Increase In Urban Cover Research Articles

Assessment of Urban Expansion and Identification of Sprawl Through Delineation of Urban Core Boundary

Abstract Cities are spatially expanding rapidly, leading to urban sprawl. This study aims to understand the nature of the urban expansion of Chennai city, located on India’s southeastern coast, by determining the urban growth pattern and identifying the urban sprawl areas. The urban growth pattern and sprawl areas between 1998 and 2019 are identified using remote sensing data through the delineation of the Urban Core Boundary (UCB). The urban areas were extracted from the Land Use Land Cover (LULC) classification using combined classification technique to delineate the UCB. All the findings were validated using ground truth information. LULC classification performed with an accuracy of more than 90 % for urban land cover revealed an increase in urban cover by 71.77% from 1998 to 2009 and 36.91 % from 2009 to 2019. The delineated UCB’s peripheral distance was measured from the city centre in an anticlockwise direction from 0˚ to 360˚ at every 10˚ interval. It is observed that the urban core boundary expanded to a maximum of 16.02 km along 240˚ and 11.93 km along 220˚ from the city centre, and the lands in the vicinity of the National Highway (NH 32), which is situated between these sectors, experienced maximum urban development. The study also pinpointed the sprawl areas during the study period, revealing that the urban sprawl occurs along the highways, around designated special economic zones, and industrial corridors.

Flying insect biomass is negatively associated with urban cover in surrounding landscapes

AbstractAimIn this study, we assessed the importance of local‐ to landscape‐scale effects of land cover and land use on flying insect biomass.LocationDenmark and parts of Germany.MethodsWe used rooftop‐mounted car nets in a citizen science project (“InsectMobile”) to allow for large‐scale geographic sampling of flying insects. Volunteers sampled insects along 278 five‐km routes in urban, farmland, grassland, wetland and forest landscapes in the summer of 2018. The bulk insect samples were dried overnight to obtain the sample biomass. We extracted proportional land use variables in buffers between 50 and 1,000 m along the routes and compiled them into land cover categories to examine the effect of each land cover, and specific land use types, on insect biomass.ResultsWe found a negative association between urban cover and flying insect biomass (1% increase in urban cover = 1% [95% CI: −3.0 to 0.0] decrease in biomass in Denmark, and a 3% [95% CI: −3.0 to 0.0] decrease in Germany) at a landscape scale (1,000‐m buffer). In Denmark, we also found positive effects of semi‐natural land cover types, that is protected grassland (largest at the landscape scale, 1000 m) and forests (largest at intermediate scales, 250 m). Protected grassland cover had a stronger positive effect on insect biomass than forest cover did. For farmland cover, the positive association with insect biomass was not clearly modified by any variable associated with farmland use intensity. The negative association between insect biomass and urban land cover appeared to be reduced by increased urban green space.Main conclusionsOur results show that land cover has an impact on flying insect biomass with the magnitude of this effect varying across spatial scales. However, the vast expanse of grey space in urbanized areas has a direct negative impact on flying insect biomass across all spatial scales examined.

Urban sprawl into Natura 2000 network over Europe.

Urban growth is a major threat to biodiversity conservation at the global scale. Its impacts are expected to be especially detrimental when it sprawls into the landscape and reaches sites of high conservation value due to the species and ecosystems they host, such as protected areas. I analyzed the degree of urbanization (i.e., urban cover and growth rate) from 2006 to 2015 in protected sites in the Natura 2000 network, which, according to the Habitats and Birds Directives, harbor species and habitats of high conservation concern in Europe. I used data on the degree of land imperviousness from COPERNICUS to calculate and compare urban covers and growth rates inside and outside Natura 2000. I also analyzed the relationships of urban cover and growth rates with a set of characteristics of Natura sites. Urban cover inside Natura 2000 was 10 times lower than outside (0.4% vs. 4%) throughout the European Union. However, the rates of urban growth were slightly higher inside than outside Natura 2000 (4.8% vs. 3.9%), which indicates an incipient urban sprawl inside the network. In general, Natura sites affected most by urbanization were those surrounded by densely populated areas (i.e., urban clusters) that had a low number of species or habitats of conservation concern, albeit some member states had high urban cover or growth rate or both in protected sites with a large number of species or habitats of high conservation value. Small Natura sites had more urban cover than large sites, but urban growth rates were highest in large Natura sites. Natura 2000 is protected against urbanization to some extent, but there is room for improvement. Member states must enact stricter legal protection and control law enforcement to halt urban sprawl into protected areas under the greatest pressure from urban sprawl (i.e., close to urban clusters). Such actions are particularly needed in Natura sites with high urban cover and growth rates and areas where urbanization is affecting small Natura sites of high conservation value, which are especially vulnerable and concentrated in the Mediterranean region.

More losses than gains in ground-nesting bees over 60 years of urbanization

Along with agricultural intensification, urbanization is often implicated in bee declines worldwide. While the vast majority of studies investigate how bee assemblages respond to urbanization across different spatial scales, very few attempts have used a temporal comparison to evaluate the impact of urbanization. The city of Curitiba in southern Brazil is unique for having long-term data of bees, and thus is a good model for studying urban temporal changes. The main goal of this study is to investigate how a ground-nesting assemblage responded to six decades of urban growth in Curitiba. In this time lapse the city population grew from 140 thousand to almost 2 million inhabitants. We demonstrate a 94% decline in nest abundance, a 35% decline in species richness, and a 24% decline in phylogenetic diversity from 1955 (T1) to 2018 (T2). Temporal beta diversity values between T1 and T2 were very high and most sampling sites were dominated by losses in nest abundance. All sampling sites changed similarly with losses in nesting substrates (i.e. exposed soil) and a substantial increase in surrounding impervious surface. This study exhibits how depletion of nesting substrates combined with increases in urban cover can affect pollinators, a concerning scenario as most bees nest in friable soil and thus are strongly susceptible to urbanization. We emphasize that urban planning policies to protect ground-nesting bees are essential to preserve the important ecological service of pollination in cities.

Land use/land cover change and land surface temperature of Ibadan and environs, Nigeria.

Rapid urbanization is having a considerable impact on various aspects of living, thereby altering the biophysical environment. This study adopted the use of remote sensing technique and geographical information system (GIS) to analyse the relationship between changing land use/land cover and land surface temperature in a rapidly urbanizing tropical cityof Ibadan between 1984 and 2019. Landsat series TM, ETM+, and OLI satellite imageries of Ibadan region city for 1984, 2002, and 2019, respectively, were obtained from the US Geological Survey (USGS) Landsat series of Earth Observation satellites accessible on the Google earth engine (GEE) platform. Supervised classification was done using a random forest (RF) machine learning classifier in the GEE platform. Surface emissivity maps were obtained from the normalized difference vegetation index (NDVI) thresholds method and land cover information. The surface emissivity based on NDVI classes was used to retrieve land surface temperature (LST). The results showed an increase in urban cover from 341.72km2 in 1984 to 520.58km2 in 2019 with an average increase in land surface temperature from 17°C to 38°C, respectively. Temperature sampling in the north-south and west-east transect revealed that highly urbanized areas located at the city centre of Ibadan have the highest LST of about 38°C. It dissipates to about 19°C at the suburb that is less built up. A significant negative relationship exists between the health condition of vegetation (NDVI) and LST with a correlation coefficient of r = - 0.95. The study confirms the potential application of GIS and remote sensing for detecting urban growth as well as relates growth impact to LST, thereby suggesting that fitting strategies will be important for the sustainable management of the urban areas.

Local and Landscape Drivers of Parasitoid Abundance, Richness, and Composition in Urban Gardens.

Urbanization negatively affects biodiversity, yet some urban habitat features can support diversity. Parasitoid wasps, an abundant and highly diverse group of arthropods, can inhabit urban areas and do well in areas with higher host abundance, floral resources, or local or landscape complexity. Parasitoids provide biological control services in many agricultural habitats, yet few studies have examined diversity and abundance of parasitoids in urban agroecosystems to understand how to promote conservation and function. We examined the local habitat and landscape drivers of parasitoid abundance, superfamily and family richness, and parasitoid composition in urban gardens in the California central coast. Local factors included garden size, ground cover type, herbaceous plant species, and number of trees and shrubs. Landscape characteristics included land cover and landscape diversity around gardens. We found that garden size, mulch cover, and urban cover within 500 m of gardens predicted increases in parasitoid abundance within gardens. The height of herbaceous vegetation and tree and shrub richness predicted increases in superfamily and family richness whereas increases in urban cover resulted in declines in parasitoid richness. Abundance of individual superfamilies and families responded to a wide array of local and landscape factors, sometimes in opposite ways. Composition of parasitoid communities responded to changes in garden size, herbaceous plant cover, and number of flowers. Thus, both local scale management and landscape planning may impact the abundance, diversity, and community composition of parasitoids in urban gardens, and may result in differences in the effectiveness of parasitoids in biological control.

Loss rates of butterfly species with urban development. A test of atlas data and sampling artefacts at a fine scale

Data for the United Kingdom (UK) Manchester Butterfly Atlas produced conflicting species loss rates for increased urban development. In particular, a very low rate of loss was recorded (0.19 species for every 10% increase in urban cover) for the Mersey Valley mapped at a high resolution of 1 ha units. It was suggested that sampling artefacts (uneven recording) or failure to distinguish vagrant individuals from breeding populations cause this. Herein, results are reported for 30 sample squares, within the Mersey Valley, surveyed uniformly throughout 1999. It is shown that loss rates are as high as areas mapped at lower resolution over wider areas (0.67–0.68 species for every 10% increase in urban cover) and that increasingly stringent definitions of urban cover result in higher loss rates. Comparison with the data from the Atlas, but for the same 30 sample squares, indicate that the low rates at a fine scale for the complete Atlas data are more likely to be caused by uneven recording than from failure to record species status. However, progressive sampling of squares, despite uniform recording, will inevitably cause a reduction in loss rates of total species for increases in urban development.

Potential Roadside Biases Due to Habitat Changes along Breeding Bird Survey Routes

Breeding Bird Surveys (BBS) are conducted along roadside routes to enable a large geographic area to be surveyed. Yet the potential biases of sampling populations only from roadsides have received little attention. We sampled aerial photography of BBS routes taken in the mid-1960s and late-1980s to evaluate whether habitat changes that occurred along roadsides were also occurring in the surrounding area, and whether the frequency of habitats encountered along roadsides were similar to that off-route. We examined 28 routes in Maryland and 25 routes in Ohio, and defined roadside area as within 200 m of the road, and off-route as 200-1,600 m from the road. Most habitat changes that occurred along BBS roadsides also were occurring in the off-route areas. However, increases in urban cover were significantly greater along the road in Maryland where urbanization of farmland was the predominant habitat change. The small increase in urban cover in Ohio was not significantly greater along the road. Construction of single family homes was greater along BBS roadsides in both states. In Ohio, the greatest change in habitat was the conversion of farmland back to forest, which was not significantly greater along the road. Changes associated with urbanization were more biased towards roadsides than the reforestation of farmland. Within one time period, roadside areas had less forest and more agricultural and urban cover types than occurred off-route.

The impact of urban development on butterflies within a city region

The effect of urban development on butterfly species' richness and species' incidence is tested for the Greater Manchester conurbation and two sample areas, mapped at finer scales, within the southern part of the conurbation. The tests include measures of bias for recording effort (number of visits). Species' richness is found to increase with percentage urban cover for Greater Manchester (tetrad scale) and decrease with urban cover for the two sample areas in South West Manchester (1 km scale) and the Mersey Valley (100 m scale). For Greater Manchester, the increase in species' richness with increased urban cover is largely explained by lower species' richness at higher altitude in the Pennines bounding the conurbation. For the two sample areas, decreasing species' richness associated with increasing urban cover corresponds with reductions in the areas of a number of semi-natural habitats, hostplants and nectar sources. Despite these statistically significant correlations, the impact of urban cover on species' richness is weak. The maximum loss rate identified anywhere within the region is 0.81 species per 10% change in urban cover for South West Manchester. This finding may reflect on the generally low species diversity of the region. However, these results could be influenced by recording and sampling artefacts, particularly the failure of mapping programmes to distinguish vagrant individuals from breeding populations and a bias of records to vagrants. This is supported by the higher correlations between species' incidence and nectar sources than between species' incidence and their hostplants. Adult butterflies are opportunistic nectar users and nectar sources are more widely spread and thus less influenced by urban development than are specific butterfly hostplants. The finding may also reflect on the capacity of most of the butterfly species to breed successfully on tiny areas of hostplant existing within extensively built-up areas. Moreover, the capacity of butterfly species to persist by using small fragments of hostplants would be enhanced by vagrancy. If this is indeed the case, it is a finding that would support the value of small patches in butterfly metapopulations, albeit ones comprising incomplete complements of resources required during the life cycle. The incidence of most species decreases with increase in urban cover. Multivariate analyses indicate that this is owing to corresponding declines in hostplant-habitats and nectar sources. Five species increase with urban cover, but none attain formal significance. Associations among hostplants and habitat variables in a principal components analysis suggest that, in three cases (Pieris brassicae, P. rapae, Celastrina argiolus), this is owing to increasing areas of their hostplants within urban environments.