Engineering restoration for the future

Highlights

• Collaboration between ecologists and engineers is critical to large scale restoration success.

• Accounting for full life cycle ecosystem service value could justify restoration engineering R&D investment.

• New technologies for restorative earthworks and direct seeding show promise.

• Emerging restoration engineering avenues are identified and discussed.

Abstract

We posit that a better meshing of traditional engineering disciplines and ecological restoration science is central to achieving environmental repair at the scale and pace required to combat globally ever-growing, human caused, land degradation and biodiversity loss. Ecological restoration is an increasingly vibrant endeavour supported by diverse fields of research. But there is a rapidly emerging role for traditional engineering disciplines to design and deploy solutions to the challenges regularly encountered in returning biodiverse plant communities across degraded landscapes of varying characteristics. In order for large-scale restoration to be feasible, increased efficiencies throughout all stages of the restoration process are required. We argue for increased investment into the development of engineered tools and techniques guided by ecology, able to enhance our ability to cheaply, quickly, and effectively restore ecosystems. By conceptualising the overlap between ecosystem service value, traditional economic outcomes and successional land use we seek to explore how investment in new restoration technologies can lead to a net benefit for society and businesses alike. Using terrestrial mining as an example, we highlight engineering issues faced in large-scale restoration and outline how these may be overcome to maximise both economic and ecological outcomes with a particular focus on restorative earthworks and technologies for the direct return of plants.

Introduction

Recent global estimates suggest that up to two thirds of arable land is classified as degraded (Gibbs and Salmon, 2015), and that the area of undisturbed land consisting of native plant communities is in decline, predominantly as a result of clearing and unsustainable management (Hansen et al., 2013; Millennium Ecosystem Assessment, 2005). Land degradation is recognised as impacting the world's biodiversity, global climate and water supplies (Foley et al., 2005). Ecosystem repair is essential to halt, mitigate and reverse such environmental degradation for the benefit of people and nature across various scales (Hobbs and Harris, 2001) and the United Nations declaration of 2021–2030 as the Decade of Ecological Restoration is full acknowledgement of the urgent need to vastly increase restoration capabilities (UNEP, 2019).

Whilst consideration of the environmental and moral arguments for restoration should be adequate to enact action, the reality of most major land use operations (e.g. resource extraction, large-scale cropping systems, rangeland grazing, and forestry) is that they exist to service the immediate needs of the global human population and to make financial profit. Regulatory and social impetus for ecological restoration is increasing (Bullock et al., 2011; UNEP, 2019), but with a commercial entity needing to justify expenses to its stakeholders, and government expenditures to its citizens, engagement in comprehensive restoration exercises is rare. For instance, mining companies in Australia rarely set-aside sufficient, or any, rehabilitation funds to facilitate the future re-instatement of suitable levels of pre-disturbed vegetation and ecosystem function (to standards agreed with regulators) during their operations and many sites are abandoned - there is now up to 50,000 abandoned mines across Australia alone (Lamb et al., 2015).

Influencing, balancing and controlling the complex abiotic and biotic interactions that govern ecological processes to restore an ecosystem is difficult and costly, particularly at large scale and in many cases the investment in developing effective restoration techniques is low (Bourne et al., 2017; Tamura et al., 2017). However, the economic costs for restoration can be justified by recognising the value of biological processes and services that ecosystems provide (e.g. clean water, timber, carbon sequestration) (Bullock et al., 2011). That is, ecosystem services provide economic value – ecosystem service value (e.s.v.) (Costanza et al., 1997), and if large areas remain barren and devoid of functioning ecosystems, society, potentially at great cost, loses these critical services and fails to maximise the value that land provides. Growing social and political movements, such as the charity funded $56 billion valuation of the Great Barrier Reef (Deloitte, 2017) and the United Nations endorsed Bonn Challenge (IUCN, 2011), are increasingly recognising e.s.v., driving a push for large-scale, scientifically-informed restoration.

Leaving areas degraded affects subsequent development. For example the potential for agricultural, social and economically sustainable development after a major land use may be diminished (Miao and Marrs, 2000). Therefore, land usages should not be considered as individual isolated practices as the ability for a land use to provide value to society is directly linked to the state in which the preceding use left the land.

We acknowledge there is a spectrum of objectives regarding repair of degraded land (e.g. those captured by activities consistent with reclamation, rehabilitation, or restoration, as defined by The Society for Ecological Restoration International Science and Policy Working Group, 2004). Nevertheless, these activities often sit at the interface between former and future land uses and play an important role in optimising the value society can gain from this common resource when other economic activities are absent. Whilst the manipulation of biological and edaphic mechanisms and processes for ecosystem restoration continue to be extensively researched (Cleland et al., 2013; Hulvey and Aigner, 2014), research into the application of this manipulation in practice, and at large scale, is required if restoration is to be successful and as cost effective as possible (Hobbs and Norton, 1996). Only in a small number of scenarios has focussed research led to the development of techniques able to demonstrably restore degraded ecosystems to those approaching pre-disturbance conditions and that could be considered biodiverse, functional, resilient, and cohesive with the surrounding landscape; principles that are central to restoration (Society for Ecological Restoration International Science and Policy Working Group, 2004). Strip mine restoration in south west Western Australia is a prominent example (Koch and Hobbs, 2007; Rokich, 2016); however the reliance on the use of freshly stripped topsoil containing seeds to re-introduce soil and plant diversity and function limits the translation of such approaches to most other land-uses or ecosystems (Cooke and Johnson, 2002).

The need to reinstate complex biological systems using cost-effective techniques makes a multi-disciplinary partnership critical for large-scale restoration (Bradshaw, 1997). We argue that the fusion of engineering and biological sciences is key to success. Engineers, with a knowledge-base which focusses on abiotic systems, can assist in bringing scalable biotic science into practice – particularly if the economic arguments for doing so can be demonstrated. It would seem that if similar commitment to investments in the technologies to efficiently remove value from ecosystems were applied to those to restore ecosystems, better restoration outcomes would be achieved. Here we propose a conceptual framework for financial investment into engineered restoration techniques and technologies; in the context of a full land use cycle, and beyond. In particular, we focus on the mining industry as a case study to explore where major engineering advancements should and are being made to aid large scale restoration.

It should be noted that in many cases post-mined land use focusses on reclaiming the land for economic development or other uses beyond, or outside of ecological restoration seeking only to return ecosystems to pre-disturbance states. In these cases, land use succession and the economic impact of the post-mining land use is clear and favourable (Quinkenstein et al., 2012). However, if humanity is to achieve global restoration targets (UNEP, 2019) and mitigate climate change, biodiversity loss, soil erosion and other such challenges, effective ecological restoration will be required for many of these landscapes. Mining is arguably the most extreme case of human-induced disturbance to an ecosystem as it can drastically change the physical topography of a landscape, completely remove ecosystems via land clearing, and affect the water cycle via ground water extraction and pollution (Lamb et al., 2015).