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Geology topics

Alexander S. Flecker

Publications and source records attributed to Alexander S. Flecker.

8 recordsLinked to original sources
USGS2025

Eradication efforts catalyze rapid evolution in an invasive predatory fish

pecies invasions spur costly and labor-intensive control efforts, yet even local eradication is seldom achieved. When control measures are initially effective, they may drive evolutionary adaptation that prevents full eradication, as has been documented for some chemical and biocontrol approaches. Although the intensity, directionality, and persistence of selection required to increase the frequency of resistant genotypes in complex natural ecosystems remains an open question, theory predicts that high mortality can cause life-history evolution even in the absence of a strong selective agent. Here, we use annually collected ecological and genetic data to show that rapid evolution of introduced smallmouth bass has undermined a 20-y manual suppression effort in a mid-sized lake. Despite nearly doubling annual mortality, our intensive control program produced a larger bass population dominated by young and early-maturing fish. These shifts were accompanied by large allele frequency changes in three genomic regions associated with earlier maturation and increased somatic growth. Our findings bear out the theoretical prediction that high mortality can drive evolutionary adaptation in target species. Controlling species invasions are worldwide practices that typically remove a substantial proportion of a population during each of many successive generations, hence life history adaptation may be commonplace. Such evolutionary responses could be salient in explaining the widespread failure of invasion control efforts. Genetic and phenotypic monitoring to detect cryptic adaptation and preemptive design of invader eradication programs to deliberately disrupt directional selection for resistance could improve invasion control outcomes.

New York↗
USGS2022

Biodiversity underpins fisheries resilience to exploitation in the Amazon River basin.

Inland fisheries feed greater than 150 million people globally, yet their status is rarely assessed due to their socio-ecological complexity and pervasive lack of data. Here, we leverage an unprecedented landings time series from the Amazon, Earth's largest river basin, together with theoretical food web models to examine (i) taxonomic and trait-based signatures of exploitation in inland fish landings and (ii) implications of changing biodiversity for fisheries resilience. In both landings time series and theory, we find that multi-species exploitation of diverse inland fisheries results in a hump-shaped landings evenness curve. Along this trajectory, abundant and large species are sequentially replaced with faster growing and smaller species. Further theoretical analysis indicates that harvests can be maintained for a period of time but that continued biodiversity depletion reduces the pool of compensating species and consequently diminishes fisheries resilience. Critically, higher fisheries biodiversity can delay fishery collapse. Although existing landings data provide an incomplete snapshot of long-term dynamics, our results suggest that multi-species exploitation is affecting freshwater biodiversity and eroding fisheries resilience in the Amazon. More broadly, we conclude that trends in landings evenness could characterize multi-species fisheries development and aid in assessing their sustainability.

Amazon River basin↗
USGS2021

Substitution of inland fisheries with aquaculture and chicken undermines human nutrition in the Peruvian Amazon

With declining capture fisheries production, maintaining nutrient supplies largely hinges on substituting wild fish with economically comparable farmed animals. Although such transitions are increasingly commonplace across global inland and coastal communities, their nutritional consequences are unknown. Here, using human demographic and health information, and fish nutrient composition data from the Peruvian Amazon, we show that substituting wild inland fisheries with chicken and aquaculture has the potential to exacerbate iron deficiencies and limit essential fatty acid supplies in a region already experiencing high prevalence of anaemia and malnutrition. Substituting wild fish with chicken, however, can increase zinc and protein supplies. Chicken and aquaculture production also increase greenhouse gas emissions, agricultural land use and eutrophication. Thus, policies that enable access to wild fisheries and their sustainable management while improving the quality, diversity and environmental impacts of farmed species will be instrumental in ensuring healthy and sustainable food systems.

Peruvian Amazon↗
USGS2021

Climate change may impair electricity generation and economic viability of future Amazon hydropower

Numerous hydropower facilities are under construction or planned in tropical and subtropical rivers worldwide. While dams are typically designed considering historic river discharge regimes, climate change may induce large-scale alterations in river hydrology. Here we analyze how future climate change will affect river hydrology, electricity generation, and economic viability of > 350 potential hydropower dams across the Amazon, Earth’s largest river basin and a global hotspot for future hydropower development. Midcentury projections for the RCP 4.5 and 8.5 climate change scenarios show basin-wide reductions of river discharge (means, 13 and 16%, respectively) and hydropower generation (19 and 27%). Declines are sharper for dams in Brazil, which harbors 60% of the proposed projects. Climate change will cause more frequent low-discharge interruption of hydropower generation and less frequent full-capacity operation. Consequently, the minimum electricity sale price for projects to break even more than doubles at many proposed dams, rendering much of future Amazon hydropower less competitive than increasingly lower cost renewable sources such as wind and solar. Climate-smart power systems will be fundamental to support environmentally and financially sustainable energy development in hydropower-dependent regions.

Global Environmental Change↗
USGS2019

Reducing greenhouse gas emissions of Amazon hydropower with strategic dam planning

Hundreds of dams have been proposed throughout the Amazon basin, one of the world’s largest untapped hydropower frontiers. While hydropower is a potentially clean source of renewable energy, some projects produce high greenhouse gas (GHG) emissions per unit electricity generated (carbon intensity). Here we show how carbon intensities of proposed Amazon upland dams (median = 39 kg CO 2 eq MWh −1 , 100-year horizon) are often comparable with solar and wind energy, whereas some lowland dams (median = 133 kg CO 2 eq MWh −1 ) may exceed carbon intensities of fossil-fuel power plants. Based on 158 existing and 351 proposed dams, we present a multi-objective optimization framework showing that low-carbon expansion of Amazon hydropower relies on strategic planning, which is generally linked to placing dams in higher elevations and smaller streams. Ultimately, basin-scale dam planning that considers GHG emissions along with social and ecological externalities will be decisive for sustainable energy development where new hydropower is contemplated.

Nature Communications↗
USGS2019

Ecosystem function and services of aquatic predators in the Anthropocene

Arguments for the need to conserve aquatic predator (AP) populations often focuses on the ecological and socio-economic roles they play. Here, we summarize the diverse ecosystem functions and services connected to APs, including regulating food webs, cycling nutrients, engineering habitat, transmitting diseases/parasites, mediating ecological invasions, effecting climate, supporting fisheries, generating tourism, and providing bioinspiration. In some cases, human-driven declines and increases in AP populations have altered these ecosystem functions and services. We present a Social Ecological Framework for supporting adaptive management decisions involving APs in response to social and environmental change. We also identify outstanding questions to guide future research on the ecological functions and ecosystem services of APs in a changing world

Trends in Ecology and Evolution↗
USGS2018

Efficiently optimizing for dendritic connectivity on tree-structured networks in a multi-objective framework

We provide an exact and approximation algorithm based on Dynamic Programming and an approximation algorithm based on Mixed Integer Programming for optimizing for the so-called dendritic connectivity on tree-structured networks in a multi-objective setting. Dendritic connectivity describes the degree of connectedness of a network. We consider different variants of dendritic connectivity to capture both network connectivity with respect to long and short-to-middle distances. Our work is motivated by a problem in computational sustainability concerning the evaluation of trade-offs in ecosystem services due to the proliferation of hydropower dams throughout the Amazon basin. In particular, we consider trade-offs between energy production and river connectivity. River fragmentation can dramatically affect fish migrations and other ecosystem services, such as navigation and transportation. In the context of river networks, different variants of dendritic connectivity are important to characterize the movements of different fish species and human populations. Our approaches are general and can be applied to optimizing for dendritic connectivity for a variety of multi-objective problems on tree-structured networks.

Conference Paper↗