Future restoration should enhance ecological complexity and emergent properties at multiple scales

Ecological restoration has a paradigm of re-establishing 'indigenous reference' communities. One resulting concern is that focussing on target communities may not necessarily create systems which function at a high level or are resilient in the face of ongoing global change. Ecological complexity - defined here, based on theory, as the number of components in a system and the number of connections among them - provides a complementary aim, which can be measured directly and has several advantages. Ecological complexity encompasses key ecosystem variables including structural heterogeneity, trophic interactions and functional diversity. Ecological complexity can also be assessed at the landscape scale, with metrics including beta diversity, heterogeneity among habitat patches and connectivity. Thus, complexity applies, and can be measured, at multiple scales. Importantly, complexity is linked to system emergent properties, e.g. ecosystem functions and resilience, and there is evidence that both are enhanced by complexity. We suggest that restoration ecology should consider a new paradigm to restore complexity at multiple scales, in particular of individual ecosystems and across landscapes. A complexity approach can make use of certain current restoration methods but also encompass newer concepts such as rewilding. Indeed, a complexity goal might in many cases best be achieved by interventionist restoration methods. Incorporating complexity into restoration policies could be quite straightforward. Related aims such as enhancing ecosystem services and ecological resilience are to the fore in initiatives such as the Sustainable Development Goals and the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services. Implementation in policy and practice will need the development of complexity metrics that can be applied at both local and regional scales. Ultimately, the adoption of an ecological complexity paradigm will be based on an acceptance that the ongoing and unprecedented global environmental change requires new ways of doing restoration that is fit for the future.

生态恢复有一种重建“本地参照”群落的范式。由此产生的一个担忧是，关注目标群落不一定能创建出在高水平上发挥功能或在持续的全球变化面前具有恢复力的系统。生态复杂性——在此根据理论定义为一个系统中的组成部分数量以及它们之间的连接数量——提供了一个补充性目标，它可以直接测量且具有若干优势。生态复杂性涵盖关键的生态系统变量，包括结构异质性、营养相互作用和功能多样性。生态复杂性也可以在景观尺度上进行评估，衡量指标包括β多样性、栖息地斑块之间的异质性和连通性。因此，复杂性适用于多个尺度且可以在这些尺度上进行测量。重要的是，复杂性与系统的涌现特性相关联，例如生态系统功能和恢复力，并且有证据表明复杂性可增强这两者。我们建议恢复生态学应考虑一种新范式，以在多个尺度上恢复复杂性，特别是在单个生态系统以及整个景观中。复杂性方法可以利用某些当前的恢复方法，但也涵盖诸如再野化等较新的概念。实际上，在许多情况下，通过干预性恢复方法可能最能实现复杂性目标。将复杂性纳入恢复政策可能相当简单。诸如增强生态系统服务和生态恢复力等相关目标在可持续发展目标以及生物多样性和生态系统服务政府间科学政策平台等倡议中处于重要地位。在政策和实践中的实施将需要制定可在地方和区域尺度上应用的复杂性指标。最终，生态复杂性范式的采用将基于这样一种认识，即持续且前所未有的全球环境变化需要适合未来的新的恢复方式。