A framework for ecological restoration cost accounting across context and scale

Restoration programs that can deliver implementation outcomes across large-scales are critical to achieving global conservation targets such as Target 2 of the Kunming-Montreal Global Biodiversity Framework. Yet, limited funding poses a strong barrier to the achievement of these ambitious goals, suggesting the adoption of emerging technologies capable of delivering cost-effective solutions to restoration at scale may be required. To date, there has been limited reporting of restoration implementation costs at scales that are meaningful for decision making, hindering the capacity for evidence-based comparisons of existing and emerging restoration methods. Here, we demonstrate the application of a detailed framework that addresses the shortcomings of previous frameworks by matching the costs of conservation actions to their outcomes across multiple scales. We estimate the financial costs of two planting methods from the perspective of a restoration practitioner comparing an established method (tubestock planting) to an emerging method (drone seeding: seed pelleting and delivery via drones), across five spatial scales (1, 10, 100, 500, and 1000 ha). Using data from a hypothetical case-study, we show that both methods exhibit economies of scale (decrease in the cost per hectare to action with increase in scale); however, the economies of scale were greater for drone seeding. Our framework allows for transparent cost accounting of project implementation to guide practitioners and policy makers when budgeting and reporting costs for future projects. Users of this framework can also explore if and how context influences the costs of restoration to maximise the delivery of cost-efficient restoration at scale.