Emergent sustainability in open property regimes

Mark Moritz, Roy Behnke, Christine M. Beitl, Rebecca Bliege Bird, Rafael Morais Chiaravalloti, Julia K. Clark, Stefani A. Crabtree, Sean S. Downey, Ian M. Hamilton, Sui Chian Phang, Paul Scholte, and James A. Wilson. 2018. www.pnas.org/cgi/doi/10.1073/pnas.1812028115

Abstract
Current theoretical models of the commons assert that common-pool resources can only be managed sustainably with clearly defined boundaries around both communities and the resources that they use. In these theoretical models, open access inevitably leads to a tragedy of the commons. However, in many open- access systems, use of common-pool resources seems to be sustainable over the long term (i.e., current resource use does not threaten use of common-pool resources for future generations). Here, we outline the conditions that support sustainable resource use in open property regimes. We use the conceptual framework of complex adaptive systems to explain how processes within and couplings between human and natural systems can lead to the emergence of efficient, equitable, and sustainable resource use. We illustrate these dynamics in eight case studies of different social–ecological systems, including mobile pastoralism, marine and freshwater fisheries, swidden agriculture, and desert foraging. Our theoretical framework iden- tifies eight conditions that are critical for the emergence of sustainable use of common-pool resources in open property regimes. In addition, we explain how changes in boundary conditions may push open prop- erty regimes to either common property regimes or a tragedy of the commons. Our theoretical model of emergent sustainability helps us to understand the diversity and dynamics of property regimes across a wide range of social–ecological systems and explains the enigma of open access without a tragedy. We recom- mend that policy interventions in such self-organizing systems should focus on managing the conditions that are critical for the emergence and persistence of sustainability.

Abstract
Lampreys have a complex life cycle which includes a multi‐year infaunal larval stage (ammocoete). Gut content analysis has generally identified detritus (i.e., unidentifiable organic matter) as the major dietary component to ammocoetes, though algae can also be important. However, gut content preserves only a snapshot of the animal's diet and does not reflect assimilated material. In order to better characterise the nutritional sources supporting ammocoete growth, we analysed ammocoete body tissue and potential dietary sources at two streams using natural Δ14C and δ15N to estimate time‐integrated nutritional support. Bayesian isotope mixing models revealed differences in the importance of sources supporting ammocoetes between sites. Ammocoetes from a stream in a mixed land usage area (~50% agriculture, ~40% forest and ~10% developed) were primarily supported (mean: ~50%) by fresh terrestrial organic matter but were also supported by substantial contributions (mean: ~30%) by aged organic matter (AOM) and autochthonous material (algae; mean ~20%). In a predominantly forested (~90%) headwater stream, different modelling scenarios (uninformed or informed priors) suggested that algal support of ammocoete nutrition ranged from 7% to 45%. However, the model relying on informed priors developed from gut content analysis produced the low estimates, suggesting these were more reliable. When algae were a minor component of the nutrition at the forested site, ammocoetes were highly dependent on AOM (83 ± 26%; mean ± SD). Based on these findings, ammocoete growth and development are predicted to be strongly influenced by both land use and the availability of allochthonous and autochthonous materials of varying ages within streams.