Predicting the spread of alligator weed (Alternanthera philoxeroides) in Wular lake, India: A mathematical approach (original) (raw)
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Conserving Biological Diversity, 2016
AbstrAct Assam, a north eastern state of India is famous for its rich biodiversity and the region has been a priority for leading conservation agencies of the world. There are about 3513 freshwater wetlands in the state, which accommodate highly diverse life forms, from freshwater fishes to numerous macrophytes. With the time this rich and highly diverse wetland area has been disturbed and modified by different factors. Biological invasion by different invasive aquatic species is one of these major factors. Of all the invasive species, Alternanthera philoxeroides (Mart.) Griseb is one of the main aquatic weeds, which is currently threatening the wetlands of the state. The weed grows and spread very fast which can cover water ways and adversely affect the flow of
Alien invasive species cause significant impacts on ecosystems and economies, but the impacts on human well-being and livelihoods are less well known. Negative impacts can be particularly severe when caused by floating aquatic plants, which can reduce access to freshwater for extraction and navigation, reduce the harvest of fish and other resources, and change water cycling and chemistry. This paper reviews and discusses some of these impacts globally and then concentrates on the case study of Wular Lake, India. Wular is the largest freshwater lake in Jammu and Kashmir state and is highly important for local livelihoods through the provision of a range of services, including fish and edible aquatic plants, and water to local communities. The supply of these services has decreased due to a long history of environmental degradation , and recent invasions by the floating plants Azolla cristata and Alternanthera philoxerodies (alligator weed) have further impacted human well-being. Here, we review the published literature about these invasions, present information from interviews with locals living near Wular Lake, and review the global literature about invasive floating plant species to assess the present and predict the future impacts of these species. We find that the implications of these invasions for livelihoods reliant on lake resources and services provide good justification for management efforts. We discuss some options and challenges to such a management program.
Forecasting the Vulnerability of Lakes to Aquatic Plant Invasions
Invasive Plant Science and Management, 2014
Prevention is an integral component of many management strategies for aquatic invasive species, yet this represents a formidable task when the landscapes to be managed include multiple invasive species, thousands of waterbodies, and limited resources to implement action. Species distributional modeling can facilitate prevention efforts by identifying locations that are most vulnerable to future invasion based on the likelihood of introduction and environmental suitability for establishment. We used a classification tree approach to predict the vulnerability of lakes in Washington State (United States) to three noxious invasive plants: Eurasian watermilfoil (Myriophyllum spicatum), Brazilian egeria (Egeria densa), and curlyleaf pondweed (Potamogeton crispus). Overall, the distribution models predicted that approximately one-fifth (54 out of 319 study lakes) of lakes were at risk of being invaded by at least one aquatic invasive plant, and many of these predicted vulnerable lakes currently support high native plant diversity and endemism. Highly vulnerable lakes are concentrated in western Washington in areas with the highest human population densities, and in eastern Washington along the Columbia Basin Irrigation Project and the Okanogan River Basin that boast hundreds of lakes subject to recreational use. Overall, invasion potential for the three species was highly predictable as a function of lake attributes describing human accessibility (e.g., public boat launch, urban land use) and physical–chemical conditions (e.g., lake area, elevation, productivity, total phosphorous). By identifying highly vulnerable lake ecosystems, our study offers a strategy for prioritizing on the-ground management action and informing the most efficient allocation of resources to minimize future plant invasions in vast freshwater networks.
Border control for potential aquatic weeds. Stage 1. Weed risk model
2000
Science for Conservation is a scientific monograph series presenting research funded by New Zealand Department of Conservation (DOC). Manuscripts are internally and externally peer-reviewed; resulting publications are considered part of the formal international scientific literature. Individual copies are printed, and are also available from the departmental website in pdf form. Titles are listed in our catalogue on the website, refer www.doc.govt.nz under Publications, then Science & technical.
EC AGRICULTURE, 2019
The study was conducted from July 2014 to December 2017 in Lake Tana. Sampling sites chosen from Fogera, Libokemkem, Dembia, Bahirdarzuria and Takusa Woredas and purposive sampling sites were selected from each Woreda based on invasive weed infested areas. Plant sample was collected from infested areas using quadrant and different parameters were recorded using sensitive balance and tape meter. Dissolved oxygen (DO), pH, specific conductance (K 25), total dissolved solids (TDS), salinity (sal) and temperature (T) were measured in situ using YSI 556 multi-probe system. Measurements of ammonia (NH 3-N), phosphate (PO 4-P), nitrate (NO 3-N) and total hardness were carried out using a portable water analysis kit (Wagtech International, Palintest transmittance display photometer 5000). Water samples were collected from each sampling station up to a depth of 1m using a bucket of known volume. Zooplankton and phytoplankton samples were collected by 80 µm and 50 µm mesh net filtering device. Identification and enumeration of invasive weeds and planktons was made using standard procedures. As a result Water hyacinth, Azola, Potamogeton foliosus and water lettuce were investigated. In the case of water hyacinth hundred four plants/m 2 and 8.22 ± 0.45 kg fresh weight/ m 2 which equals to 82.16 tons/ha fresh weight could be harvested during the dry season of a year. But, 583 plants/m 2 (27.0 ± 0.61 kg fresh weight/m 2) which equals 270 tons/ha fresh weight could be harvested during the wet season of a year. The present assessment also noted that no major management strategy had been employed in the infested water body areas, despite many efforts had been applied by the community and the government. Water hyacinth (Eichhornia crassipes) is widely recognized as the world's worst aquatic weed. Originally exported from its native Amazonian basin because of its attractive flowers, the species rapidly established and spread throughout tropical, subtropical and warm temperate regions of the world [1]. It was indicated that this weed forms a dense impenetrable mats across water surface, limiting access by man, animals and machinery. Moreover, navigation and fishing are obstructed, and hydropower, irrigation as well as drainage systems become blocked. The weed was first introduced into Africa through Egypt sometimes between 1879 and 1882 (Friend, 1989). It has been recognized as the most damaging aquatic weed in Ethiopia since its first presence in 1965 [2,3]. It has been recognized its presence in lake Tana in 2011 [4]. Even though several efforts has been made by different parties, its expansion increased year after year. Therefore, there is a need to study some of its biology, impact on water quality, biota and current management options.
2017
The Midmar Dam within the uMngeni Catchment, KwaZulu-Natal is important for water provisioning and recreational use. In 2014, an estimated 60 ha of the dam was infested with Egeria densa, which can spread at a rate of 50% per annum under optimal conditions. E. densa limits access to, and the recreational use of, the dam. We use the travel cost method to estimate the recreational value of the Midmar Dam, informing the maximum desirable cost of control. The model estimates that the most likely extent of the invasion would be between 233 ha and 771 ha. The estimated cumulative NPV is R684 million for the best-case scenario, which allows for clearing operations and a spread rate of 15%. If no clearing is done, the cumulative NPV is reduced to an estimated -R20 million. This study therefore suggests that management of the problem is imperative, but that control efforts should not exceed R687.8 million over 30 years. Doing so will constitute a net loss to society.
Prediction and error in multi-stage models for spread of aquatic non-indigenous species
Food Chemistry, 2011
Aim Predictions of spread of non-indigenous species allow for greater efficiency in managing invasions by targeting areas for preventative measures. The invasion sequence is a useful concept in predictions of spread, as it allows us to test hypotheses about the transport and establishment of propagules in novel habitats. Our aims are twofold: (1) to develop and validate multi-stage invasion models for the introduced fishhook waterflea, Cercopagis pengoi, and (2) to assess how variability in the transport patterns of the propagules influences the accuracy and spatial extent for predictions of spread.Location New York State, USA.Methods We developed a two-stage model for the spread of C. pengoi. First, we developed a stochastic gravity model for dispersal based on surveys of recreational boat traffic in New York State as a proxy for propagule pressure. We then modelled the probability of establishment based on predicted levels of propagule pressure and measures of lakes’ physicochemistry. In addition, we used Monte Carlo simulations based on the gravity model to propagate variability in boater traffic through the establishment model to assess how uncertainty in dispersal influenced predictions of spread.Results The amount recreationalists were willing to spend, lake area and population size of the city nearest to the destination lake were significant factors affecting boater traffic. In turn, boater traffic, lake area, specific conductance and turbidity were significant predictors of establishment. The inclusion of stochastic dispersal reduced the rate of false positives (i.e. incorrect prediction of an invasion) in detecting invasions at the upper 95% prediction interval for the probability of establishment.Main conclusions Combinations of measures of propagule pressure, habitat suitability and stochastic dispersal allow for the most accurate predictions of spread. Further, multi-stage spread models may overestimate the extent of spread if stochasticity in early stages of the models is not considered.
Aquatic Invasions, 2014
This year-long study, covering three main seasons of India, focused on enumerating the effect of varying cover of Alternanthera philoxeroides (alligator weed) on the associated macrophyte species diversity of the littoral region of natural pond ecosystem. A total of 192 quadrats were randomly placed in the littoral region of 12 similar ponds containing varying degrees of A. philoxeroides infestation to estimate A. philoxeroides 'cover (%)' and number of associated macrophyte species in each quadrat. Overall, 20 associated macrophyte species, including 16 aquatic/ littoral-associated, 2 non-aquatic species, and grasses and sedges, were found to be present. A. philoxeroides infestation was categorized into 4 cover grades (Grade I-IV) from lowest (no/negligible: <10% cover) to highest (>60% cover). For each season, significant differences in the total number of associated macrophyte species across the 4 A. philoxeroides cover grades were found. A Poisson-regression model showed that for each season, even when the effect of other invasive species was adjusted, the number of associated native macrophyte species in a quadrat decreases significantly with increase in A. philoxeroides cover. A comparison of the quadrat communities between the lowest grade (Grade I) and highest grade (Grade IV) of A. philoxeroides infestation showed a significant reduction of species richness, diversity and evenness from the lowest to the highest infestation grades. Again, Mann-Whitney U tests further revealed that the number of native macrophyte species was significantly lower at highest (Grade IV) A. philoxeroides infestation than that at lowest infestation (Grade I). The presence of multiple invaders in A. philoxeroides infested aquatic ecosystems is also reported, indicating probable facilitative interactions between A. philoxeroides and other invasive species. The socio-economic valuation of some important native plants, which were found to be significantly reduced at high infestation levels of A. philoxeroides, has also been highlighted.