Linking land system changes (1980–2017) with the trophic status of an urban wetland: Implications for wetland management

Variability in the response of Baumea articulata and Typha orientalis to water regime was assessed at eight urban wetland lakes on the Swan Coastal Plain, south-western Australia. Distribution, productivity and reproduction along water regime gradients were assessed, and the importance of wetland nutrient status in altering plant response to water regime was also considered. The overall range in distribution observed across the lakes was similar for both species, but there was significant between-lake variation in distribution relative to mean water depth. Neither species occupied its full 'potential' distribution range, relative to water regime, at any one wetland. Standing biomass and ramet and inflorescence densities varied along the water regime gradient, with peak values generally occurring at intermediate water depths. There was a shift in phenology (ramet emergence, new leaf growth, flowering and seed production) with increasing mean water depth and nutrient status. Seasonal values of aboveground productivity changed along the water regime gradient for both species. Comparison of productivity at sampling points of different nutrlent status but similar water regime showed a significantly greater growth response in T. orientalis compared with B. articulata. The significance of these results to urban wetland management is discussed.

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Evaluation of Various DEMs for Quantifying Soil Erosion Under Changing Land Use and Land Cover in the Himalaya

Frontiers in Earth Science ◽

10.3389/feart.2021.782128 ◽

2021 ◽

Vol 9 ◽

Author(s):

Shakil Ahmad Romshoo ◽

Aazim Yousuf ◽

Sadaff Altaf ◽

Muzamil Amin

Keyword(s):

Land Use ◽

Soil Erosion ◽

Land Cover ◽

Water Conservation ◽

Thermal Emission ◽

Rainfall Erosivity ◽

Kashmir Himalaya ◽

Land System ◽

System Changes ◽

Steep Slopes

Soil erosion is one of the serious environmental threats in the Himalayas, primarily exacerbated by the steep slopes, active tectonics, deforestation, and land system changes. The Revised Universal Soil Loss Equation was employed to quantify soil erosion from the Vishav watershed in the Kashmir Himalaya, India. Topography and land use/land cover (LULC) are important driving factors for soil erosion. Most often, a Digital Elevation Model (DEM) is used in erosion models without any evaluation and testing which sometimes leads to erroneous estimates of soil erosion. For the best topographic characterization of the watershed, four publicly available DEMs with almost identical resolution (∼30 m), were evaluated. The DEMs were compared with GPS measurements to determine the most reliable among the tested DEMs for soil erosion estimation. Statistical evaluation of the DEMs with GPS data indicated that the CARTO DEM is better with root mean square error (RMSE) of 18.2 m than the other three tested DEMs viz., Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), Shuttle Radar Topography Mission (SRTM), and Advanced Land Observing Satellite (ALOS). Slope length and slope steepness factors were computed from the DEMs. Crop cover and management factors were generated from the satellite-derived LULC. Moreover, rainfall data of the nearest stations were used to compute rainfall erosivity and soil erodibility factor was derived from the soil texture data generated from 375 soil samples. The simulated erosion estimates from SRTM, ALOS, and CARTO DEMs showed similar spatial patterns contrary to the ASTER estimates which showed somewhat different patterns and magnitude. The mean erosion in the study area has almost doubled from 2.3 × 106 tons in 1981 to 4.6 × 106 tons in 2019 mainly driven by the anthropogenic LULC changes. The increased soil erosion is due to the degradation of forest cover, urbanization, steep slopes, and land system changes observed during the period. In absence of the observations, the simulated soil erosion was validated with the land degradation map of the watershed which showed a good correspondence. It is hoped that the results from this work would inform policymaking on soil and water conservation measures in the data-scarce mountainous Kashmir Himalaya.

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Governing the urban wetlands: a multiple case-study of policy, institutions and reference points

Environmental Conservation ◽

10.1017/s0376892913000519 ◽

2013 ◽

Vol 41 (3) ◽

pp. 276-289 ◽

Cited By ~ 5

Author(s):

MISSAKA HETTIARACHCHI ◽

CLIVE McALPINE ◽

T. H. MORRISON

Keyword(s):

Policy Evaluation ◽

Wetland Management ◽

Regional Scale ◽

Reference Points ◽

Environmental Research ◽

Urban Wetlands ◽

Policy Regimes ◽

Multiple Case ◽

Urban Wetland ◽

Wetland Policy

SUMMARYWorldwide, coastal and floodplain wetlands are rapidly urbanizing, making them highly vulnerable to biodiversity loss, biological invasion and climate change. Yet urban wetlands management is an understudied area of global environmental research. Different policy approaches and institutional arrangements in place for urban wetlands governance have to be studied comparatively to obtain a better understanding of the current issues. This paper investigates four urban wetland policy regimes and the application of ecological reference points across four countries. The regimes are discussed within the context of global policy trends, urbanization patterns and environmental change. The analysis illustrates that the four cases deviate substantially in certain characteristics and converge in others. Global trends such as environmental treaties and restructuring of city spaces are common policy drivers for all cases. Conversely, the localized specific problems have yielded specialized policy responses in each case. Declaration of fixed biological reference points for wetlands were not used at any stage of the policy development process. However, the wetland managers formally or informally set up ecosystem-services oriented benchmarks for urban wetland management. Globally-applicable normative policy directives or universal ecological reference points seem bound to fail in urban wetlands governance. However, in designing effective urban wetland policy and institutions at the regional scale, both context-specific and generalized lessons from empirical policy evaluation of multiple case studies need to be jointly considered. Based on the characteristics of the policy regimes analysed in this study, a hypothetical framework for urban wetland policy evaluation is proposed; this has yet to be validated by empirical application to actual cases.

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Examining the competing effects of contemporary land management vs. land cover changes on global air quality

Atmospheric Chemistry and Physics ◽

10.5194/acp-21-16479-2021 ◽

2021 ◽

Vol 21 (21) ◽

pp. 16479-16497

Author(s):

Anthony Y. H. Wong ◽

Jeffrey A. Geddes

Keyword(s):

Air Quality ◽

Land Cover ◽

Dry Deposition ◽

Surface Ozone ◽

Land Cover Changes ◽

Land System ◽

Time Period ◽

System Changes ◽

Emission Changes ◽

Surface O3

Abstract. Our work explores the impact of two important dimensions of land system changes, land use and land cover change (LULCC) as well as direct agricultural reactive nitrogen (Nr) emissions from soils, on ozone (O3) and fine particulate matter (PM2.5) in terms of air quality over contemporary (1992 to 2014) timescales. We account for LULCC and agricultural Nr emissions changes with consistent remote sensing products and new global emission inventories respectively estimating their impacts on global surface O3 and PM2.5 concentrations as well as Nr deposition using the GEOS-Chem global chemical transport model. Over this time period, our model results show that agricultural Nr emission changes cause a reduction of annual mean PM2.5 levels over Europe and northern Asia (up to −2.1 µg m−3) while increasing PM2.5 levels in India, China and the eastern US (up to +3.5 µg m−3). Land cover changes induce small reductions in PM2.5 (up to −0.7 µg m−3) over Amazonia, China and India due to reduced biogenic volatile organic compound (BVOC) emissions and enhanced deposition of aerosol precursor gases (e.g., NO2, SO2). Agricultural Nr emission changes only lead to minor changes (up to ±0.6 ppbv) in annual mean surface O3 levels, mainly over China, India and Myanmar. Meanwhile, our model result suggests a stronger impact of LULCC on surface O3 over the time period across South America; the combination of changes in dry deposition and isoprene emissions results in −0.8 to +1.2 ppbv surface ozone changes. The enhancement of dry deposition reduces the surface ozone level (up to −1 ppbv) over southern China, the eastern US and central Africa. The enhancement of soil NO emission due to crop expansion also contributes to surface ozone changes (up to +0.6 ppbv) over sub-Saharan Africa. In certain regions, the combined effects of LULCC and agricultural Nr emission changes on O3 and PM2.5 air quality can be comparable (>20 %) to anthropogenic emission changes over the same time period. Finally, we calculate that the increase in global agricultural Nr emissions leads to a net increase in global land area (+3.67×106km2) that potentially faces exceedance of the critical Nr load (>5 kg N ha−1 yr−1). Our result demonstrates the impacts of contemporary LULCC and agricultural Nr emission changes on PM2.5 and O3 in terms of air quality, as well as the importance of land system changes for air quality over multidecadal timescales.

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