Dredging fundamentally reshapes the ecological significance of 3D terrain features for fish in estuarine seascapes

Context Landscape modification alters the condition of ecosystems and the structure of terrain, with widespread impacts on biodiversity and ecosystem functioning. Seafloor dredging impacts a diversity of flora and fauna in many coastal landscapes, and these processes also transform three-dimensional terrain features. The potential ecological significance of these terrain changes in urban seascapes has, however, not been investigated. Objectives We examined the effects of terrain variation on fish assemblages in 29 estuaries in eastern Australia, and tested whether dredging changes how fish associate with terrain features. Methods We surveyed fish assemblages with baited remote underwater video stations and quantified terrain variation with nine complementary metrics (e.g. depth, aspect, curvature, slope, roughness), extracted from bathymetry maps created with multi-beam sonar. Results Fish diversity and abundance were strongly linked to seafloor terrain in both natural and dredged estuaries, and were highest in shallow waters and near features with high curvature. Dredging, however, significantly altered the terrain of dredged estuaries and transformed the significance of terrain features for fish assemblages. Abundance and diversity switched from being correlated with lower roughness and steeper slopes in natural estuaries to being linked to features with higher roughness and gentler slopes in dredged estuaries. Conclusions Contrasting fish-terrain relationships highlight previously unrecognised ecological impacts of dredging, but indicate that plasticity in terrain use might be characteristic of assemblages in urban landscapes. Incorporating terrain features into spatial conservation planning might help to improve management outcomes, but we suggest that different approaches would be needed in natural and modified landscapes.

Habitat mediates coevolved but not novel species interactions

Ongoing recovery of native predators has the potential to alter species interactions, with community and ecosystem wide implications. We estimated the co-occurrence of three species of conservation and management interest from a multi-species citizen science camera trap survey. We demonstrate fundamental differences in novel and coevolved predator–prey interactions that are mediated by habitat. Specifically, we demonstrate that anthropogenic habitat modification had no influence on the expansion of the recovering native pine marten in Ireland, nor does it affect the predator's suppressive influence on an invasive prey species, the grey squirrel. By contrast, the direction of the interaction between the pine marten and a native prey species, the red squirrel, is dependent on habitat. Pine martens had a positive influence on red squirrel occurrence at a landscape scale, especially in native broadleaf woodlands. However, in areas dominated by non-native conifer plantations, the pine marten reduced red squirrel occurrence. These findings suggest that following the recovery of a native predator, the benefits of competitive release are spatially structured and habitat-specific. The potential for past and future landscape modification to alter established interactions between predators and prey has global implications in the context of the ongoing recovery of predator populations in human-modified landscapes.

Spatial Analysis for Landscape Changes

Landscape is the backcloth over which environmental and anthropic events occur, and recent increasing trends of natural and anthropic processes, such as urbanization, land-use changes, and extreme climate events, have a strong impact on landscape modification [...]

Sex-Biased Habitat Use by Phyllostomid Bats on Riparian Corridors in a Human Dominated Tropical Landscape

Some animal species exhibit sex-specific patterns as an adaptation to their habitats, however, adaptability to a human-dominated landscape is commonly explored without considering intraspecific sexual differences. Differences between males and females lead to a sexual segregation in habitat use. In southern Mexico, we explored sex-specific responses to landscape modification of six common species of phyllostomid bats: Artibeus jamaicensis, A. lituratus, Sturnira lilium, Carollia perspicillata, Glossophaga soricina, and Platyrrhinus helleri using riparian corridors within continuous forest and cattle pastures. Furthermore, we explored sex related responses to vegetation attributes (i.e., tree height and basal area) and seasonality (i.e., wet and dry seasons). Overall, capture rates were significantly skewed toward females and riparian corridors in pastures. Females of G. soricina exhibited a strong positive relationship with greater tree height and basal area. Seasonality was important for A. lituratus and S. lilium females, only. The results indicate a sexual driven response of bats to habitat modification. The high energetic demands of females associated to reproduction could lead to foraging into riparian corridors in pastures. The presence of large trees along riparian corridors in pastures may help maintaining a diverse and dynamic bat community in modified tropical landscapes.

A food web approach reveals the vulnerability of biocontrol services by birds and bats to landscape modification at regional scale

Pest control services provided by naturally occurring species (the so-called biocontrol services) are widely recognized to provide key incentives for biodiversity conservation. This is particularly relevant for vertebrate-mediated biocontrol services as many vertebrate species are of conservation concern, with most of their decline associated to landscape modification for agricultural purposes. Yet, we still lack rigorous approaches evaluating landscape-level correlates of biocontrol potential by vertebrates over broad spatial extents to better inform land-use and management decisions. We performed a spatially-explicit interaction-based assessment of potential biocontrol services in Portugal, using 1853 pairwise trophic interactions between 78 flying vertebrate species (birds and bats) and 53 insect pests associated to two widespread and economically valuable crops in the Euro-Mediterranean region, olive groves (Olea europaea subsp. europaea) and vineyards (Vitis vinifera subsp. vinifera). The study area was framed using 1004 square cells, each 10 × 10 km in size. Potential biocontrol services were determined at all those 10 × 10 km grid-cells in which each crop was present as the proportion of the realized out of all potential pairwise interactions between vertebrates and pests. Landscape correlates of biocontrol potential were also explored. Our work suggests that both birds and bats can effectively provide biocontrol services in olive groves and vineyards as they prey many insect pest species associated to both crops. Moreover, it demonstrates that these potential services are impacted by landscape-scale features and that this impact is consistent when evaluated over broad spatial extents. Thus, biocontrol potential by vertebrates significantly increases with increasing amount of natural area, while decreases with increasing area devoted to target crops, particularly olive groves. Overall, our study highlights the suitability of our interaction-based approach to perform spatially-explicit assessments of potential biocontrol services by vertebrates at local spatial scales and suggest its utility for integrating biodiversity and ecosystem services in conservation planning over broad spatial extents.

Direct and indirect effects of roads on space use by jaguars in Brazil

Roads pose an imminent threat to wildlife directly through mortality and changes in individual behavior, and also indirectly through modification of the amount and configuration of wildlife habitat. However, few studies have addressed how these mechanisms interact to determine species response to roads. We used structural equation modeling to assess direct and indirect effects (via landscape modification) of roads on space use by jaguars in Brazil, using radio-tracking data available from the literature. We fit path models that directly link jaguars’ space use to roads and to land cover, and indirectly link jaguars’ space use to roads through the same land cover categories. Our findings show that space use by jaguars was not directly affected by roads, but indirect effects occurred through reductions in natural areas on which jaguars depend, and through urban sprawl. Males´ space use, however, was not negatively influenced by urban areas. Since jaguars seem to ignore roads, mitigation should be directed to road fencing and promoting safe crossings. We argue that planners and managers need to much more seriously take into account the deforestation and the unbridled urban expansion from roads to ensure jaguar conservation in Brazil.

Defining dual-axis landscape gradients of human influence for studying ecological processes

Ecological processes are strongly shaped by human landscape modification, and understanding the reciprocal relationship between ecosystems and modified landscapes is critical for informed conservation. Single axis measures of spatial heterogeneity proliferate in the contemporary gradient ecology literature, though they are unlikely to capture the complexity of ecological responses. Here, we develop a standardized approach for defining multi-dimensional gradients of human influence in heterogeneous landscapes and demonstrate this approach to analyze landscape characteristics of ten ecologically distinct US cities. Using occupancy data of a common human-adaptive songbird collected in each of the cities, we then use our dual-axis gradients to evaluate the utility of our approach. Spatial analysis of landscapes surrounding ten US cities revealed two important axes of variation that are intuitively consistent with the characteristics of multi-use landscapes, but are often confounded in single axis gradients. These were, a hard-to-soft gradient, representing transition from developed areas to non-structural soft areas; and brown-to-green, differentiating between two dominant types of soft landscapes: agriculture (brown) and natural areas (green). Analysis of American robin occurrence data demonstrated that occupancy responds to both hard-to-soft (decreasing with development intensity) and brown-to-green gradient (increasing with more natural area). Overall, our results reveal striking consistency in the dominant sources of variation across ten geographically distinct cities and suggests that our approach advances how we relate variation in ecological responses to human influence. Our case study demonstrates this: robins show a remarkably consistent response to a gradient differentiating agricultural and natural areas, but city-specific responses to the more traditional gradient of development intensity, which would be overlooked with a single gradient approach. Managing ecological communities in human dominated landscapes is extremely challenging due to a lack of standardized approaches and a general understanding of how socio-ecological systems function, and our approach offers promising solutions.

Assessment of Human Modification of Landscapes: Human Perceptions vs. Analytical Indices

We assessed how close human perceptions of landscape modification matched a multivariate index based on remotely sensed data of the same locations. Using a Human Footprint (HF) map of the continental U.S. (scaled 0-100), we created three series of aerial images, each with ten images distributed evenly across the 10 deciles of HF score. Using a web-based survey, 290 members of the global public ranked the images in one series based on their perception of the degree of human modification. Respondents also reported age, sex, and country. The degree of correspondence between rankings by respondents and by HF score was high, an average of 1.29 units of difference out of a maximum possible of 5.0. Differences among respondents were not explained by age, sex, or general geographic location. These results suggest that human perception of relative landscape modification conforms closely with the relative ranking made by a multivariate, analytical index.

The Anthropocene

Soon, the Anthropocene will be formally submitted as a chronostratigraphic unit of the Geological Time Scale. This means, in effect, that Homo sapiens will be recognized as a dominant geological force on the planet. But how are anthropologists engaging with this concept in ways that inform larger debates? And what vital concerns or challenges are being raised by anthropologists and scholars in related disciplines as the Anthropocene becomes an increasingly familiar framework for understanding humanity and its place on Earth? One of the underlying motives for the recognition of the Anthropocene is to call attention to humanity’s pervasive impacts on the planet, which are understood as largely damaging for humans and other organisms that live on the Earth. However, the Anthropocene’s root causes still remain hotly disputed. Some see the Anthropocene as a broader extension of humanity’s long-established tendency of landscape modification or niche construction while others assert that the capitalist system is the underlying cause of the Anthropocene’s emergence. Extending from these debates, anthropologists and other social scientists have looked into the ways that the Anthropocene intersects with histories of race and racism, colonialism and neocolonialism, extraction and extinction, and what anthropological methods—from archaeological excavation to multispecies ethnography—can tell us about the differing dimensions of this confounding time. In a more philosophical vein, the Anthropocene has prompted academic researchers to question basic disciplinary distinctions, heuristics, and taken-for-granted assumptions. For anthropologists specifically, it has prompted a re-evaluation of human-centered analytics and inherited notions about what constitutes “the human.” Without a doubt, this literature and the scholarly debates that animate it will only grow and evolve with time, but here a focus is placed on the origins and politics of the Anthropocene, with specific focus on its relationship to historical and contemporary inequalities. This bibliography also considers what the Anthropocene means for socio-cultural theory, anthropological methods, and movements toward decolonization and collective liberation in a deeply compromised world.