT in the range of 1.3-4.5℃ is estimated during the past century, and is projected to rise from 1.4℃ to 5.8℃ by the year 2100 (IPCC 2001a, 2007). The increasing MGAT will impose a variety of environmental and socio-economic consequences which in turn would exert profound influences on agriculture, forestry, fishery and livestock and have an impact on human health and bio-diversity. On the trend of CC, natural disasters and extreme weather events will be a serious threat to human survival and activities due to growing imbalances in demand and supply of foods. With the predicted rise in world's population and short of food supply, climate change is expected to put millions of people at risk of hunger and bring forth the importance of food security issue. Agriculture and forestry can play a role in solving problems emerged from climate change through the practices of afforestation, reforestation, and better land and livestock managements. The scientific facts suggest that the impacts of climate change are expected to affect all the countries of global village, especially the countries of Afro-Asian region. To overcome the challenges of climate change and food security issues, the international community should act as a whole with concerted endeavors in providing the needed helps to the suffering countries. In case of Taiwan, the weather statistics declared by the Central Weather Bureau indicated that there was an increase of 1.3℃ in average air temperature in the time period from 1901 to 2001, nearly two-fold of mean MGAT. The increment was higher in summer seasons than in winter months and the increase of nighttime temperature was larger than that of the daytime temperature. With the continue urbanization and industrialization trends, it is very likely that the warming rate will increase in the future to come. The projected warming climate will accompany with a dry winter and humid summer. To mitigate and adapt to the effects of climate change on food security and challenges faced in the present and the future, the government of Taiwan ROC is suggested to take the systematic measures and action plans to solve the problem evolved.

並列關鍵字

Climate change ； Food security ； Greenhouse gas ； Mitigation measure ； Adaptation measure