Beyond carbon storage: the Congo Basin forest as rainmaker
文 / Denis Sonwa (世界森林研究中心, Center for International Forestry Research, CIFOR)
譯 / 人禾環境倫理發展基金會
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| 剛果盆地的毀林將會使降雨的循環過程被中斷而影響氣候改變。 |
氣候變遷的因應，常常會被分成兩個主要議題：減量(減少溫室氣體排放)與適應(調整生計跟生活方式來影響氣候變遷)。其中適應的策略包括，以生態系為基礎的調適(ecosystem-based adaptation, EBA)，這是一個透過對利用自然資源跟生物多樣性的促進，來協助脆弱的社區發展適應性策略的途徑。在這樣的考量下，剛果盆地的森林在關於調節降雨的研究中，扮演著有亮眼的角色。
Responses to climate change are grouped into two main categories: mitigation (reducing greenhouse gas emissions responsible for climate change) and adaptation (adjusting livelihoods and life styles due to the influences of climate change). Amongst adaptation strategies, ecosystem-based adaptation (EBA) is an approach that promotes ways to use natural resources and biodiversity to help develop adaptation strategies for vulnerable communities. In this context, recent studies highlight the role that the Congo Basin forests play in generating rainfall, both regionally and in the continent as a whole.
生態系中降雨通常來自三個主要來源：在大氣中原本就含有的水氣、從其他地方來的水氣，以及生態系表面的蒸散作用(包含森林或其他土地利用)。Pokam等人研究發現剛果盆地的氣候主要被大西洋的水氣跟蒸散作用的循環過程影響。研究發現：像是剛果盆地一樣的熱帶雨林，每年可以蒸散1到2公尺的水。此外，Makarieva等人的研究也說明有森林覆蓋的表面就像是有一個幫浦，讓海洋朝向大陸的濕氣最後會變成在這個地區的降雨。
Rainfall in an ecosystem originates from three main sources: moisture that is already in the atmosphere, moisture from outside the region, and evapotranspiration from surfaces within the ecosystem (forests and other land uses). Pokam et al. studied how the climate of the Congo Basin is primarily a result of moisture from the Atlantic Ocean and the recycling process of evapotranspiration. Previous studies had established that tropical forests such as the Congo Basin can evaporate up to 1 to 2 meters of water per year. In addition, research by Makarieva et al. suggests that forest cover in the region acts like a pump, moving oceanic moisture towards the continent to eventually become rainfall in that region.
森林的角色就像是降雨的產生者。Nogherotto等人在這樣的概念下發現，在剛果盆地因為毀林對於地區水循環產生的衝擊，這些衝擊包含非洲季風所帶來的影響。他們模擬了剛果盆地有森林跟沒有森林(將森林改成草地)的情況，指出剛果盆地的毀林確實會改變沙哈拉地區(Sahel)跟赤道南邊的非洲的降雨現象。
With this role of forests as rainmakers in mind, Nogherotto et al. explored the impacts of deforestation in the Congo Basin on regional hydrological cycles, including the effects on the African monsoon. They modeled scenarios where the Congo Basin is forested versus those in which it is deforested (that is, modeling a situation where forest cover is transformed to short grass cover). Their findings indicate that deforestation in the Congo Basin would lead to modifications in rain behavior in the Sahel and over southern equatorial Africa.
整合這三個研究，可以得知剛果盆地如何像是一個幫浦將大西洋的水氣從地下水跟土壤帶向陸地。這些水氣最後會跟大氣中的水混合在一起，最後產生地區性以及次大陸規模的降雨。假如剛果盆地沒有森林覆蓋的話，這樣的過程可能會被嚴重中斷。此外，這些研究也突顯剛果盆地森林的其他重要功能，包括生物多樣性保育跟溫室氣體減量能。
Taken together, these three studies show how the Congo Basin acts as a mechanism for pumping water from the Atlantic Ocean, from underground sources, and from the soil. These sources then mix with atmospheric water, leading to the generation of rainfall both locally and on a sub-continental scale. Without the extensive forests of the Congo Basin, this process would be severely disrupted. In addition, these studies help highlight other important functions of the Congo Basin forests beyond biodiversity conservation and climate change mitigation.
越來越多的科學證據證明剛果盆地的森林在地區、大陸跟全球的規模都扮演了多重角色。這對於森林保育、森林經營管理以及多種收入來源支持森林的各種角色的案例就變得更具說服力。維持剛果盆地森林的降雨功能，將會是討論非洲的生態系在氣候變遷調適上的重要基礎。
With the growing scientific evidence of the multiple roles that the Congo Basin forests play at regional, continental and global scales, the case for forest conservation, for good forest management, and for multiple income streams to support the forests’ multiple roles becomes stronger. Given their rainmaker role, sustaining the Congo Basin forests might be one of the foundations for EBA to climate change for much of Africa.
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