日本沿岸種下 68 萬棵樹，森林防災能否補足海堤限制

日本東北沿岸的 Chinju no Mori 計畫 14 年來種植約 68 萬棵樹，嘗試以原生森林帶配合海堤降低海嘯衝擊。近期在南相馬市，約 1,000 名志工再種下 12,000 棵。

The Chinju no Mori initiative has planted about 680,000 trees along northeastern Japan over 14 years, using native coastal forest to complement seawalls. About 1,000 volunteers recently planted another 12,000 trees in Minamisoma.

2011 年規模 9.0 地震及海嘯造成超過 19,700 人死亡。災後日本大規模興建海堤，同時出現以森林作為第二道緩衝的混合防災設計。

The magnitude 9.0 earthquake and tsunami of 2011 killed more than 19,700 people. Japan built extensive seawalls after the disaster while some communities added forests as a second buffer.

森林無法阻擋所有海嘯，樹齡、密度、地形與波高都會改變效果。宮脇式密植的生態效益也有研究爭議，因此不能把植樹數量直接當成安全成果。

Forests cannot stop every tsunami, and performance depends on tree age, density, terrain and wave height. Evidence around dense Miyawaki planting is also contested, so tree counts cannot be treated as safety outcomes.

計畫採用在地樹種及密植方法，將植栽設於海堤後方或堤體附近。合理做法是把森林、工程設施、疏散路線、土地使用與預警系統視為一套多層防線。

The project uses locally native species and dense planting near or behind seawalls. A robust approach treats forests, engineered structures, evacuation routes, land use and warning systems as a layered defence.

68 萬棵、14 年與南相馬活動數字來自報導。研究顯示高於 5 公尺的海堤通常能降低損害，較小海堤在某些情況可能增加風險；森林較適合緩衝較小事件。

The 680,000 trees, 14-year period and Minamisoma event come from reporting. Research indicates seawalls above five metres generally reduce damage, while smaller walls can sometimes increase risk and forests are better suited to smaller events.

自然為本解方可提供生態與社區共同效益，但必須清楚界定其防護上限。錯誤的安全感可能鼓勵高風險地區重新開發。

Nature-based solutions can deliver ecological and community benefits, but their protection limits must be explicit. A false sense of security can encourage redevelopment in high-risk areas.

SNN 編輯分析：防災專案需要追蹤的不只是種植量，還包括存活率、林帶結構、模擬情境、疏散時間與災後損害，才能形成可驗證韌性證據。

SNN editorial analysis: Resilience evidence should track survival rates, forest structure, modelled scenarios, evacuation time and post-event damage, not planting totals alone.

後續應比較不同植樹方法的長期存活與生態結果，並透過模型與實際事件檢驗森林和海堤的組合效果。

Further work should compare long-term survival and ecological outcomes across planting methods and test combined forest and seawall performance through models and real events.