当人们对一些经典概念和模式，如经济最优化模式、生态最适模式、最低安全标准、承载力概念等提出疑问之后，环境与发展规划的方法论也随之面临着严峻的挑战。本文指出：①以经济最优化和生态最适模式指导规划都是非常局限和困难的，规划决不是一个环境和经济决定论的过程，而是一个可辩护的过程；②环境可能会对发展产生所谓的“顶极的”“绝对的”制约，对此，规划必须服从。但是，这种“顶极的”和“绝对的”界线是很难确切定义的，也往往是难以操作的，因而其在环境与发展规划中的意义是相当有限的。必须寻找一些新的有效的战略使规划过程具有可辩护性和可操作性。如何寻求和设计这种辩护战略是可持续发展规划方法论的一个重要领域。生态安全格局途径正是在这一方向上所做的努力。

The methodologies of environmental and development planning have been severely challenged when classic concepts and models such as economic optimum,ecological fitness,safe minimum standard,carrying capacity,and even sustainability have been questioned. It is observed that:(a) it is extremely difficult to have the planning aimed at being either ecological or economic optimum,i e. planning is not a process determined absolutely in terms of environmental and economic criteria,but rather a defensible one (b) there are some“ultimate ”or “absolute”constraints,which the planning has to come to terms with,but these constraints are hardly definable or acceptable. Therefore,they play a quite limited role in the practice of environmental and development planning. What is urgent is to find some new and effective make the planning process both defensible and operational. As to how to find and design such a defensible strategy serves as an essential field concerning methodologies for sustainable development planning The security pattern approach in planning is an attempt in this direction.