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

Abstract

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 themprovides 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 β 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.

Supporting the restoration of complex ecosystems requires long‐term and multi‐scale perspectives

“…This is well aligned with the general framework for rewilding proposed by Perino et al (2019), which argues for restoration along trophic complexity, dispersal/connectivity and stochastic ecosystem disturbances, and the interactions between these ecological processes. In particular, this points towards the importance of recovering keystone species that promote the trophic complexity (in line with the trophic rewilding concept defined in Svenning et al 2016), the functional integrity and the ecological resilience of ecosystems, similarly highlighted in Bullock et al (2021). Rewilding can thus be seen sitting with a broader framework of restoration aiming at restoring ecologically complex ecosystems to promote functional integrity and resilience and higher landscape-scale biodiversity (Fernández et al 2017, Perino et al 2019, Svenning 2020, Carver et al 2021.…”

“…Together, the studies of this Special Issue highlight how restoration initiatives in the Anthropocene should focus on conserving and promoting ecological complexity and emergent properties at multiple scales and nurturing the processes responsible for the long‐term maintenance of high biodiversity levels and ecological resilience (Bullock et al 2021, Mittelman et al 2021, Storch et al 2021). They emphasize the need for integrating pluralistic values of nature in restoration research and planning in order to find the required support to implement restoration at scale (Quintero‐Uribe et al 2022).…”

“…They emphasize the need for integrating pluralistic values of nature in restoration research and planning in order to find the required support to implement restoration at scale (Quintero‐Uribe et al 2022). Effective restoration planning also needs to consider transient dynamics and future trajectories under environmental changes to restore resilient systems for the future (Bullock et al 2021, Zurell et al 2021). This is inevitable given ongoing human‐induced climate change, the increasing mixing of biota due to globalization, as well as the widespread human transformation of landscapes worldwide, as highlighted by the theoretical analysis of Storch et al (2021).…”

“…Bullock et al (2021) question the dominant paradigm of ecological restoration for primarily focusing on re‐creating the community composition of ‘indigenous' reference systems and for prioritizing community composition over ecological processes. They suggest a shift towards achieving or increasing ecological complexity – defined as ‘the number of components in a system and the number of connections among them' (e.g.…”

Participatory scenarios for restoring European landscapes show a plurality of nature values

“…It has gained attention for targeting the restoration of self‐sustaining complex ecosystems through recovering lost species interactions and ecosystem functions, while, at the same time, addressing societal benefits and challenges entailed by nature restoration. It builds on ideas of process‐oriented and open‐ended restoration as a means to achieve the recovery of ecosystem functions (Torres et al 2018, Jepson 2019, Van Meerbeek et al 2019, Bullock et al 2021).…”