湿地功能快速评价中的若干理论问题

Discussion on Some Problems of Rapid Assessment of Wetland Function

针对目前湿地功能快速评价中存在的不足之处,分析了产生这些不足的原因及湿地功能快速评价过程中存在的一些基本理论问题。分析表明:湿地功能快速评价方法是为了达到“湿地功能无净损失”目的,是在需要评价的湿地如此之多而从事湿地功能评价的专业人员又极其缺乏的情况下发展起来的。它对于湿地恢复与重建以及湿地受人类活动干扰程度的评价是非常有效的;在湿地功能快速评价过程中,把相对未受人类干扰的参照湿地的功能指数规定为1,这就使得快速评价方法不能对参照湿地的功能进行评价,而目前最需要评价其功能的湿地往往就是这些相对未受人类活动干扰的湿地;在相同水文地貌的湿地类型内评价湿地功能之间的差异,这使得快速评价方法不能评价湿地的水文地貌功能;由于快速评价的结果都是相对的功能指数,并不能说明湿地所提供的功能量是否满足人们的需求,因而在决策中不能单独使用;快速评价都是“一次调查就获得结果”,同时由于快速评价过程中指标选择的主观性、指标赋值的主观性、采样点空间设置的主观性以及采样时间的主观性,对于具有时空变化特征的湿地功能的评价结果的可重复性和科学性是很低的。为了使湿地功能评价的结果对管理和决策具有指导意义,基于湿地功能量计算的、定量的评价湿地功能的方法必须开发出来。针对不同的评价目的,湿地功能评价可采用双重参照标准:一是以自然为参照来评价湿地功能受人类活动影响的程度以及湿地恢复与重建成功与否;二是以人类需要为标准来评价湿地提供的功能量是否满足了我们的期望,以便采取措施改进湿地功能来满足人类的需求。

Wetland function assessment focuses on the development of rapid assessment methods at present, but there are many disadvantages in the methodology and results of rapid assessment methods. Aiming at overcoming these disadvantages, the paper analyzed intensively the causes resulting in the disadvantages and some theoretical problems in the process of rapid assessment. The analysis results indicated that rapid assessment methods for wetland functions were based on ＂not net function loss＂ policy and under the condition that there were so many wetlands need to assess and there were just a few professional assessors available. It is a useful tool to assess the success of wetland restoration and the degree of human disturbance to wetlands, but there are some wetland classes or subclasses and some types of wetland functions can not be assessed by rapid assessment methods. In the process of rapid assessment of wetland functions, the function index of reference wetlands, which are always natural wetlands or wetlands less disturbed by human action, are always evaluated the value 1. Doing this makes it impossible to assess the functions of natural wetlands, but they are always natural wetlands or wetlands less disturbed that need to be assessed imperatively. Rapid assessment methods can not assess the hydrogeomorphic function because function assessment is always restricted in the same hydrogeographic wetland category. The resuit, of rapid assessment, i.e. the function index, can not show if the function capacity provided by certain wetland satisfies our requirement, therefore, it can not be used to direct decision -making alone. Because the assessment result is acquired at one field visit and because of the subjectivities in assessment process, such as the subjectivities of indicator selecting, indicator evaluating, and sampling site locating and sample timing, the assessment result is unrepeatable and its accuracy and scientificity are always low. Aiming at overcoming the disadvantages of rapid assessment methods, it is necessary to develop quantitative methods for wetland function assessment based on function calculating. In allusion to different assessment purpose, reference standards for wetlands function assessment should adopt the following two criteria： ①taking natural wetlands as reference wetlands to assess the disturbance degree by human influence and the success of wetland restoration and mitigation; ②taking human requirement as reference criteria to assess if the function capacity of certain wetland satisfies our expectation, so that some measures can be carried out to improve wetland functions.