Before-after-control-intervention Research Articles

Impacts of the installation of basking banks on four UK reptile species in a before–after control–intervention experiment

AbstractReptiles are often overlooked in conservation efforts. Hence, long‐term population data is often unavailable, and evidence for effective conservation actions that improve reptile habitat remains scarce for most species. Here we used a before–after control–intervention (BACI) experiment to investigate the impact of basking bank creation on four co‐occurring reptile species: European adder, barred grass snake, slow worm, and viviparous lizard. Long‐term refuge monitoring at a UK wildlife reserve allowed population assessment before and after habitat modification. Only viviparous lizards were observed at basking banks within 12 months of construction. In subsequent years, barred grass snake observations increased near basking banks and slow worms were observed for the first time, while European adder observations increased away from banks and barred grass snake observations decreased away from banks. Our small‐scale BACI study suggests basking banks attracted barred grass snakes from the surrounding area, which saw a corresponding increase in European adder sightings.

Swimmer's itch control: Timely waterfowl brood relocation significantly reduces an avian schistosome population and human cases on recreational lakes.

Swimmer's itch (SI) is a dermatitis in humans caused by cercariae of avian and mammalian schistosomes which emerge from infected snails on a daily basis. Mitigation methods for SI have long been sought with little success. Copper sulfate application to the water to kill the snail hosts is the historically employed method, but is localized, temporary, and harmful to many aquatic species. Here, we test an alternative method to control Trichobilharzia stagnicolae, a species well-known to cause SI in northern Michigan and elsewhere in North America. Summer relocation of broods of the only known vertebrate host, common merganser (Mergus merganser), greatly reduced snail infection prevalence the following year on two large, geographically separated lakes in northern Michigan. Subsequent years of host relocation achieved and maintained snail infection prevalence at ~0.05%, more than an order of magnitude lower than pre-intervention. A Before-After-Control-Intervention (BACI) study design using multiple-year snail infection data from two intervention lakes and three control lakes demonstrates that dramatic lake-wide reduction of an avian schistosome can be achieved and is not due to natural fluctuations in the parasite populations. The relevance of reducing snail infection prevalence is demonstrated by a large seven-year data set of SI incidence in swimmers at a high-use beach, which showed a substantial reduction in SI cases in two successive years after relocation began. In addition, data from another Michigan lake where vertebrate-host based intervention occurred in the 1980's are analyzed statistically and show a remarkably similar pattern of reduction in snail infection prevalence. Together, these results demonstrate a highly effective SI mitigation strategy that avoids the use of environmentally suspect chemicals and removes incentive for lethal host removal. Biologically, the results strongly suggest that T. stagnicolae is reliant on the yearly hatch of ducklings to maintain populations at high levels on a lake and that the role of migratory hosts in the spring and fall is much less significant.

Evaluating the impacts of a large-scale voluntary REDD+ project in Sierra Leone

Carbon offsets from the REDD+ (reducing emissions from deforestation and degradation) framework to protect forests are expected to see a 100-fold increase in market value by 2050. However, independent causal impact evaluations are scarce and only a few studies assess benefits to communities themselves, a core objective of REDD+. Following a pre-analysis plan, we use a before-after-control-intervention (BACI) framework to evaluate the impact of a large-scale voluntary REDD+ project in Sierra Leone—the Gola project. We use a panel of both satellite images and household surveys to provide causal evidence of the impact of the project on local deforestation rates and socioeconomic indicators over the first 5 yr of its implementation. We find that REDD+ slowed deforestation by 30% relative to control communities while not changing economic wellbeing and conservation attitudes. We find suggestive evidence that the programme increased the value of alternative income sources, by shifting labour away from forest-dependent farming activities. A cost-to-carbon calculation shows that REDD+ led to 340,000 tCO2 in avoided emissions per year, with an estimated cost of US$1.12 per averted tCO2. Our study contributes to developing an evidence base for voluntary REDD+ projects and offers a robust approach to carry out BACI assessments.

Before‐after‐control‐impact field experiment shows anti‐predator netting enhances occupancy of the threatened Hungarian meadow viper (Vipera ursinii rakosiensis)

The Hungarian meadow viper is an endangered grassland‐dwelling species, which faces high predation pressure, partially due to avian species that forage in its habitat. Predation pressure by avian predators is caused not only by abundant game species (e.g. hooded crow, Corvus cornix) but also by protected and threatened species (e.g. short‐toed eagle, Cricaetus gallicus; common buzzard, Buteo buteo; roller, Coracias garrulus) in the project area (Felső‐kiskunsági turjánvidék, Hungary). Mark–recapture data of a reintroduced viper population showed a very low, 42% yearly average apparent survival rate. To establish a strong sub‐population we applied anti‐predator netting (APN) by building a 200 × 200 × 3 m (4 ha) totally closed exclusion site with a mesh net, lateral sides boosted with a 1 m high steel field fence to exclude mammals as well as birds. To test the effect of APN we monitored viper occupancy at 50 × 50 m sampling plots in a before–after/control–intervention (BACI) design, where we randomly placed quadrats 0.25 ha (50 × 50 m) to be surveyed, n = 26 at control habitats and n = 4 below the APN enclosure. We collected data across four years (2020–2023), in each year during the spring by 10 surveys replicates in each plot resulting in 1200 surveys to record viper detection/non‐detection data. We applied a multi‐season occupancy model to estimate site occupancy changes to test the effects of the BACI design. Occupancy probabilities were increasing during the four consecutive survey years in both the control and the intervention sites, however except for the initial occupancy, the occupancy probability became significantly higher at APN sites, and the APN intervention had a significant positive effect on viper occupancy, while the distance to APN showed negative effect. Predator exclusion is an effective method to minimise predation pressure and potentially has a deterministic positive demographic outcome, however, due to the high logistical and maintenance costs, this measure can be applied at only a few sites.

Does REDD+ Complement Law Enforcement? Evaluating Impacts of an Incipient Initiative in Madre de Dios, Peru

Subnational initiatives to Reduce Emissions from Deforestation and forest Degradation and enhance carbon stocks (REDD+) have been implemented across the tropics over the last decade. Such initiatives are often embedded within pre-existing conservation policies, such as forest law enforcement, making it challenging to disentangle attributable impacts. In this article, we analyze a new REDD+ project implemented in Brazil nut concessions in the southeastern Peruvian Amazon. Public law enforcement to verify compliance with Peru's Forest Law was already ongoing and intensified locally during our study period. Thus, we combine longitudinal data from remote sensing and household surveys of 197 concessionaires in a before–after control-intervention (BACI) study design to: a) evaluate the project's impacts during the 2012–2018 period on deforestation, forest degradation, and the participants' wellbeing and b) assess how the law-enforcing field inspections may have complemented the project effects. Our results show that the REDD+ initiative had insignificant effects on deforestation and forest degradation, but confirm the curbing effects of the field inspection measures on forest loss. The non-significance of the REDD+ effects may reflect delays in cash incentive payments to enrolled concessionaires, lack of careful alignment of benefit provision with project participants, and limited enforcement of project conditionalities. Most REDD+ participants reported a reduced subjective wellbeing, which may reflect the frustrated expectations associated with project implementation. We discuss the implications of our results and outline lessons for similar tropical forest conservation initiatives.

Management of Invasive Water Hyacinth as Both a Nuisance Weed and Invertebrate Habitat

Author(s): Donley Marineau, Erin; Perryman, Matthew J.; Lawler, Sharon P.; Hartman, Rosemary K.; Pratt, Paul D. | Abstract: Invasive species have many detrimental ecological and socio-economic effects. However, invasive species can also provide novel habitat for native species. The growing rate of biological invasions world-wide presents an urgent dilemma: how can natural resource managers minimize negative effects of invasive species without depleting native taxa that have come to rely on them? Adaptive management can provide a means to address this dilemma when invasive species management plans are crafted in novel environments. We present a case study of research in support of adaptive management that considers the role of invasive water hyacinth (Eichhornia crassipes [Mart.] Solms [Pontederiaceae]) management, using herbicides, in aquatic food web functioning in the Sacramento–San Joaquin River Delta of California, USA (the “Delta”). We hypothesized that herbicide applications under current management protocols would reduce the abundance and diversity of aquatic invertebrates because they would alter both structural and biological habitat. Using a Before, After, Control, Intervention (BACI) experiment, we sampled invertebrates per gram plant biomass before and 4 weeks after glyphosate applications in treated and untreated locations. There was more plant biomass in the late-season samples because dead, dying, and living plant materials were compacted. However, there were no detectable differences between control and treated sites — or for samples before versus after the treatment date—for invertebrate abundance, species richness, or evenness. This case study demonstrates that even decaying water hyacinth serves as habitat for invertebrates that may be forage for Delta fishes. We concluded that current management practices using glyphosate do not affect invertebrate abundance during a month-long period of weed decay. These results provide valuable feedback for the “evaluate and respond” component of the adaptive management process for water hyacinth control, and demonstrate how managers globally can and should consider potential food web effects in the course of their invasive species management efforts.

Restoration of blanket peat moorland delays stormflow from hillslopes and reduces peak discharge

Over the past 15 years there has been a proliferation of projects aiming to restore the structure and function of UK upland blanket mires, primarily by revegetation of bare peat and the blocking of erosion gullies. These restoration measures have potential to alter stormflow responses and contribute to Natural Flood Management, but their impacts on storm hydrographs are poorly quantified. This paper reports a before-after-control-intervention (BACI) study from three experimental headwater micro-catchments in the South Pennines (UK) representing the first rigorous experimental assessment of the impact of blanket peat restoration on catchment runoff. We evaluate the hydrological impacts of two standard restoration interventions; revegetation of bare peat, and revegetation of bare peat with additional gully blocking. Following revegetation there was a significant decrease in depth to water table and an increase in the prevalence of hillslope overland flow production. There were no significant changes in storm runoff coefficient following either restoration treatment. Storm hydrographs following revegetation had significantly longer lag times (106% increase relative to the control), reduced peak flows (27% decrease relative to the control), and attenuated hydrograph shapes. With the addition of gully blocking the effect is almost doubled. Lag times increased by a further 94% and peak flows reduced by an additional 24% relative to the control. We argue that the primary process controlling the observed changes in storm hydrograph behaviour is retardation of overland stormflow due to increased surface roughness. The significant changes to lag times and peak flow provide evidence that the restoration of degraded headwater peatlands can contribute to Natural Flood Management and the reduction of downstream flood risk, subject to wider catchment scale effects and sub-catchment storm hydrograph synchronicity.

Measuring Subjective Flood Resilience in Suburban Dakar: A Before–After Evaluation of the “Live with Water” Project

In the last decade, sub-Saharan African countries have taken various measures to plan for and adapt to floods in order to reduce exposure and its impacts on human health, livelihoods, and infrastructure. Measuring the effects of such initiatives on social resilience is challenging as it requires to combine multiple variables and indicators that embrace thematic, spatial, and temporal dimensions inherent to the resilience thinking and concept. In this research, we apply a subjective resilience indicator framework and a before-after-control-intervention (BACI) evaluation to empirically measure the impacts of the “Live with Water” (LWW) project on suburban households in Dakar, Senegal. Our framework is based on an empirically measurable resilience index that combines anticipatory, adaptive, and absorptive capacity—considered as structural dimensions—with the concept of transformative capacity—considered as a temporal reconfiguration of the first three dimensions. Our finding let us estimate that the project increased the absorptive and the anticipatory capacities by 10.6% and 4.6%, respectively. However, adaptive capacity remained unchanged. This may be explained by the fact that the project was more successful in building drainage and physical infrastructures, rather than improving multi-level organizations and strategies to cope with existing flood events. Decoupling implementation time between physical infrastructures and longer term institutional and livelihood based support could both improve projects’ results and their evaluations.

Evaluating the Contribution of Community-based Ecotourism (CBET) to Household Income and Livelihood Changes: A Case Study of the Chambok CBET Program in Cambodia

Community-based ecotourism (CBET) has become a popular tool, especially in developing countries, for biodiversity conservation and livelihood improvement, but there is a lack of studies that use quantitative data to evaluate the effectiveness of CBET using a before-after-control-intervention (BACI), BA, or CI design. We conducted a case study of the flagship Chambok CBET program in Cambodia to quantify the contribution of CBET to household income and livelihood changes for CBET and non-CBET members. We conducted an interview survey of 173 households (77 CBET and 96 non-CBET members) that were selected systematically from every two households along roads within the same villages. There was no significant difference between the total income of member and non-member households; the median CBET income was 1.22 USD per month, which is only 1.65% of the total income. The inequality of income from CBET among the CBET members was higher than that from other income sources. The perceptions of livelihood changes differed considerably before and after the establishment of the Chambok CBET program, although this difference was not attributed to CBET but rather to general socioeconomic changes in the country. We conclude that it is challenging to employ CBET to achieve poverty reduction and livelihood improvement.

Gender lessons for climate initiatives: A comparative study of REDD+ impacts on subjective wellbeing

Although REDD+ is primarily a mechanism for reducing carbon emissions from forests, concerns regarding social benefits, wellbeing and gender are increasingly part of its mandate. This is consistent with the Paris Declaration as well as SDG 5 on gender equality and women’s empowerment. Critics have argued, however, that REDD+ design, both in policy and projects, does not take gender into account effectively, rather marginalizing women from decision making processes and exacerbating inequalities. Most of that research has been site specific or on single countries. This article uses data from a longitudinal study of subnational REDD+ initiatives in six countries to analyze their gendered impact on perceived wellbeing. Comparative research on subjective wellbeing was conducted at 62 villages participating in 16 REDD+ initiatives and 61 control villages at two periods in time, using a before-after-control-intervention (BACI) design. Focus groups with villagers (68% male) and women (100% female) permit a gendered comparison of definitions of wellbeing and outcomes of initiatives. The results highlight that while definitions of wellbeing overlapped between the two groups, almost half of the women’s focus groups thought that having their own source of income was important. Outcomes regarding wellbeing change suggest that perceived wellbeing decreased in REDD+ villages both for villagers as a whole and for women, relative to control villages, but the decrease was much worse for women – a decrease that is significantly associated with living in a REDD+ village. These declines may be due to unrealized expectations for REDD+, combined with little attention to gender in REDD+ initiatives, in spite of an important portion (46%) of specific interventions that women view positively. These interventions provide insights into potential ways forward. Overall, however, REDD+ initiatives appear to be repeating past mistakes, with insufficient attention to gender equality and safeguarding women’s rights. More effort needs to be paid to ensuring that gender is an integral part of future initiatives to combat climate change in rural communities.

Comparing methods for assessing the effectiveness of subnational REDD+ initiatives

The central role of forests in climate change mitigation, as recognized in the Paris agreement, makes it increasingly important to develop and test methods for monitoring and evaluating the carbon effectiveness of REDD+. Over the last decade, hundreds of subnational REDD+ initiatives have emerged, presenting an opportunity to pilot and compare different approaches to quantifying impacts on carbon emissions. This study (1) develops a Before-After-Control-Intervention (BACI) method to assess the effectiveness of these REDD+ initiatives; (2) compares the results at the meso (initiative) and micro (village) scales; and (3) compares BACI with the simpler Before-After (BA) results. Our study covers 23 subnational REDD+ initiatives in Brazil, Peru, Cameroon, Tanzania, Indonesia and Vietnam. As a proxy for deforestation, we use annual tree cover loss. We aggregate data into two periods (before and after the start of each initiative). Analysis using control areas (‘control-intervention’) suggests better REDD+ performance, although the effect is more pronounced at the micro than at the meso level. Yet, BACI requires more data than BA, and is subject to possible bias in the before period. Selection of proper control areas is vital, but at either scale is not straightforward. Low absolute deforestation numbers and peak years influence both our BA and BACI results. In principle, BACI is superior, with its potential to effectively control for confounding factors. We conclude that the more local the scale of performance assessment, the more relevant is the use of the BACI approach. For various reasons, we find overall minimal impact of REDD+ in reducing deforestation on the ground thus far. Incorporating results from micro and meso level monitoring into national reporting systems is important, since overall REDD+ impact depends on land use decisions on the ground.

Building the evidence base for REDD+: Study design and methods for evaluating the impacts of conservation interventions on local well-being.

Climate change mitigation in developing countries is increasingly expected to generate co-benefits that help meet sustainable development goals. This has been an expectation and a hotly contested issue in REDD+ (reducing emissions from deforestation and forest degradation) since its inception. While the core purpose of REDD+ is to reduce carbon emissions, its legitimacy and success also depend on its impacts on local well-being. To effectively safeguard against negative impacts, we need to know whether and which well-being outcomes can be attributed to REDD+. Yet, distinguishing the effects of choosing particular areas for REDD+ from the effects of the interventions themselves remains a challenge. The Global Comparative Study (GCS) on REDD+ employed a quasi-experimental before-after-control-intervention (BACI) study design to address this challenge and evaluate the impacts of 16 REDD+ pilots across the tropics. We find that the GCS approach allows identification of control groups that represent the counterfactual, thereby permitting attribution of outcomes to REDD+. The GCS experience belies many of the common critiques of the BACI design, especially concerns about collecting baseline data on control groups. Our findings encourage and validate the early planning and up-front investments required to evaluate the local impacts of global climate change mitigation efforts with confidence. The stakes are high, both for the global environment and for local populations directly affected by those efforts. The standards for evidence should be concomitantly high.

Effectiveness of Print Education at Reducing Urban Mosquito Infestation through Improved Resident-Based Management.

Improving resident-based management and knowledge of mosquitoes is often an integral component of integrated mosquito management, especially in urban landscapes with considerable mosquito habitat on privately owned lands. This study tested the effectiveness of print education materials at reducing urban mosquito exposure through improving resident knowledge of, and attitudes towards, mosquitoes and mosquito management in Washington DC, USA. There was a specific focus on the removal of water-filled containers that are utilized by the developmental stages of the two most common vector species in the region, Aedes albopictus and Culex pipiens. Households in six neighborhoods that varied in socio-economic status were administered knowledge, attitude, and practice (KAP) surveys in 2010 and 2012, and had their yards surveyed for container habitats and immature mosquitoes (larvae and pupae) in 2010, 2011, and 2012. Half the households (intervention, n = 120) received education materials in 2011 and 2012 to yield a before-after control-intervention (BACI) design. Unexpectedly, residents in intervention households were more likely to show decreased concern for mosquito-borne illnesses than residents in control households, which did not receive materials. Moreover, there was a greater probability that control households reduced containers in 2012 than intervention households, particularly when they had low numbers of baseline (2010) containers. Irrespective of control, reductions in containers were associated with decreased abundances of immature mosquitoes. Overall, our findings suggest that print education materials may have unintended negative effects on resident attitudes and household management of mosquito production. We recommend that mosquito control agencies need to carefully consider their content of print messages and the effectiveness of strategies that passively convey information with little or no engagement with control professionals.

Change detection of storm runoff and sediment yield using hydrologic models following wildfire in a coastal redwood forest, California

This study attempted to detect changes in stormflow volumes, peakflows, and sediment loads using hydrologic models within the context of an uncertainty assessment following wildfire. In 2009, after 8 years of study, the Lockheed Fire burned the treatment and control watersheds of a paired watershed study in coastal California, USA, eliminating the ability to continue a paired watershed before–after control–intervention (BACI) study design. An alternative analysis was used to detect stormflow and sediment load changes due to the wildfire by comparing measured posttreatment stormflow and sediment load with simulated predisturbance responses predicted with the hydrologic models HBV-EC and DHSVM. High natural variability of stormflow and sediment measurements compounded with uncertainty associated with the hydrologic models and climate suggest that only large changes can be detected. The fire and subsequent salvage harvest created an approximately 9%–12% reduction in forest overstory canopy and a 70%–90% consumption of understory vegetation. No discernible changes in slopes of regression lines were detected between predisturbance and postfire stormflow volumes, peakflows, or sediment loads. No changes were detected in stormflow volume, peakflow, or sediment loads comparing pre- and post-fire vegetation inputs to the hydrologic model DHSVM. The lack of detected change in streamflow to accelerate stream channel erosion combined with low to moderate fire severity adjacent to stream channels most likely were the reasons for no detected postfire change to sediment loads.

Effect of contemporary forest harvesting practices on headwater stream temperatures: Initial response of the Hinkle Creek catchment, Pacific Northwest, USA

We investigated the effect of contemporary forest harvesting practices on warm-season thermal regimes of headwater streams using a Before-After-Control-Intervention (BACI) design within a nested, paired watershed study. We applied harvesting treatments to four headwater tributaries of Hinkle Creek, designed in accordance with the Oregon Forest Practices Act. Therefore, fixed-width buffer strips containing overstory merchantable trees were not left adjacent to the four non-fish-bearing streams. The summer following harvesting, we observed a variable temperature response across the four harvested streams. Mean maximum daily stream temperatures ranged from 1.5°C cooler to 1.0°C warmer relative to pre-harvest years. We also observed significantly lower minimum and mean daily stream temperatures, and recorded particularly low temperatures in treatment streams on days that minimum stream temperatures in reference streams were high. At the watershed scale, we did not observe cumulative stream temperature effects related to harvesting 14% of the watershed area in multiple, spatially-distributed harvest units across four headwater catchments. At the watershed outlet, we observed no change to maximum, mean, or minimum daily stream temperatures. We attribute the lack of consistent temperature increases in headwater streams to shading provided by a layer of logging slash that deposited over the streams during harvesting, and to increased summer baseflows. Comparisons of canopy cover before and after harvesting indicate little change in canopy cover when logging slash is considered, indicating that logging slash affected energy balances within the streams. However, other ecosystem-level effects of logging slash in forest streams are difficult to predict. In order to devise optimum practices related to in-stream slash management, forest scientists and policymakers should continue to study and consider the potential impacts of logging slash to stream ecosystems.

Ecosystem recovery in restored headwater streams: the role of enhanced leaf retention

Summary There is controversy over how the success of ecological restoration should be measured. Traditionally, emphasis has been placed on species diversity and other community attributes, whereas the restoration of ecosystem processes has received less attention. Here, we combine replicated field experiments and a field survey to provide an ecosystem‐level measure of stream restoration success. Numerous headwater streams in Finland, and in many other parts of the world, have been channelized for timber transport, resulting in channels with simplified structure and flow. Recently, programmes have been launched to restore these streams to their pre‐channelization condition. While the efficacy of restoration in improving fish habitat has been tested, little is known about effects on other stream biota or on the retention of leaf litter, despite its importance in trophic dynamics of forested headwater streams. Using a before‐after‐control‐intervention (BACI) designed experiment with multiple reference and experimental streams, we examined restoration‐induced changes in retention efficiency by conducting leaf‐release experiments before (1993) and after (1996) restoration. Substrate heterogeneity increased, but moss cover decreased dramatically following restoration. Retention efficiency in restored streams was higher than in channelized, but lower than in natural, streams. Algae‐feeding scrapers were the only macroinvertebrate group whose density increased significantly after restoration. Aquatic mosses were a key retentive feature in both channelized and natural streams, but their importance to retention was strikingly reduced by restoration. During restoration work, mosses are detached from large areas of the stream bed, exposing bare stone surfaces for colonization by periphytic algae. A more effective restoration technique would involve the use of moss transplants, or the addition of large woody debris, to increase retentiveness and thus enhance the availability of organic material to benthic consumers. This case study on rivers illustrates how restoration projects benefit from an ecosystem perspective and from measures of ecosystem processes in assessing restoration success.