Anthony J. Mills
Robbert Duker
Richard G. Lechmere-Oertel3
Ruan van Mazijk
Alastair J. Potts- 1Department of Soil Science, Faculty of AgriSciences, Stellenbosch University, Stellenbosch, South Africa
- 2C4 EcoSolutions (Pty) Ltd., Cape Town, South Africa
- 3Grasslands Node, South African Environmental Observation Network (SAEON), Pietermaritzburg, South Africa
- 4Department of Biological Sciences, Faculty of Science, University of Cape Town, Cape Town, South Africa
- 5Botany Department, Nelson Mandela University, Gqeberha, South Africa
Restoring the hundreds of millions of hectares of degraded ecosystems worldwide will require new approaches to raise the required funds and new systems to implement at the required scales. Two decades of large-scale restoration in the subtropical thicket biome in the Eastern Cape, South Africa, have generated valuable information for developing such approaches and systems. The successful upscaling of restoration in this biome can be attributed to four main actions. First, from the outset in 2003, peer-reviewed science was foundational to the entire restoration initiative. Second, also from the outset, there was a commitment to large-scale, long-term ecological research by the public sector (the then Department of Water Affairs and Forestry in South Africa), which resulted in what is to our knowledge the world’s largest ecosystem restoration experiment, comprising 330 quarter-hectare plots distributed over ∼75,000 km2. Third, retrospective scientific description of previous restoration work — done by farmers in the 1960s and 1970s — provided valuable information on restoration’s multiple benefits, without having to wait for the large-scale restoration experiment to yield results. Lastly, diverse and short-term scoping studies were undertaken to address questions that emerged during the large-scale implementation of restoration. These studies were vital for rapid adaptive management and planning new scientific experiments, filling a gap between long-term ecological research and retrospective science.
1 Introduction
The UN Decade on Ecosystem Restoration calls for investments of a trillion dollars into the restoration of hundreds of millions of hectares of degraded land across the globe by 2030 (UNEP/FAO, 2020). Two decades of restoration efforts in the subtropical thicket biome in the Eastern Cape, South Africa (Mills et al., 2015) have provided some of the most valuable information available internationally to assess the investment and implementation models for such large-scale ecosystem restoration. In 2003, restoration efforts in the thicket biome were catalysed by public-sector finance with the express purpose of raising private-sector funding to take restoration from a plot scale to a biome scale. Currently, there are at least eight private-sector companies, of which we are aware, that have formed to implement thicket restoration at the scale of tens to hundreds of thousands of hectares, leading to the creation of many hundreds of jobs, and the planting of many tens of millions of cuttings of the indigenous succulent tree ‘spekboom’ (Portulacaria afra L. Jacq., Didiereaceae) (Figure 1). In short, the vision for large-scale restoration funded by the private sector developed in 2003 (Mills et al., 2007) has materialised. Here, we provide a perspective on the four main actions — that could be replicated in other ecosystems worldwide — that led to this success. We end with an overview of how we think subtropical thicket restoration efforts could be optimised and further honed over the next ten years of this multi-decadal ecosystem restoration journey.
Figure 1 Ongoing subtropical thicket ecosystem restoration and research in the Eastern Cape, South Africa. (A, B) Fence-line contrasts showing intact versus degraded thicket. (C) A nursery in the Sundays River Valley in which spekboom (Portulacaria afra) cuttings are propagated en masse in seedling trays. (D) A cutting (with a well-formed ‘root carrot’) that is ready to be planted into the field. (E) A field team planting rooted cuttings into a degraded thicket landscape. (F) A recently planted rooted cutting. (G) A thicket-wide plot that had a high survivorship of planted cuttings.
2 Actions of success to date
The first main action of success was ensuring that peer-reviewed science was foundational to the restoration programme. This required a commitment from the main stakeholders (the government department providing funding1, research institutions, and consulting scientists) to publish peer-reviewed scientific papers that would provide a credible knowledge base upon which the entire restoration programme would be built. The rationale was that private sector funders would most likely only finance large-scale projects with budgets of tens or hundreds of millions of dollars if the technical approaches and investment benefits were well documented in peer-reviewed literature. This rationale appears to have been supported in that the public founding documentation of the various implementation companies and the Verra project documentation refer extensively to the published literature, especially papers such as Mills et al. (2005); Mills and Cowling (2006); Mills and Cowling (2010) and van der Vyver et al. (2013).
The second action was committing at the outset to large-scale, long-term ecological research rather than plot-scale, short-term experiments. This commitment, maintained for two decades2, led to the establishment of what is, to our knowledge, the largest ecosystem restoration experiment in the world — 330 quarter-hectare fenced plots, distributed over the ∼75,000 km2 extent of degraded parts of the xeric succulent thicket biome (Mills et al., 2015), with 12 different restoration treatments in each plot. The success of these ‘thicket-wide plots’ (Figure 1) has also played a major role in convincing investors that large-scale restoration in the thicket biome is feasible.
The third action was identifying and studying several sites of restoration work implemented by farmers in previous decades. The retrospective scientific description of this uncoordinated restoration (e.g., Mills and Cowling, 2006; van der Vyver et al., 2013) provided sufficient insight and supporting data to interest investors and other scientists without having to wait a decade or more for the results from the thicket-wide plots. This action enabled momentum to be built within the investment community both in the private and public sectors (Mills et al., 2015) early on in the restoration journey, which was later accelerated as the results of the thicket-wide plots were published.
The fourth action ensuring success was undertaking diverse scientific scoping studies to fill specific, emerging knowledge gaps that became apparent during restoration implementation. We found that such studies (Table 1) were vital for maintaining the momentum of investment into restoration, generating the information needed for rapid adaptive management practices during project implementation, and for planning new, long-term scientific experiments.
Table 1 Scoping studies conducted in parallel with large-scale restoration of degraded subtropical thicket in the Eastern Cape, South Africa, over the period 2020–2023.
3 Inevitable knowledge gaps
Large-scale restoration will, we suggest, always have the challenge of managing knowledge gaps, no matter how rigorous the long-term ecological research and retrospective science taking place in parallel. This is because many ecological factors influence the restoration of a natural ecosystem — many of which vary on monthly, daily or even hourly bases3, and most of which will remain unmeasured, no matter how large the research budget. The consequence of so many unmeasured factors is that it is difficult to pinpoint which factors determine the success or failure of restoration in a particular long-term experimental plot, and whether success or failure in landscapes adjacent to the plot will be reproducible4.
Although the problem of unmeasured factors and unpredictable events adversely affecting the restoration outcome5 can never be fully overcome, we found that implementing diverse scoping studies (Table 1) and undertaking hourly monitoring of cuttings using camera traps provided valuable information for steering the large-scale implementation of planting tens of millions of cuttings over thousands of hectares. Scoping studies, for example, showed that pre-rooting cuttings before planting them resulted in vastly improved survivorship in both wet and dry periods. And camera traps showed which herbivores were causing the most damage to plants through uprooting and/or eating leaves, stems and bark (Table 1).
Budgetary constraints usually require prioritising certain scoping studies and monitoring procedures over others. Such decision-making is important, but our view is that the in-field brainstorming of ecologists to formulate new hypotheses and to design monitoring protocols for testing them is of even greater importance. We found that new ideas and hypotheses on how to improve the restoration process were easier to generate in the field than off-site. Without the range of competing hypotheses that were generated during weeks of observing restoration plots in a variety of landscapes, the scoping studies and monitoring we undertook would have had considerably less value6.
4 Breeding further success
Looking ahead to the next ten years of subtropical thicket restoration, as the scale of restoration increases into the hundreds of thousands of hectares, we argue that all four actions described above need to remain front and centre, but with some modifications. For the first action, we encourage funders to hold scientists accountable and ensure that data is published in peer-reviewed literature rather than languishing in unpublished reports. A large proportion of the data collected over the past two decades in subtropical thicket, funded from South African tax revenue, has not been published and is unavailable to the public. The publishing of these data and their interpretation should not rely on the intentionality of individual scientists but rather should be required by funders, with major penalties for non-compliance.
For the second action, we would advocate fundraising to implement as many long-term, large-scale experiments as possible, but with the caveat that they are monitored frequently and adjusted early on based on the findings of concurrent scoping studies. In the case of the thicket-wide plots, major investment into maintenance of the plots and examination of the effects of 15 years of restoration in terms of biodiversity, carbon capture and hydrology is now required. This investment requires intensive coordination and management by either a new coordinating institution formed for this purpose or an existing institution7.
For the third action, we suggest that project developers and funders actively seek additional sites for retrospective study. This is in contrast to a more ad hoc approach8 in which such sites are only studied if there happens to be a curious scientist involved who wants to embark on this type of work. Again, funders should hold contracted scientists accountable for publishing the data collected.
For the fourth action, we suggest that funders ensure that there is a substantial investment into applied research comprising small scoping studies that take place in parallel to the implementation of the large-scale restoration. Our experience is that there is no substitute for in-field discussions between multi-disciplinary scientists and restoration practitioners for generating worthwhile hypotheses, thought experiments, and new management approaches. We also found that scientific creativity in the field benefited greatly from certain rules of engagement: actively seeking new hypotheses to counter existing hypotheses with regards to the ecological processes at play and how restoration should be conducted; using a wide variety of thought experiments to debate the strength of the various countering hypotheses; and then using the outcome of the debates to set up scoping studies to test competing hypotheses.
Topics which we anticipate will lead to new scoping studies relate to inter alia: the facilitative role that the thicket ecosystem engineer ‘spekboom’ (P. afra) plays in promoting natural regeneration of indigenous thicket plants (Sigwela et al., 2009; van der Vyver et al., 2013); quantifying the return of bird and insect species in the thicket-wide plot experiments using eco-acoustics technology (Grant and Samways, 2016; Stowell and Sueur, 2020; Maeder et al., 2022); the considerable increase in herbivore carrying capacity once P. afra has established, and the establishment of sustainable herbivory levels to prevent re-degradation; the potential to greatly expand the range available to black rhinoceros (Diceros bicornis) by planting P. afra; the potential for nurturing cuttings in a nursery environment (using, for example, shade, mycorrhizal inoculants, fertilizer and water) that ultimately do not thrive in the field; and how to manage herbivores, whether domestic or indigenous, to enhance rather than degrade the ecological function of restored thicket.
Lastly, we note that funders and investors should be prepared for some, or even many, of these scoping studies not to go as planned. Some may fail, or yield no results of consequence, while others may yield completely unexpected results. This is the nature of ecosystem restoration: success follows a pathway of failures and surprises. Preparing for failures and welcoming surprises should consequently be fully embraced by all stakeholders embarking on a new restoration journey. Although success breeds success in large-scale restoration, failure and surprise perhaps breed even more.
Data availability statement
The original contributions presented in the study are included in the article/supplementary material. Further inquiries can be directed to the corresponding author.
Author contributions
AJM: Conceptualization, Writing – original draft, Writing – review & editing. RD: Writing – review & editing. RGL-O: Writing – review & editing. RvM: Writing – review & editing. AJP: Writing – review & editing.
Funding
The author(s) declare financial support was received for the research, authorship, and/or publication of this article. The APC for this article was covered by a grant to AJM (National Research Foundation grant number 150823).
Conflict of interest
Authors RD and RvM were employed by company C4 EcoSolutions, supervised by AJM during the course of this research.
The remaining authors declare that this research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Publisher’s note
All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.
Footnotes
- ^ At the time, the Department of Water Affairs and Forestry in South Africa.
- ^ The Subtropical Thicket Restoration Programme (STRP) was established in 2004 by the then Department of Water Affairs and Forestry (South Africa). It was formed to catalyse public and private sector funding into restoration of the thicket biome. More than 10,000 hectares of degraded thicket have been planted with spekboom cuttings through this programme to date. Unfortunately, the momentum of this government-funded programme has subsided in recent years.
- ^ e.g., soil water content; soil temperature; soil oxygen status; soil microbial activity; abundance of soil meso- and macro-fauna; soil nutrient availability; herbivory pressure from insects, reptiles and mammals; health of parent plants from which cuttings are taken.
- ^ In 2021, we planted several hundred thousand cuttings near a thicket-wide plot with high survivorship (see Figure 1G). Most of these cuttings died. We formed the view that during some months of 2021 the soils were too wet for the planted cuttings, causing rotting and termite damage, and that in other months, conditions were too dry and windy, causing desiccation and extreme herbivory pressure. Presumably, the year in which that plot was planted was neither too wet nor too dry, but data on soil water content, soil microbial activity, termite activity and herbivore pressure was not collected; it is consequently not feasible to examine this hypothesis.
- ^ Referred to as non-demonic intrusions by Hurlbert (1984).
- ^ For example, the root dynamics of planted cuttings had not been examined over the first decade of the restoration work in thicket. We found in our fieldwork that fungi and termites often damaged roots in wet soils shortly after planting unrooted cuttings, and that many old (>5 years) plants that had survived but not grown substantially often had small root masses. Understanding the dynamics of successful rooting became a major theme in our scoping studies.
- ^ e.g., the South African National Biodiversity Institute (SANBI).
- ^ Which was the case in the STRP.
References
Galuszynski N. C., Forbes R. E., Rishworth G. M., Potts A. J. (2023). Restoring South African subtropical succulent thicket using Portulacaria afra: exploring the rooting window hypothesis. PeerJ. 11, e15538. doi: 10.7717/peerj.15538
Grant P. B. C., Samways M. J. (2016). Use of ecoacoustics to determine biodiversity patterns across ecological gradients. Conserv. Biol. 30, 1320–1329. doi: 10.1111/cobi.12748
Hurlbert S. H. (1984). Pseudoreplication and the design of ecological field experiments. Ecol. Monogr. 54, 187–211. doi: 10.2307/1942661
Maeder M., Guo X., Neff F., Schneider Mathis D., Gossner M. M. (2022). Temporal and spatial dynamics in soil acoustics and their relation to soil animal diversity. PloS One 17, e0263618. doi: 10.1371/journal.pone.0263618
Mills A. J., Cowling R. M. (2006). Rate of carbon sequestration at two thicket restoration sites in the Eastern Cape, South Africa. Restor. Ecol. 14, 38–49. doi: 10.1111/j.1526-100X.2006.00103.x
Mills A. J., Cowling R. M. (2010). Below-ground carbon stocks in intact and transformed subtropical thicket landscapes in semi-arid South Africa. J. Arid Environments 74, 93–100. doi: 10.1016/j
Mills A. J., Cowling R. M., Fey M. V., Kerley G. I. H., Donaldson J. S., Lechmere-Oertel R. G., et al. (2005). Effects of goat pastoralism on ecosystem carbon storage in semiarid thicket, Eastern Cape, South Africa. Austral Ecol. 30, 797–804. doi: 10.1111/j.1442-9993.2005.01523.x
Mills A. J., Turpie J. K., Cowling R. M., Marais C., Kerley G. I. H., Lechmere-Oertel R. G., et al. (2007). “Assessing costs, benefits, and feasibility of restoring natural capital in subtropical thicket in South Africa,” in Restoring Natural Capital, Science, Business, and Practice (Washington DC: Island Press), 179–187.
Mills A. J., van der Vyver M., Gordon I. J., Patwardhan A., Marais C., Blignaut J., et al. (2015). Prescribing innovation within a large-scale restoration programme in degraded subtropical thicket in South Africa. Forests 6, 4328–4348. doi: 10.3390/f6114328
Powell M. J. (2009). Restoration of degraded subtropical thickets in the Baviaanskloof Megareserve, South Africa: The role of carbon stocks and Portulacaria afra survivorship (Makhanda, South Africa: MSc thesis. Rhodes University).
Sigwela A. M., Kerley G. I. H., Mills A. J., Cowling R. M. (2009). The impact of browsing-induced degradation on the reproduction of subtropical thicket canopy shrubs and trees. South Afr. J. Bot. 75, 262–267. doi: 10.1016/j.sajb.2008.12.001
Stowell D., Sueur J. (2020). Ecoacoustics: acoustic sensing for biodiversity monitoring at scale. Remote Sens. Ecol. Conserv. 6, 217–219. doi: 10.1002/rse2.174
UNEP/FAO (2020). The United Nations Decade on Ecosystem Restoration - Strategy. Available at: https://wedocs.unep.org/bitstream/handle/20.500.11822/31813/ERDStrat.pdf.
van der Vyver M. L., Cowling R. M., Mills A. J., Difford M. (2013). Spontaneous return of biodiversity in restored subtropical thicket: Portulacaria afra as an ecosystem engineer. Restor. Ecol. 21, 736–744. doi: 10.1111/rec.12000
van der Vyver M. L., Mills A. J., Cowling R. M. (2021). A biome-wide experiment to assess the effects of propagule size and treatment on the survival of Portulacaria afra (spekboom) truncheons planted to restore degraded subtropical thicket of South Africa. PloS One 16, e0250256. doi: 10.1371/journal.pone.02502561
Keywords: arid ecosystems, ecosystem restoration, land degradation, large-scale research, subtropical thicket
Citation: Mills AJ, Duker R, Lechmere-Oertel RG, van Mazijk R and Potts AJ (2023) Science is the fuel required for lifting ecosystem restoration into the orbit of hundreds of millions of hectares. Front. Conserv. Sci. 4:1283262. doi: 10.3389/fcosc.2023.1283262
Received: 25 August 2023; Accepted: 25 September 2023;
Published: 13 November 2023.
Edited by:
Peter Taylor, University of the Free State, South AfricaReviewed by:
Halina Teresa Kobryn, Murdoch University, AustraliaCopyright © 2023 Mills, Duker, Lechmere-Oertel, van Mazijk and Potts. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Anthony J. Mills, mills@sun.ac.za