人类经济的发展从来就是用相对丰富的资源替代相对稀缺的资源。从采集渔猎，到刀耕火种，最后进入永久农业的过程，从经济学角度分析就是在技术不断更新下人造资本取代自然资本的过程。历史上一直是原始林被次生林和农地取代，只是在近百年来，许多国家和地区相继出现林地取代农地的现象。人工林也成为木材生产的主要来源，同时还相继出现许多专门为人类提供生态服务的森林。森林变迁主要原因是农业技术革新和人口变化导致农产品、林产品以及森林资源生态服务的相对价值变化的结果。本文用美国、新西兰以及中国的海南岛为例来验证这一原理，从经济学的角度提出对未来森林生态系统的展望。
Expansion or contraction of forest ecosystems on the earth has been driven by the changes in relative scarcity of the products and services from the lands．For a long history worldwide，food has been relatively scarcer than wood，so forests have been largely changed into agricultural uses．However，due to the dramatic decrease of forests in the world during the last century，wood products as well as forest ecological services are becoming relatively scarcer than food and therefore many agricultural lands have been converted back into forestlands．Meanwhile．Plantations have replaced natural forests as a major timber supply in most countries．This paper first briefly explains the evolution of forest land use/cover from economics perspective，then uses land use changes in the US，New Zealand and the Hainan Island of China as examples to support our argument．Finally a perspective of the future forestland change is presented based on the principles of economics．
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