Tina Parkhurst

1. Carbon plantings are a vital contribution to mitigate climate change. While plantings are primarily done for carbon sequestration, there is potential for biodiversity co-benefits, particularly when plantings mirror the local reference ecosystem and comprise a mix of native species with a variety of functional traits. With the continued rise of carbon plantings globally, the potential for biodiversity co-benefits also increases.

2. Biodiversity co-benefits are relevant to emerging biodiversity markets, new restoration laws in Europe and global aspirational goals for a Nature Positive future. Uncertainty among proponents is prevalent because measuring biodiversity co-benefits is more complex than measuring carbon sequestration. While there are standardised methodologies for measuring carbon sequestration, there is little guidance for practitioners on how to identify and quantify biodiversity co-benefits.

3. Here, we present practical guidelines, informed by a real-world case study, for identifying potential biodiversity values and their subsequent quantification in biodiverse carbon plantings. Key elements include desktop analyses to identify the landscape and ecosystem context, including threatened ecosystems and species, and threatening processes. We provide guidance on monitoring approaches for key abiotic and biotic ecosystem characteristics at baseline and reference states.

4. Practical implications. These guidelines allow integration of measured biodiversity outcomes with existing frameworks such as Natural Capital Accounting standards and Nature-related Financial Disclosure frameworks. These are increasingly implemented by businesses worldwide to assess and report their nature-related impacts, dependencies and risks. Together, these frameworks are necessary to ensure that corporations' financial investments in a Nature Positive future result in a net benefit for native ecosystems and people.

Global mining activities are critical for socio-economic prosperity yet threaten the biological diversity that underpins it. The risks of mining impacts on biodiversity are currently unknown because these impacts are underreported. The global ecosystem accounting standard offers a solution to monitor, mitigate, and report mining impacts comprehensively. This is urgently needed to achieve global targets to reverse biodiversity loss.

Demand for ecological restoration of Earth's degraded ecosystems has increased significantly since the adoption of The Kunming-Montreal Global Biodiversity Framework in December 2022, with target 2 aiming to ensure that at least 30% of degraded ecosystems are under effective restoration by 2030. More recently, in December 2023, the Australian Parliament introduced the Nature Repair Act, which establishes a framework for the world's first legislated, national, voluntary biodiversity market. How can the effectiveness of these ambitious targets be measured? Natural Capital Accounting (NCA) provides a framework to measure changes in ecosystem condition that is applicable across ecosystems and potentially catalogue effects of restoration interventions to drive investment, improvement to practice, and ultimately, to better protect the Earth's ecosystems. However, the framework has not been tested in this context. In this progressive approach, we populated the leading global NCA framework with ecological data to quantify changes in ecosystem condition after restoration. In principle, NCA is fit for purpose, however, methodological refinements and ecological expertise are needed to unlock its full potential. These tweaks will facilitate adoption and standardisation of reporting as efforts ramp up to meet ambitious global restoration targets.

The conversion of woodland ecosystems to agricultural landscapes has led to unprecedented losses of biodiversity and ecosystem functioning globally. Unsustainable agricultural practices have contributed to the degradation of soil's physical and biogeochemical properties. Ecological restoration of unproductive agricultural land is imperative for reversing land degradation and ameliorating the degrading effects of agriculture on biodiversity and ecosystem functions. However, it is unclear to what extent common restoration activities, such as tree planting, can facilitate the recovery of ecosystem condition and in particular, improve soil physical, biogeochemical and biotic components. Here, we investigated how the cessation of cropping, followed by tree planting, affected soil carbon concentrations and key biophysical soil functions. Data were collected across 10 sites a decade after the replanting of woody species on old fields in semi-arid Western Australia. We applied a chronosequence approach and measured soil functions in fallow cropland (restoration starting point), 10-year-old planted old fields and intact woodland reference sites (restoration target point). We stratified sampling between open areas and patches under trees in planted old fields and reference woodlands to account for inherent biophysical differences. Soils under planted trees recovered to some extent, having reduced soil compaction and higher soil penetration depth in comparison with the fallow cropland. However, soils under trees in planted old fields did not reach woodland reference conditions for these properties. Moreover, recovery was not evident for other soil physical, biogeochemical and biotic components such as soil organic carbon, soil moisture, leaf litter and woody debris decomposition rates. Limited recovery of soil functions may be at least partly explained by time lags associated with slow growth rates of planted trees in dry ecosystems. Our study shows that the legacy of cropping can persist over long timeframes in semi-arid regions, with modest signs of woodland recovery beginning to emerge 10 years after tree planting.

The breakdown of plant material fuels soil functioning and biodiversity. Currently, process understanding of global decomposition patterns and the drivers of such patterns are hampered by the lack of coherent large-scale datasets. We buried 36,000 individual litterbags (tea bags) worldwide and found an overall negative correlation between initial mass-loss rates and stabilization factors of plant-derived carbon, using the Tea Bag Index (TBI). The stabilization factor quantifies the degree to which easy-to-degrade components accumulate during early-stage decomposition (e.g. by environmental limitations). However, agriculture and an interaction between moisture and temperature led to a decoupling between initial mass-loss rates and stabilization, notably in colder locations. Using TBI improved mass-loss estimates of natural litter compared to models that ignored stabilization. Ignoring the transformation of dead plant material to more recalcitrant substances during early-stage decomposition, and the environmental control of this transformation, could overestimate carbon losses during early decomposition in carbon cycle models.

Nature-based solutions (NbS) have emerged at the science, policy and practitioner interface to address environmental challenges facing society. NbS involve people working with nature to protect, restore or manage ecosystems. Yet NbS vary to the extent they support biological diversity which has implications for ecological resilience.

We reviewed how ecological resilience has been conceptualised in the NbS literature. The literature included reference to both resilience to specific disturbances and general resilience to future environmental change.

We found reporting of resilience mechanisms was limited except for afforestation efforts where there is increasing recognition of the role of species diversity in contributing to resilience. Reporting was limited for resilience mechanisms that operate within species and populations (e.g. genetic diversity) and at the landscape scale (e.g. connectivity). Resistance was overlooked despite the prevalence of NbS intended to address climate change. From the broader ecological literature, we distilled resilience mechanisms that have been identified for native and experimental ecosystems and suggested interventions for the emergence of resilience mechanisms in NbS.

Synthesis. Interventions to conserve biodiversity such as retaining and restoring ecosystems, are critical given that biodiversity, within and across scales of biological organisation, underpins several ecological resilience mechanisms in NbS.

Restoration of old fields in agricultural landscapes has become increasingly important for conservation of species and their habitats owing to habitat destruction and rapid environmental change. Studies examining the outcomes of old field restoration predominantly focus on plant, and sometimes, vertebrate communities. Fewer studies have systematically investigated the effects of restoration efforts on soil properties or ground‐dwelling invertebrates and there is limited synthesis of these data.

We conducted a global meta‐analysis of published studies to assess the effects of old field restoration on soil properties and soil invertebrate abundance and richness. We anticipated increased vegetation cover would improve soil properties towards reference condition and in turn, this would promote invertebrate abundance and richness. Studies were included if field sites had a history of cropping or livestock grazing.

We identified 42 studies (1994–2019) from 16 countries that met our criteria. More studies assessed passive restoration methods than active planting, and native species were more commonly planted than exotic species.

Results showed that restoration improved soil conditions with respect to total nitrogen, magnesium, soil carbon, bulk density and porosity when compared to controls; however, conditions similar to those in reference ecosystems were generally not achieved, even 50+ years after restoration had been initiated. Moderator analyses showed few significant tends, however, bulk density improved with age, and in passively restored versus reference ecosystems. Outcomes for soil carbon and bulk density were most predominant in the top soil when compared to the degraded ecosystem. We detected no consistent trends for the effect of restoration on soil invertebrate richness and abundance compared to the control or reference ecosystems.

Synthesis and applications. Our global meta‐analysis found strong evidence that old field restoration in agricultural landscapes had positive effects on soil condition but did not lead to full recovery when compared to a reference ecosystem. We detected few and idiosyncratic effects for invertebrates. Further research is needed to understand effects of restoration on soil invertebrate functional groups and to develop management interventions that accelerate the restoration of soil condition.

Many old fields are undergoing ecological restoration aiming to return lost biodiversity and ecosystem functions. However, there is scant evidence that this outcome is achieved. Here we investigate the effects of tree planting following cessation of cropping on ant communities. Ants are a dominant faunal group, functionally important for ecosystem recovery and widely used as indicators of ecosystem restoration. Using a space-for-time approach, we surveyed eight fallow croplands, 10-year-old planted old fields, and reference woodlands in semi-arid south-western Australia. We tested the extent ant communities in planted old fields diverged from those of fallow cropland and converged with those of reference woodlands, distinguishing areas under tree canopies and open patches to account for a direct tree effect. We analyzed ant community data at species, genus, and functional-group levels. Ant species composition in planted old fields substantially converged from fallow croplands toward reference woodlands. Abundance and richness of genera in the tree-associated functional group Subordinate Camponotini was higher under trees than in open areas in planted old fields and reference woodlands. Unlike in reference woodlands, abundance and richness of Hot Climate Specialists was not higher in open areas than under trees in planted old fields, indicating that planted trees did not yet strongly impact the microclimate beneath them. Although old field restoration had positive effects on ant assemblages, full convergence to reference woodlands had not been achieved after 10 years. This was particularly evident for functional groups. Research on older plantings is needed to test if and when full convergence occurs.

Understanding constraints to ecological restoration on former agricultural land has become increasingly important due to agricultural land degradation in the developed world, and growing evidence for enduring agricultural legacies that limit native species recovery. In particular, the removal of native plant biomass and subsequent disturbance of soil properties through farming activities can alter soil ecosystem processes. Planting of native plant species is a common approach to restoring native vegetation on agricultural land and is assumed to benefit soil ecosystem processes, but the degree to which altered soil chemical processes recover is poorly documented. We investigated recovery of soil chemical properties after restoration in semiarid Western Australia, hypothesizing that elevated nutrient concentrations would gradually decline post planting, but available phosphorus (P) concentrations would remain higher than reference conditions. We used a space-for-time substitution approach, comparing 10 planted old field plots with matched fallow cropland and reference woodlands. Sampling on planted old fields and reference woodland plots was stratified into open patches and under tree canopy to account for consistent differences between these areas. The most prominent legacy of cropping was significantly and substantially higher concentrations of soil available P in fallow croplands and restored old fields compared with reference woodlands. Soil mineral nitrogen (N) concentrations were elevated in fallow croplands compared to open patches in reference woodlands (ammonium and nitrate) and under the tree canopy (ammonium). However, in restored old fields, mineral N concentrations were similar to woodland sites, providing evidence for amelioration over time. No significant differences in nutrient concentrations under tree canopies compared with open patches had developed in the planted old fields, despite a distinction between open patches and he under ttree canopy in reference woodlands for total N. We conclude that soil P legacies in old fields may inhibit the recolonization of native species that are sensitive to, or uncompetitive at, elevated P concentrations. To achieve full recovery, further research is required to test restoration practices aimed at reducing soil P concentrations to facilitate native plant establishment and persistence.

Ecological restoration of former agricultural land can improve soil conditions, recover native vegetation, and provide fauna habitat. However, restoration benefits are often associated with time lags, as many attributes, such as leaf litter and coarse woody debris, need time to accumulate. Here, we experimentally tested whether adding mulch and logs to restoration sites in semi-arid Western Australia can accelerate restoration benefits. All sites had been cropped and then planted with native trees and shrubs (i.e., Eucalyptus, Melaleuca, and Acacia spp.) 10 years prior to our experiment, to re-establish the original temperate eucalypt woodland vegetation community. We used a Multi-site Before-After-Control-Impact (MBACI) design to test the effects on 30 abiotic and biotic response variables over a period of 2 years. Of the 30 response variables, a significant effect was found for just four variables: volumetric water content, decomposition, native herbaceous species cover and species richness of disturbance specialist ants. Mulch addition had a positive effect on soil moisture when compared to controls but suppressed growth of native (but not exotic) herbaceous plants. On plots with log additions, decomposition rates decreased, and species richness of disturbance specialist ants increased. However, we found no effect on total species richness and abundance of other ant species groups. The benefit of mulch to soil moisture was offset by its disbenefit to native herbs in our study. Given time, logs may also provide habitat for ant species that prefer concealed habitats. Indeed, benefits to other soil biophysical properties, vegetation, and ant fauna may require longer time frames to be detected. Further research is needed to determine whether the type, quantity, and context of mulch and log additions may improve their utility for old field restoration and whether effects on native herbs are correlated with idiosyncratic climatic conditions.