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Though cities occupy only a small percentage of Earth's terrestrial surface, humans concentrated in urban areas impact ecosystems at local, regional and global scales. I examined the direct and indirect ecological outcomes of human activities on both managed landscapes and protected native ecosystems in and around cities. First, I used highly managed residential yards, which compose nearly half of the heterogeneous urban land area, as a model system to examine the ecological effects of people's management choices and the social drivers of those decisions. I found that a complex set of individual and institutional social characteristics drives people's decisions, which in turn affect ecological structure and function across scales from yards to cities. This work demonstrates the link between individuals' decision-making and ecosystem service provisioning in highly managed urban ecosystems.
Second, I examined the distribution of urban-generated air pollutants and their complex ecological outcomes in protected native ecosystems. Atmospheric carbon dioxide (CO2), reactive nitrogen (N), and ozone (O3) are elevated near human activities and act as both resources and stressors to primary producers, but little is known about their co-occurring distribution or combined impacts on ecosystems. I investigated the urban "ecological airshed," including the spatial and temporal extent of N deposition, as well as CO2 and O3 concentrations in native preserves in Phoenix, Arizona and the outlying Sonoran Desert. I found elevated concentrations of ecologically relevant pollutants co-occur in both urban and remote native lands at levels that are likely to affect ecosystem structure and function. Finally, I tested the combined effects of CO2, N, and O3 on the dominant native and non-native herbaceous desert species in a multi-factor dose-response greenhouse experiment. Under current and predicted future air quality conditions, the non-native species (Schismus arabicus) had net positive growth despite physiological stress under high O3 concentrations. In contrast, the native species (Pectocarya recurvata) was more sensitive to O3 and, unlike the non-native species, did not benefit from the protective role of CO2. These results highlight the vulnerability of native ecosystems to current and future air pollution over the long term. Together, my research provides empirical evidence for future policies addressing multiple stressors in urban managed and native landscapes.
feedback control models of social-ecological systems (SESs), to inform policy and the
design of institutions guiding resilient resource use. Cote and Nightingale (2012) note that
the main assumptions of resilience research downplay culture and social power. Addressing
the epistemic gap between positivism and interpretation (Rosenberg 2016), this dissertation
argues that power and culture indeed are of primary interest in SES research.
Human use of symbols is seen as an evolved semiotic capacity. First, representation is
argued to arise as matter achieves semiotic closure (Pattee 1969; Rocha 2001) at the onset
of natural selection. Guided by models by Kauffman (1993), the evolution of a symbolic
code in genes is examined, and thereon the origin of representations other than genetic
in evolutionary transitions (Maynard Smith and Szathmáry 1995; Beach 2003). Human
symbolic interaction is proposed as one that can support its own evolutionary dynamics.
The model offered for wider dynamics in society are “flywheels,” mutually reinforcing
networks of relations. They arise as interactions in a domain of social activity intensify, e.g.
due to interplay of infrastructures, mediating built, social, and ecological affordances (An-
deries et al. 2016). Flywheels manifest as entities facilitated by the simplified interactions
(e.g. organizations) and as cycles maintaining the infrastructures (e.g. supply chains). They
manifest internal specialization as well as distributed intention, and so can favor certain
groups’ interests, and reinforce cultural blind spots to social exclusion (Mills 2007).
The perspective is applied to research of resilience in SESs, considering flywheels a
semiotic extension of feedback control. Closer attention to representations of potentially
excluded groups is justified on epistemic in addition to ethical grounds, as patterns in cul-
tural text and social relations reflect the functioning of wider social processes. Participatory
methods are suggested to aid in building capacity for institutional learning.