基于信息网络模型的生态风险评价

人类开发活动造成剧烈的生态系统自然条件变化,生态风险评价可以对受到人为干扰下生态系统(包括物种和群落等)的潜在影响进行模拟和量化。通过对信息流量的概念和网络控制分析,综合考虑生态系统组分间的直接和间接作用,提出一种能实现全局风险模拟的生态网络模型,即信息网络模型。在该模型基础上,建立了面向整体生态系统的生态风险评价框架,同时实现兼容多胁迫因子统一模拟和多风险受体间的风险追踪。以澜沧江漫湾水库为例,在估算重金属Hg、Pb和Cd初始环境风险后,利用信息网络模型追踪分析生态系统中不同生态功能组分之间的风险传递路径,评估各生态组分和整体系统的危险程度。结果表明,在累积效应作用下,对于生态系统和部分群落,整合网络风险值与初始环境风险值之间有着显著差别;在发生环境胁迫时,虽然处于食物网底层的生物类群可能最先受险,但在控制信息作用下食物网上层类群也会受险,甚至其最终受到的潜在威胁比前者更大。信息网络模型可识别出复杂的风险流动路径和群落间的风险累积,从而为生态系统风险评价和管理提供更为系统综合的理论依据。

Ecological risk assessment based on information network model

The natural properties of ecosystems have been widely altered by human activities, which in turn cause the endangerment of a range of species that will eventually affects humanity. Ecological risk assessment (ERA) is capable of modelling and quantifying the potential impact on ecosystems and their components (such as species and communities) initiated by human disturbance. In this study, a conceptual conversion of flow currency in network was accomplished, i.e. from the material/energy flow to the information flow. Based on the introduction of control allocation analysis and the estimation of the components'' sensitivities to the stressor, we developed a new type of network analysis for holistic ecological risk assessment, so-called information-based network model. The reservoir ecosystem intercepted by Manwan Dam was used as a case study, The initial environmental risks were calculated based on the changes of three heavy metals (Hg, Pb and Cd), and the propagation of resultant risk between all functional components of the ecosystem was tracked. By incorporating both direct and indirect ecosystem interactions, the risk conditions of the whole ecosystem and its components were quantified and illustrated in the information networks. The results showed that: (1) on both ecosystem level and component level, there were significant differences between integral risk and initial risk after disturbance due to network amplification effect; (2) Hg seemed to cause the most highest integral risk to the ecosystem among the three heavy metals (3) almost all components had multiple sources of risk rather than solely received from the original input source (except the absolute controller, who only gives off risks but never receive one from other components); (4) the number of risk flow pathways notably increased from the input situation to network direct situation and to integral situation, implicating that the dynamics of the ecosystem are better manifested through a network perspective.