Toward cross‐realm management of coastal urban ecosystems

Abstract

T he world's human population is becoming increasingly urbanized (UN 2018), posing a global threat to biodiversity and ecosystem functioning (McKinney 2006). This threat is pervasive across terrestrial, freshwater, and marine realms (here, we use the term "realm" rather than "ecosystem" to highlight the domain or sphere of influence and interconnections that terrestrial, riverine, and marine systems have on one another). The cross-realm effects of urbanization are largely driven by habitat modification to create a built environment (eg roads, buildings, stormwater infrastructure, marinas, and so forth; Trombulak and Frissell 2000;Walsh et al. 2005;Dafforn et al. 2015) and associated stressors (eg toxicants, nutrients, non-native species), which collectively threaten, degrade, and/or modify habitats (eg Airoldi et al. 2009;He et al. 2014). Such effects may propagate not only across habitat boundaries within urban realms (Lapoint et al. 2015;Bishop et al. 2017) but also across boundaries among realms (Bugnot et al. 2019) (Figure 1).Populations, communities, and ecosystems are connected via a variety of physical, biological, and chemical processes that operate at a range of spatial and temporal scales (Sheaves 2009;Lapoint et al. 2015;Bishop et al. 2017). Changes in connectivity can have substantial effects on biodiversity, productivity, energy fluxes, and food-web dynamics (Lapoint et al. 2015;Bishop et al. 2017). Urbanization can change the connectivity among realms by introducing barriers or conduits to the flow of species and resources, altering the abundance of organisms and materials that cross boundaries, and fragmenting or modifying habitats (Crook et al. 2015;Bishop et al. 2017), all of which can lead to cross-realm impacts. For example, barrages designed to protect coastal settlements from storm surges and dams that manage water flows can impede fish migrations between freshwater and marine habitats, and can starve coastal sandflats and mudflats of terrestrial sediment supplies, which are transported downstream by river systems (Figure 1; Crook et al. 2015; Bishop et al. 2017). Conversely, deforestation of catchments may increase

One hundred‐seventy years of stressors erode salmon fishery climate resilience in California’s warming landscape

“…In the case of fish, fisheries can be closed when very low abundances are forecasted (Lindley et al, 2009; Richerson et al, 2018), harvest regimes can be crafted that reduce impacts on recovering populations (e.g., Satterthwaite et al, 2018) or immature fish (e.g., size limits, terminal fisheries), and lost life histories can be “reawakened” by restoring lost habitat niches, including in salmonids via dam removal (McMillan et al, 2019; Quinn et al, 2017). As natural resource outcomes are often the product of multiple management arenas, coordinating across these arenas may synergize recovery efforts (Threlfall et al, 2021). For example, the extent to which natural‐origin juvenile salmon occupy restored habitats in the Central Valley likely depends on fisheries and flow management (Munsch et al, 2020).…”

Social–ecological connections across land, water, and sea demand a reprioritization of environmental management

“…These differing views result in a contest between reclamation (of otherwise useful land) and restoration (Williams, 1994; a real-world example of SE-P2 in Gladstone-Gallagher et al: Land to sea connections reprioritize environmental management Art. 10(1) page 7 of 18 connections (reviewed in Threlfall et al, 2021), and these examples provide insight. For example, Box 1 highlights some lessons in managing eutrophication in the Baltic Sea where collaborations across countries and agencies have begun to address the downstream effects of agriculture and urbanization on the Baltic Sea eutrophication status.…”

“…Ecological and social knowledge accumulated over decades has highlighted the role of biophysical subsidies and connectivity across a "hilltops to ocean" continuum (Polis and Hurd, 1996;Ramesh et al, 2015;Gounand et al, 2018). Despite this, management practice still tends to be isolated by ecosystem domain (Singh et al, 2021;Threlfall et al, 2021), often using different approaches and frameworks, with inequities in data and knowledge (Figure 1). Land can be privately owned, but the ocean is usually in the public domain, and this discrepancy leads to different aspirations and targets (Figure 1B).…”

A transformative mission for prioritising nature in Australian cities

“…Australia as a continent faces pressures such as more frequent droughts, bushfires and extreme heat events that are affecting the resilience of city infrastructures and city dwellers alike now and in the future (Boer et al 2020 ). Many climate change pressures are magnified for Australian cities, (Norman et al 2021 ), for example most of Australian cities are coastal and face increasing pressures from sea-level rise (Threlfall et al 2021 ). The liveability and character of Australian cities is in jeopardy if “climate-ready” interventions and policies are not promptly implemented (Ossola and Lin, 2021 ).…”