Peri-urban Lakes Research Articles

Aspects of the Life Cycle of Chirostoma jordani (Pisces: Atherinopsidae) in A Periurban Lake from Mexico City: An Ecophysiological Assessment

Chirostoma jordani is an endemic species of Mexico, whose populations due to different natural and anthropogenic causes, have experienced a notable decline in recent decades, endangering their permanence in their natural habitat, including the Xochimilco canals. Therefore, this study focused on updating the status of the species in Xochimilco through an ecophysiological analysis with a bioenergetic approach, using as a model the elements (P and R) of the general energy balance equation. The measured performance indicators of the species during an annual cycle were: analysis of the structure of size (total length, TL and weight, W), body composition of the tissue: wet weight (WW), dry weight (DW), body water content (WC), nitrogen and energy content, growth rate (GR) = production (P), and metabolic rate (R) in relation to body weight in two contrasting seasons of the year (dry and rainy), as well as assimilation efficiency (P + R). The physicochemical dynamics of the habitat of the species was evaluated in all the sampling months, through eight water quality variables and was correlated with the previously indicated performance measures using discriminant analysis. The composition by sizes indicated that the spawning season and the entry of recruits into the population take place during the dry season (February - May), reaching the highest growth rates in the period March - April: 0.23 mm TL/ day, as well as the highest values in: assimilation (2,457.2 cal/g DW/day), energy expenditure in metabolism and tissue energy enrichment (CI95%: 3,493.6 – 4,762.6 cal/g DW), as opposed to the rainy season of the annual cycle: August – November, which is defined by the greatest environmental heterogeneity with extreme values of pH, total solids and nitrite concentrations that interact as constraints on the performance of the population. It is concluded that the population of C. jordani in the study area is subject to extreme environmental pressures, and the quantitative indicators used are of great value to identify and diagnose the risk status of the species and should be used to delimit future actions in its management and conservation.

Ecosystem services and green infrastructure planning of peri-urban lakes: the multifunctionality of Situ Jatijajar and Situ Pengasinan in Depok, Indonesia

This study considers multifunctionality as an all-encompassing concept that addresses the complexity and uncertainty of peri-urban areas towards sustainable landscape development by exemplifying two peri-urban lakes in Depok, which is part of the Jakarta Metropolitan Region, as case studies. This paper applies the analytical framework by Hansen and Pauleit that combines the concepts of ecosystem services and green infrastructure planning to illustrate the complex interrelation of landscape elements and their capacities to deliver multiple ecosystem services. It reveals the different spatial challenges faced by the peri-urban lakes that occurred due to the fragmented nature of landscape in peri-urban areas which has led to the development of different vulnerabilities and resilience capacities of the lakes over time. This study highlights the important roles of local actors and communities in the valuation of ecosystem services and in shaping the peri-urban pathways towards multifunctionality.

Insights into the cyanosphere: capturing the respective metabolisms of cyanobacteria and chemotrophic bacteria in natural conditions?

Specific interactions have been highlighted between cyanobacteria and chemotrophic bacteria within the cyanosphere, suggesting that nutrients recycling could be optimized by cyanobacteria/bacteria exchanges. In order to determine the respective metabolic roles of the cyanobacterial and bacterial consortia (microbiome), a day-night metatranscriptomic analysis was performed on Dolichospermum sp. (N2 -fixer) and Microcystis sp. (non N2 -fixer) natural blooms occurring successively within a French peri-urban lake. The taxonomical and functional analysis of the metatranscriptoms have highlighted specific association of bacteria within the cyanosphere, driven by the cyanobacteria identity, without strongly modifying the functional composition of the microbiomes, suggesting functional redundancy within the cyanosphere. Moreover, the functional composition of these active communities was driven by the living mode. During the two successive bloom events, it appeared that NH4 + (newly fixed and/or allochthonous) was preferentially transformed into amino acids for the both the microbiome and the cyanobacteria, while phosphate metabolism was enhanced, suggesting that due to a high cellular growth, P limitation might take place within the cyanosphere consortium.

250-year records of mercury and trace element deposition in two lakes from Cajas National Park, SW Ecuadorian Andes

Historical records of trace elements in lake sediments provide source-to-sink information about potentially toxic pollutants across space and time. We investigated two lakes located at different elevations in the Ecuadorian Andes to understand how trace element fluxes are related to (i) geology, (ii) erosion in the watersheds, and (iii) local point sources and atmospheric loads. In remote Lake Fondococha (4150 m a.s.l.), total Hg fluxes stay constant between ca. 1760 and 1950 and show an approximately 4.4-fold increase between pre-1950 and post-1950 values. The post-1950 increase in fluxes of other trace elements (V, Cr, Co, Ni, Cu, Zn, As, Cd, and Pb) is lower (2.1–3.0-fold) than for Hg. Mostly lithogenic sources and enhanced soil erosion contribute to their post-1950 increase (lithogenic contribution: > 85%, Hg: ~ 58%). Average post-1950 Hg fluxes are approximately 4.3 times higher in peri-urban Lake Llaviucu (3150 m a.s.l.) than in the remote Lake Fondococha. Post-1950 fluxes of the other trace elements showed larger differences between Lakes Fondococha and Llaviucu (5.2 < 25–29.5-fold increase; Ni < Pb–Cd). The comparison of the post-1950 average trace element fluxes that are derived from point and airborne sources revealed 5–687 (Hg–Pb) times higher values in Lake Llaviucu than in Lake Fondococha suggesting that Lake Llaviucu’s proximity to the city of Cuenca strongly influences its deposition record (industrial emissions, traffic, caged fishery). Both lakes responded with temporary drops in trace element accumulations to park regulations in the 1970s and 1990s, but show again increasing trends in recent times, most likely caused by increase in vehicular traffic and openings of copper and gold mines around Cajas National Park.

Ecological dynamics of a peri-urban lake: a multi-proxy paleolimnological study of Cultus Lake (British Columbia) over the past ~ 200 years

Peri-urban lakes offer many valued ecosystem services, but their vulnerability to climate change and anthropogenic disturbances increases with increasing human populations the effects and interactions of multiple stressors on lakes can lead to unexpected outcomes, affecting societal and ecological values, it is necessary to evaluate ecosystem trajectories and respective drivers in peri-urban lakes. Better management practices could thus be applied to preserve ecosystem services of peri-urban lakes. We conducted a multi-proxy paleolimnological study on Cultus Lake, British Columbia, a Canadian peri-urban lake experiencing cultural eutrophication, to reconstruct a comprehensive ecological trajectory of the lake over the past ~ 200 years. We also integrated historical data as well as historical archival information to identify the potential drivers of the changes. We identified ca. 1800–1900 CE as a reference period, reflected in muted variations across most paleo-indicators. Minor increases in sedimentary δ15N ca. 1880–1940 CE coincided with the onset of anthropogenic modifications to the Cultus Lake watershed. Signs of early eutrophication were evident by ca. 1940 CE, as indicated by increases in all sedimentary pigments. By ca. 1970–1990 CE, elevated concentrations of sedimentary cyanobacterial pigments and changes in diatom species assemblages highlighted the potential interactive effects of multiple stressors, including cultural eutrophication, climate warming and declines in the endangered Cultus Lake sockeye salmon population. Recent (ca. 1990–2008 CE) declines in sedimentary pigments and increases in cladoceran fluxes suggested an increase in top-down control of the lake food web. From the collection of changes observed in the past ~ 200 years in our study, it is clear that Cultus Lake and its associated ecosystem services would benefit from abatement of nutrient loadings from terrestrial and atmospheric sources. Our study emphasizes the complexity and interactivity of drivers in peri-urban lake ecosystems and the necessity of long-term perspectives to contextualize modern ecological conditions to inform lake and watershed management.

Eutrophication forcings on a peri-urban lake ecosystem: Context for integrated watershed to airshed management.

Peri-urban lakes increasingly experience intensified anthropogenic impacts as watershed uses and developments increase. Cultus Lake is an oligo-mesotrophic, peri-urban lake near Vancouver, British Columbia, Canada that experiences significant seasonal tourism, anthropogenic nutrient loadings, and associated cultural eutrophication. Left unabated, these cumulative stresses threaten the critical habitat and persistence of two endemic species at risk (Coastrange Sculpin, Cultus population; Cultus Lake sockeye salmon) and diverse lake-derived ecosystem services. We constructed water and nutrient budgets for the Cultus Lake watershed to identify and quantify major sources and loadings of nitrogen (N) and phosphorus (P). A steady-state water quality model, calibrated against current loadings and limnological data, was used to reconstruct the historic lake trophic status and explore limnological changes in response to realistic development and mitigation scenarios. Significant local P loadings to Cultus Lake arise from septic leaching (19%) and migratory gull guano deposition (22%). Watershed runoff contributes the majority of total P (53%) and N (73%) loads to Cultus Lake, with substantial local N contributions arising from the agricultural Columbia Valley (41% of total N load). However, we estimate that up to 66% of N and 70% of P in watershed runoff is ultimately sourced via deposition from the nutrient-contaminated regional airshed, with direct atmospheric deposition on the lake surface contributing an additional 17% of N and 5% of P. Thus, atmospheric deposition is the largest single source of nutrient loading to Cultus Lake, cumulatively responsible for 63% and 42% of total N and P loadings, respectively. Modeled future loading scenarios suggest Cultus Lake could become mesotrophic within the next 25 years, highlighting a heightened need for near-term abatement of P loads. Although mitigating P loads from local watershed sources will slow the rate of eutrophication, management efforts targeting reductions in atmospheric-P within the regional airshed are necessary to halt or reverse lake eutrophication, and conserve both critical habitat for imperiled species at risk and lake-derived ecosystem services.

Histological alterations of selected tissues (gill, liver, kidney and stomach) in two common fish species within two eutrophic peri-urban lakes in Zimbabwe

Pollution threatens fish health in the eutrophic lakes, Chivero and Manyame, in Zimbabwe. Histopathological tissue alterations of two commonly consumed fish: catfish, Clarias gariepinus, and; tilapia, Oreochromis niloticus, from Lakes Chivero and Manyame were assessed between 2015 and 2016. Seventy-one (71) catfish and 81 tilapia were caught using gill nets, and samples of their gills, liver, kidney and stomach tissue were collected and assessed microscopically for manifestations of disease. Pathologies observed in the gills of tilapia and catfish from both lakes included lamellar fusion, hyperplasia of primary lamellar epithelium and disintegration of secondary lamellar epithelium. Liver histopathology revealed vacuolation, presence of melanomacrophage centres and inflammatory cell infiltration in catfish and vacuolation in tilapia from both lakes. There were no significant differences (Chi-squared-test, p > 0.05) in the frequency of occurrence of some histological lesions in tissues assessed for the unrelated catfish and tilapia in the two lakes. Lamellar fusion in the gills conjoined neighbouring lamellae suggests the presence of parasites. Melanomacrophage centres observed in catfish may reflect metal pollution. Observed lesions in populations from both lakes suggest exposure to similar stressors and high tolerances and adaptation to eutrophic conditions.

Specificity of the metabolic signatures of fish from cyanobacteria rich lakes

With the increasing impact of the global warming, occurrences of cyanobacterial blooms in aquatic ecosystems are becoming a main worldwide ecological concern. Due to their capacity to produce potential toxic metabolites, interactions between the cyanobacteria, their cyanotoxins and the surrounding freshwater organisms have been investigated during the last past years. Non-targeted metabolomic analyses have the powerful capacity to study simultaneously a high number of metabolites and thus to investigate in depth the molecular signatures between various organisms encountering different environmental scenario, and potentially facing cyanobacterial blooms.In this way, the liver metabolomes of two fish species (Perca fluviatilis and Lepomis gibbosus) colonizing various peri-urban lakes of the Île-de-France region displaying high biomass of cyanobacteria, or not, were investigated. The fish metabolome hydrophilic fraction was analyzed by 1H NMR analysis coupled with Batman peak treatment for the quantification and the annotation attempt of the metabolites. The results suggest that similar metabolome profiles occur in both fish species, for individuals collected from cyanobacterial blooming lakes compared to organism from non-cyanobacterial dominant environments. Overall, such environmental metabolomic pilot study provides new research perspectives in ecology and ecotoxicology fields, and may notably provide new information concerning the cyanobacteria/fish ecotoxicological interactions.

Smart Environmental Monitoring and Assessment Technologies (SEMAT)-A New Paradigm for Low-Cost, Remote Aquatic Environmental Monitoring.

Expense and the logistical difficulties with deploying scientific monitoring equipment are the biggest limitations to undertaking large scale monitoring of aquatic environments. The Smart Environmental Monitoring and Assessment Technologies (SEMAT) project is aimed at addressing this problem by creating an open standard for low-cost, near real-time, remote aquatic environmental monitoring systems. This paper presents the latest refinement of the SEMAT system in-line with the evolution of existing technologies, inexpensive sensors and environmental monitoring expectations. We provide a systems analysis and design of the SEMAT remote monitoring units and the back-end data management system. The system’s value is augmented through a unique e-waste recycling and repurposing model which engages/educates the community in the production of the SEMAT units using social enterprise. SEMAT serves as an open standard for the community to innovate around to further the state of play with low-cost environmental monitoring. The latest SEMAT units have been trialled in a peri-urban lake setting and the results demonstrate the system’s capabilities to provide ongoing data in near real-time to validate an environmental model of the study site.

Metal accumulation in two contiguous eutrophic peri-urban lakes, Chivero and Manyame, Zimbabwe

Concentrations of aluminium, cadmium, chromium, cobalt, copper, iron, lead, nickel and zinc were determined in surface water, benthic sediments, and the gills, liver and stomach muscle tissues of Oreochromis niloticus and Clarias gariepinus in peri-urban lakes Chivero and Manyame, Zimbabwe. Five sites were sampled in each lake once per month in November 2015, February, May, August and November 2016. Pollution load index detected no metal contamination, whereas the geo-accumulation index reflected heavy to extreme sediment pollution, with Fe, Cd, Zn, Cr, Ni and Cu present in both lakes. Significant spatial temporal variations were detected for Al, Cr, Cu and Pb across sites within and between the two lakes. High Fe, Al and Cr concentrations in water and sediments in lakes Chivero and Manyame derive from geogenic background sources in addition to anthropogenic loads and intensity. Elevated concentrations of Al, Pb, Cu, Cd, Fe and Zn detected in gills, liver and stomach tissue of catfish corroborate concentrations in water and sediments, and pose the highest ecological and health risk for hydrobionts in lakes Chivero and Manyame. Contiguity of peri-urban lakes exposes them to similar threats, necessitating creative water management strategies, which ensure ecological continuity.

Vulnerability of fisherfolks and their perceptions towards climate change and its impacts on their livelihoods in a peri-urban lake system in Zimbabwe

Peri-urban fisheries- and fishing-dependent livelihoods face multiscalar threats of climate change, water pollution, transforming land initiatives and volatile markets. The objectives of this study were to assess the livelihood strategies and assets as well as the vulnerability of peri-urban fisherfolks in Lakes Chivero and Manyame, Zimbabwe. Furthermore, the study investigated the perceptions of fisherfolks towards climate change and its effects on their livelihoods. We employed a mix of qualitative and quantitative methods based on the livelihood indicator approach to assess climate risks and the associated vulnerabilities of peri-urban fisherfolks for the period November 2015–January 2017. Results indicate that the livelihood of the majority of fisherfolks (92.3% in Lake Manyame and 97.1% in Lake Chivero) is predominantly based on fishing and farming. More than 60% of the fisherfolks have attained formal education with some even attaining university education. Most (87%) peri-urban fisherfolks in the Lake Chivero and Manyame are aware of climate change and attest to its negative effects on their fishing-dependent livelihoods. Synergistic and multiplier relations between climatic and non-climatic factors such as water quality and quantity deterioration, obsolete fishing equipment and low working capital are key drivers of vulnerability. Economic diversification is the main adaptive strategy adopted by fisherfolks to reduce vulnerability. Non-significant differences in livelihood strategies, fisherfolk responses and perceptions towards climate change are attributed to the contiguity of the two lakes. Application and implementation of similar climate mitigation and adaptive strategies is a potential solution to reduce current and future vulnerability of fisherfolks in contiguous peri-urban lakes.

PERFIL SOCIOECONÔMICO DOS PESCADORES ARTESANAIS DE DOIS LAGOS PERIURBANOS DE SANTARÉM, ESTADO DO PARÁ

A atividade pesqueira tem um importante papel socioeconômico no estado do Pará, especialmente para as pequenas comunidades ribeirinhas, gerando emprego, renda e oferta de alimentos para a população. O trabalho teve como objetivo identificar o perfil socioeconômico dos pescadores e caracterizar a pesca realizada em dois lagos periurbanos de Santarém (lago Juá e Maicá), Baixo Amazonas (PA). Foram aplicados 68 formulários semiestruturados junto às lideranças, pescadores e demais atores sociais envolvidos com a pesca nas comunidades no entorno dos lagos. A maioria dos entrevistados eram do sexo masculino (69%), com idade entre 19 e 80 anos, baixos níveis de escolaridade e renda inferior a um salário mínimo. Os resultados técnico-operacionais, revelam a atividade como artesanal e de pequena escala, praticada por canoas motorizadas que variam de 2,5 a 12 m, sendo executada por pescadores de dedicação parcial ou exclusiva e com produção destinada em partes à subsistência e ao comércio, utilizando multiplicidade de apetrechos, com destaque para o uso da malhadeira e da captura de pacus, aracus, bocó (juvenil de tambaqui), jaraquis e tucunarés. Em toda extensão dos lagos ocorre a prática da pesca artesanal indicando a relevância destes mananciais como importante meio de subsistência para os pescadores locais. Como pontos negativos foram relatados a falta de fiscalização, a pesca predatória e o mau uso e degradação dos recursos naturais. Estes resultados podem subsidiar a elaboração de políticas adequadas de manejo para a melhoria da atividade pesqueira da região.

How much ecological integrity does a lake need? Managing the shores of a peri-urban lake

Physical modifications leading to a homogenization of previously diverse littoral habitats increasingly affect the ecological integrity of lake shores in urban landscapes. The European Water Framework Directive (EU WFD) requires integrative assessment of the ecological status of lake ecosystems including lake shore assessment aimed at reaching good ecological status (GES). The ecological consequences of lake shore modifications can be assessed site-specifically by ecological assessment tools based on benthic invertebrates in compliance with the EU WFD. However, it still remains unclear which percentage of the lake shore may be morphologically altered until whole-lake ecological status is affected. We studied a peri-urban lake with ∼50% of the shoreline altered by urban developments and recreational facilities and the other 50% still remaining in a near-natural, undeveloped state. We assessed the ecological status of each shore type using the Littoral Invertebrate Multimetric Index based on Composite Sampling (LIMCO). Additionally, we used data of a physical habitat survey conducted for each 100-m section within the 12-km long shoreline. We extrapolated site-specific biological assessments to the whole shore length based on pressure-response regressions using physical survey data. Our results showed an overall ‘moderate’ whole-lake ecological status and consequently the present share of near-natural shoreline is not sufficient to reach GES as required by the EU WFD. GES may be obtained by either further improving existing near-natural shorelines, or by revitalizing developed shorelines. Thus, our approach allows for the quantification of the amount of restoration necessary to derive EU WFD-compliant management objectives for lake shores subjected to human use.

Global metabolome changes induced by cyanobacterial blooms in three representative fish species

Cyanobacterial blooms induce important ecological constraints for aquatic organisms and strongly impact the functioning of aquatic ecosystems. In the past decades, the effects of the cyanobacterial secondary metabolites, so called cyanotoxins, have been extensively studied in fish. However, many of these studies have used targeted approaches on specific molecules, which are thought to react to the presence of these specific cyanobacterial compounds. Since a few years, untargeted metabolomic approaches provide a unique opportunity to evaluate the global response of hundreds of metabolites at a glance. In this way, our study provides the first utilization of metabolomic analyses in order to identify the response of fish exposed to bloom-forming cyanobacteria. Three relevant fish species of peri-urban lakes of the European temperate regions were exposed for 96h either to a microcystin (MC)-producing or to a non-MC-producing strain of Microcystis aeruginosa and metabolome changes were characterized in the liver of fish. The results suggest that a short-term exposure to those cyanobacterial biomasses induces metabolome changes without any response specificity linked to the fish species considered. Candidate metabolites are involved in energy metabolism and antioxidative response, which could potentially traduce a stress response of fish submitted to cyanobacteria. These results are in agreement with the already known information and could additionally bring new insights about the molecular interactions between cyanobacteria and fish.

Patterns and multi-scale drivers of phytoplankton species richness in temperate peri-urban lakes

Local species richness (SR) is a key characteristic affecting ecosystem functioning. Yet, the mechanisms regulating phytoplankton diversity in freshwater ecosystems are not fully understood, especially in peri-urban environments where anthropogenic pressures strongly impact the quality of aquatic ecosystems. To address this issue, we sampled the phytoplankton communities of 50 lakes in the Paris area (France) characterized by a large gradient of physico-chemical and catchment-scale characteristics. We used large phytoplankton datasets to describe phytoplankton diversity patterns and applied a machine-learning algorithm to test the degree to which species richness patterns are potentially controlled by environmental factors. Selected environmental factors were studied at two scales: the lake-scale (e.g. nutrients concentrations, water temperature, lake depth) and the catchment-scale (e.g. catchment, landscape and climate variables). Then, we used a variance partitioning approach to evaluate the interaction between lake-scale and catchment-scale variables in explaining local species richness. Finally, we analysed the residuals of predictive models to identify potential vectors of improvement of phytoplankton species richness predictive models.Lake-scale and catchment-scale drivers provided similar predictive accuracy of local species richness (R2=0.458 and 0.424, respectively). Both models suggested that seasonal temperature variations and nutrient supply strongly modulate local species richness. Integrating lake- and catchment-scale predictors in a single predictive model did not provide increased predictive accuracy; therefore suggesting that the catchment-scale model probably explains observed species richness variations through the impact of catchment-scale variables on in-lake water quality characteristics.Models based on catchment characteristics, which include simple and easy to obtain variables, provide a meaningful way of predicting phytoplankton species richness in temperate lakes. This approach may prove useful and cost-effective for the management and conservation of aquatic ecosystems.

Projecting the impact of regional land-use change and water management policies on lake water quality: an application to periurban lakes and reservoirs.

As the human population grows, the demand for living space and supplies of resources also increases, which may induce rapid change in land-use/land-cover (LULC) and associated pressures exerted on aquatic habitats. We propose a new approach to forecast the impact of regional land cover change and water management policies (i.e., targets in nutrient loads reduction) on lake and reservoir water eutrophication status using a model that requires minimal parameterisation compared with alternative methods. This approach was applied to a set of 48 periurban lakes located in the Ile de France region (IDF, France) to simulate catchment-scale management scenarios. Model outputs were subsequently compared to governmental agencies’ 2030 forecasts. Our model indicated that the efforts made to reduce pressure in the catchment of seepage lakes might be expected to be proportional to the gain that might be obtained, whereas drainage lakes will display little improvement until a critical level of pressure reduction is reached. The model also indicated that remediation measures, as currently planned by governmental agencies, might only have a marginal impact on improving the eutrophication status of lakes and reservoirs within the IDF region. Despite the commitment to appropriately managing the water resources in many countries, prospective tools to evaluate the potential impacts of global change on freshwater ecosystems integrity at medium to large spatial scales are lacking. This study proposes a new approach to investigate the impact of region-scale human-driven changes on lake and reservoir ecological status and could be implemented elsewhere with limited parameterisation. Issues are discussed that relate to model uncertainty and to its relevance as a tool applied to decision-making.

Comparative analysis of land use and lake water quality in rural and urban zones of south Chennai, India

Chennai city, the capital of Tamil Nadu state in South India, has been experiencing rapid expansion since the last two decades, resulting in major changes in land use and degradation of wetlands. Small lakes in the peri-urban areas face severe strain on their environment due to transition of rural to urban conditions, leaving at stake their aquatic health and intended uses. This paper studies the role of urbanization and land use changes in the water quality of peri-urban (Rajakilpakkam) and rural (Vengaivasal) lakes. Water samples were collected and analysed for temperature, total dissolved solids, major ions, nutrients and biological oxygen demand as per standard methods. The temperature, pH and biological oxygen demand did not differ between lakes, while total dissolved solids (p = 0.008), alkalinity (p = 0.000), total hardness (p = 0.001) and phosphate (p = 0.000) were significantly higher in Rajakilpakkam. Seasonal and spatial variations in water quality between the lakes showed the direct impact of rapid and uncontrolled growth of built-up areas in the catchment area, in enhancing waste water inflows with inorganic salts and nutrients in Rajakilpakkam lake compared with Vengaivasal lake. Urbanization of the catchment and encroachments in Rajakilpakkam lake tends to reduce the social interdependence of lake and community and promote disuse, leading to decline in water quality. The impending environmental costs caused by urbanization to these lakes will only be tackled, if the main issues of domestic and industrial discharges and encroachments are addressed properly.