Harnessing ecological theory to enhance ecosystem restoration.

Ecosystem restoration can increase the health and resilience of nature and humanity. As a result, the international community is championing habitat restoration as a primary solution to address the dual climate and biodiversity crises. Yet most ecosystem restoration efforts to date have underperformed, failed, or been burdened by high costs that prevent upscaling.

Dead foundation species drive ecosystem dynamics.

Foundation species facilitate communities, modulate energy flow, and define ecosystems, but their ecological roles after death are frequently overlooked. Here, we reveal the widespread importance of their dead structures as unique, interacting components of ecosystems that are vulnerable to global change. Key metabolic activity, mobility, and morphology traits of foundation species either change or persist after death with important consequences for ecosystem functions, biodiversity, and subsidy dynamics.

Long-distance facilitation of coastal ecosystem structure and resilience.

Biotic interactions that hierarchically organize ecosystems by driving ecological and evolutionary processes across spatial scales are ubiquitous in our biosphere. Biotic interactions have been extensively studied at local and global scales, but how long-distance, cross-ecosystem interactions at intermediate landscape scales influence the structure, function, and resilience of ecological systems remains poorly understood. We used remote sensing, modeling, and field data to test the hypothesis that the long-distance impact of an invasive species dramatically affects one of the largest tidal flat ecosystems in East Asia.

An invasive species erodes the performance of coastal wetland protected areas.

The world has increasingly relied on protected areas (PAs) to rescue highly valued ecosystems from human activities, but whether PAs will fare well with bioinvasions remains unknown. By analyzing three decades of seven of the largest coastal PAs in China, including World Natural Heritage and/or Wetlands of International Importance sites, we show that, although PAs are achieving success in rescuing iconic wetlands and critical shorebird habitats from once widespread reclamation, this success is counteracted by escalating plant invasions. Plant invasions were not only more extensive in PAs than non-PA controls but also undermined PA performance by, without human intervention, irreversibly replacing expansive native wetlands (primarily mudflats) and precluding successional formation of new native marshes.

Consumer regulation of the carbon cycle in coastal wetland ecosystems.

Despite escalating anthropogenic alteration of food webs, how the carbon cycle in ecosystems is regulated by food web processes remains poorly understood. We quantitatively synthesize the effects of consumers (herbivores, omnivores and carnivores) on the carbon cycle of coastal wetland ecosystems, 'blue carbon' ecosystems that store the greatest amount of carbon per unit area among all ecosystems. Our results reveal that consumers strongly affect many processes of the carbon cycle.

Sea-level rise and the emergence of a keystone grazer alter the geomorphic evolution and ecology of southeast US salt marshes.

Keystone species have large ecological effects relative to their abundance and have been identified in many ecosystems. However, global change is pervasively altering environmental conditions, potentially elevating new species to keystone roles. Here, we reveal that a historically innocuous grazer-the marsh crab -is rapidly reshaping the geomorphic evolution and ecological organization of southeastern US salt marshes now burdened by rising sea levels.

Supporting Spartina: Interdisciplinary perspective shows Spartina as a distinct solid genus.

In 2014, a DNA-based phylogenetic study confirming the paraphyly of the grass subtribe Sporobolinae proposed the creation of a large monophyletic genus Sporobolus, including (among others) species previously included in the genera Spartina, Calamovilfa, and Sporobolus. Spartina species have contributed substantially (and continue contributing) to our knowledge in multiple disciplines, including ecology, evolutionary biology, molecular biology, biogeography, experimental ecology, biological invasions, environmental management, restoration ecology, history, economics, and sociology. There is no rationale so compelling to subsume the name Spartina as a subgenus that could rival the striking, global iconic history and use of the name Spartina for over 200 yr.

A natural history model of New England salt marsh die-off.

Natural history gave birth to ecology and evolutionary biology, but today its importance is sometimes marginalized. Natural history provides context for ecological research, a concept that we illustrate using a consumer-driven vegetation die-off case study. For three decades, local predator depletion promoted the formation of high-density crab (Sesarma reticulatum) grazing and burrowing fronts, resulting in the spread of vegetation die-off through southern New England and Long Island marshes.

Facilitative and competitive interaction components among New England salt marsh plants.

Intra- and interspecific interactions can be broken down into facilitative and competitive components. The net interaction between two organisms is simply the sum of these counteracting elements. Disentangling the positive and negative components of species interactions is a critical step in advancing our understanding of how the interaction between organisms shift along physical and biotic gradients.

Multiple stressors and the potential for synergistic loss of New England salt marshes.

Climate change and other anthropogenic stressors are converging on coastal ecosystems worldwide. Understanding how these stressors interact to affect ecosystem structure and function has immediate implications for coastal planning, however few studies quantify stressor interactions. We examined past and potential future interactions between two leading stressors on New England salt marshes: sea-level rise and marsh crab (Sesarma reticulatum) grazing driven low marsh die-off.

Bottom-up and top-down human impacts interact to affect a protected coastal Chilean marsh.

Many ecosystems, even in protected areas, experience multiple anthropogenic impacts. While anthropogenic modification of bottom-up (e.g.

Direct and indirect trophic effects of predator depletion on basal trophic levels.

Human population growth and development have heavily degraded coastal ecosystems with cascading impacts across multiple trophic levels. Understanding both the direct and indirect trophic effects of human activities is important for coastal conservation. In New England, recreational overfishing has triggered a regional trophic cascade.

Positive interactions expand habitat use and the realized niches of sympatric species.

Niche theory, the oldest, most established community assembly model, predicts that in sympatry, the realized niche will contract due to negative interspecific interactions, but fails to recognize the effects of positive interactions on community assembly. The stress gradient hypothesis predicts that positive interactions expand realized niches in stressful habitats. We tested the predictions of the stress gradient hypothesis in a cobble beach model system across both physical and biological stress gradients.

Flowering and biomass allocation in U.S. Atlantic coast Spartina alterniflora.

Premise Of The Study: Salt marshes are highly productive and valuable ecosystems, providing many services on which people depend. Spartina alterniflora Loisel (Poaceae) is a foundation species that builds and maintains salt marshes. Despite this species' importance, much of its basic reproductive biology is not well understood, including flowering phenology, seed production, and the effects of flowering on growth and biomass allocation.

Indirect human impacts turn off reciprocal feedbacks and decrease ecosystem resilience.

Creek bank salt marsh die-off is a conservation problem in New England, driven by predator depletion, which releases herbivores from consumer control. Many marshes, however, have begun to recover from die-off. We examined the hypothesis that the loss of the foundation species Spartina alterniflora has decreased facilitator populations, weakening reciprocal positive plant/animal feedbacks, resilience, and slowing recovery.

Extreme stresses, niches, and positive species interactions along stress gradients.

Since proposed two decades ago, the stress-gradient hypothesis (SGH), suggesting that species interactions shift from competition to facilitation with stress, has been widely examined. Despite broad support across species and ecosystems, ecologists debate whether the SGH applies to extreme environments, arguing that species interactions switch to competition or collapse under extreme stress. We show that facilitation often expands distributions on species borders.

Experimental predator removal causes rapid salt marsh die-off.

Salt marsh habitat loss to vegetation die-offs has accelerated throughout the western Atlantic in the last four decades. Recent studies have suggested that eutrophication, pollution and/or disease may contribute to the loss of marsh habitat. In light of recent evidence that predators are important determinants of marsh health in New England, we performed a total predator exclusion experiment.

Indirect human impacts reverse centuries of carbon sequestration and salt marsh accretion.

Direct and indirect human impacts on coastal ecosystems have increased over the last several centuries, leading to unprecedented degradation of coastal habitats and loss of ecological services. Here we document a two-century temporal disparity between salt marsh accretion and subsequent loss to indirect human impacts. Field surveys, manipulative experiments and GIS analyses reveal that crab burrowing weakens the marsh peat base and facilitates further burrowing, leading to bank calving, disruption of marsh accretion, and a loss of over two centuries of sequestered carbon from the marsh edge in only three decades.

Herbivory drives the spread of salt marsh die-off.

Salt marsh die-off is a Western Atlantic conservation problem that has recently spread into Narragansett Bay, Rhode Island, USA. It has been hypothesized to be driven by: 1) eutrophication decreasing plant investment into belowground biomass causing plant collapse, 2) boat wakes eroding creek banks, 3) pollution or disease affecting plant health, 4) substrate hardness controlling herbivorous crab distributions and 5) trophic dysfunction releasing herbivorous crabs from predator control. To distinguish between these hypotheses we quantified these variables at 14 Narragansett Bay salt marshes where die-off intensity ranged from <5% to nearly 98%.

An invasive species facilitates the recovery of salt marsh ecosystems on Cape Cod.

With global increases in human impacts, invasive species have become a major threat to ecosystems worldwide. While they have been traditionally viewed as harmful, invasive species may facilitate the restoration of degraded ecosystems outside their native ranges. In New England (USA) overfishing has depleted salt marsh predators, allowing the herbivorous crab Sesarma reticulatum to denude hundreds of hectares of low marsh.

New England salt marsh recovery: opportunistic colonization of an invasive species and its non-consumptive effects.

Predator depletion on Cape Cod (USA) has released the herbivorous crab Sesarmareticulatum from predator control leading to the loss of cordgrass from salt marsh creek banks. After more than three decades of die-off, cordgrass is recovering at heavily damaged sites coincident with the invasion of green crabs (Carcinusmaenas) into intertidal Sesarma burrows. We hypothesized that Carcinus is dependent on Sesarma burrows for refuge from physical and biotic stress in the salt marsh intertidal and reduces Sesarma functional density and herbivory through consumptive and non-consumptive effects, mediated by both visual and olfactory cues.

Feedbacks underlie the resilience of salt marshes and rapid reversal of consumer-driven die-off.

Understanding ecosystem resilience to human impacts is critical for conservation and restoration. The large-scale die-off of New England salt marshes was triggered by overfishing and resulted from decades of runaway crab grazing. In 2009, however, cordgrass began to recover, decreasing die-off -40% by 2010.