Globally, conservation efforts need to be more targeted and more effective. Spatially explicit estimates of vegetation integrity are an essential tool to inform ecosystem conservation and restoration planning at a landscape scale. Yet ecological integrity is an opaque concept that is difficult to assess and enhance (Brown and Williams 2016; Rohwer and Marris 2021). To disentangle integrity, we demonstrate how tangible attributes of vegetation cover and richness can be assessed relative to their transparently defined, contemporary reference states (McNellie et al. 2020). Moreover, we deliver models that provide continuous gridded surfaces at fine scales (100 m) commensurate with the key ecological processes that shape landscape patterns. These models are focussed and data-driven, as opposed to inferential models that rely on disturbance-driven patterns (such as land use or human footprint) which aim to assess and enhance integrity based on notions of pristine, intact or pre-intensification ecosystems. However, our results show that land use was substantially more influential than other environmental or disturbance variables, suggesting that land use might be an appropriate proxy in some cases. Given our assessment of integrity can be sourced from existing data, and assessed against measurable and falsifiable benchmarks, we believe our approach could be applicable to terrestrial landscapes at a global scale.
Previous landscape-scaled assessments of integrity have used national conservation reserves (e.g., Harwood et al. 2016) or distance from human populations or infrastructure (e.g., Allan et al. 2019; Watson et al. 2018) as proxies to identify reference states from which to assess condition. However, protected areas are not always minimally disturbed and are often not representative of a majority of ecosystems (Joppa and Pfaff 2009). We found that approximately 85% of vegetation that meets or exceeds the cover benchmarks is outside the current protected area network. In contrast, 85% of the vegetation that meets or exceeds the richness benchmark is contained within the protected area network.
When using a contemporary reference frame, the intrinsic value of data-based models are useful measures of integrity, quality or condition. Here, we show that some areas with the greatest potential biodiversity value are not included in the protected area network (Archibald et al. 2020; Clements et al. 2019; De Vos and Cumming 2019). Targeting these areas may yield disproportionate benefits for conservation strategies because unprotected areas potentially face some of the greatest threats (Myers et al. 2000).
Inspection of the predicted patterns shows that, across the landscape, there is a larger area that meets or exceeds benchmark values for cover (approximately 112 000 ha) than for richness (approximately 10 000 ha). In addition, we identified areas where condition exceeds benchmark values outside the existing protected area network. Protected area status appears to be a limited indicator of vegetation integrity, especially when structural and compositional attributes are considered simultaneously. This may indicate that the composition of functional groups is more degraded and that efforts to restore landscapes will need to target species composition.
Here we have highlighted that when we use complex, multi-attribute information based on species’ observations, it is difficult for all attributes to meet their benchmark simultaneously. This paints a picture of poor or incomplete integrity when assessing the contemporary landscape. This may contrast with common perceptions of integrity, especially in protected areas. However, people, including experts in vegetation assessment, use different cues to perceive integrity. When assessing vegetation communities experts may tend to be biased towards dominant woody species (Dorrough et al. 2021), rather than overall structure or composition (such as foliage cover and native species richness among functional groups).
One of the benefits of the models presented here is that individual attributes have not been combined into an index of structural or compositional integrity. When used as standalone attributes, each can be used to inform different aspects of landscape conservation. An additional benefit is that log response ratios can be summed. As a result, different functional groups can be summed to assess the integrity of combined attributes, such as non-woody (grasses, forbs, ferns and ‘others’) or woody (trees and shrubs) components of the landscape. Furthermore, the data are on a continuous scale and can be interrogated to find patterns in vegetation integrity across the landscape for operational and practical land management and conservation, such as active restoration. Modelled surfaces can identify where in the landscape most functional groups meet benchmark levels and, therefore, can inform targeted restoration. For example, our results indicate those areas where both shrub and tree functional groups meet or exceed benchmark levels, yet active restoration may be necessary to improve the structure and composition of forbs and grasses.
Given systematic conservation planning is an inherently spatial undertaking (Pressey et al. 2000), planning can be improved when the integrity of different functional groups is considered. The maps generated here incorporate the relationship of observed states relative to contemporary reference states, which is likely to improve systematic conservation planning by identifying locations that simultaneously protect species from multiple functional groups. These maps show different degrees of change in integrity across the landscape and focus on a multi-species approach with an emphasis on structural and compositional characteristics of vegetation. These structural and compositional attributes can also serve as reliable input variables for species habitat modelling. For example, habitat models may require tailored functional groups relevant to species-specific ecological niches (Lawton et al. 2021; Robles and Ciudad 2012; van Schalkwyk et al. 2021).
Areas that could potentially be used to augment and extend the conservation network will inevitably be located on private lands. Refocusing the Global Biodiversity Framework post-2020 could concentrate new conservation efforts on creating protected areas that are tailored to meet future biodiversity targets. We have shown that some functional groups have large contiguous areas that facilitate well-connected landscapes within functional groups.