本文試著從原住民的傳統山林經驗與官方的山區開發，來討論南部山區「昔日鬱鬱，今之濯濯」之成因，文中分別從幾個部分加以探討：原住民口述傳說中的天然災害經驗、原住民的傳統山林經驗、邊區移民以及原住民聚落、日治時期的製腦業與腦區、戰後南部山區的林野開發。文中希望從原住民的傳統文化中，對於天災的口述傳說經驗，瞭解其對於天災的經驗傳承與避難態度。接著討論原住民其傳統的山林燒墾，是否會對自然造成嚴重的破壞，而究其原因乃是官方為了行政管理與山區開發之故，絕非濫伐之因。然而文中也初步討論六龜一帶的「防蕃性」聚落的形成，由於位置與往後森林砍伐關係，目前都是土石流橫行之處，其原居地應該不會是如此狀況；現今，其它的原住民聚落，也是在官方的「集團移住」政策下，被移到現址，依然是土石流警戒之處。 此文另一個討論的重點，在於釐清南部山區樟腦、大規模伐木事業的發展梗概，因此初步整理出樟腦製腦地與伐木單位承繼關係，試著把天然災害的產生，導向人為砍伐森林的思考，不過針對天然災害成因的分析是複雜且複合成因，礙於篇幅，並未再深究。 文末，希望「昔日鬱鬱，今之濯濯」的森林外貌，能在後人的努力下，還給大自然一個原始的自然空間，也對於原住民傳統山林生態經驗與智慧，給予應有的尊重與肯定。

The paper discusses causes of changes from hills with dense forest in ancient times to treeless hills nowadays via forest cultivation between aborigines and the government. The paper is composed of five parts, including natural disasters from aboriginal narratives, traditional mountain experiences of aborigines, immigrants in the border areas and aboriginal settlements, camphor industry and plantation in the Japanese colonial period, and forest and wild land development in southern mountain areas after the 1945. The paper aims to clarify aboriginals’ traditional experiences and evacuation methods toward natural disasters. The paper further discusses the relationship between aboriginals’ traditional slash-and-burn cultivation on forests and natural resource damage. The paper approves the deforestation is necessary for easy administration and development on mountain areas by the government. The paper also talks about formation of the settlements built to defend aborigines in Liouguei Township. Due to geographic location and deforestation, the settlements are suffered from mud floods and become dangerous areas. The present other aboriginal settlements were formed by governmental group immigration, and suffered by mud floods now. The other key point of the paper is to find out the developing history of camphor and large-scale deforestation industries. The relationship between camphor production in southern mountain areas and deforestation units is investigated based on human causes. The natural causes are too complex to discuss in this paper. We hope to call back primitive natural land by environmental care and efforts, and endow aborigines with respect and affirmation on their traditional mountain experiences and wisdom.