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	<title>landscape fragmentation &#8211; Science</title>
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	<title>landscape fragmentation &#8211; Science</title>
	<link>https://scienmag.com</link>
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		<title>Bare Ground Before the City: Ibadan&#8217;s Predictable Path of Urban Expansion</title>
		<link>https://scienmag.com/bare-ground-before-the-city-ibadans-predictable-path-of-urban-expansion/</link>
		
		<dc:creator><![CDATA[Violet Maxwell]]></dc:creator>
		<pubDate>Fri, 02 Oct 2026 04:22:28 +0000</pubDate>
				<category><![CDATA[Earth Science]]></category>
		<category><![CDATA[CA-Markov model]]></category>
		<category><![CDATA[city growth prediction Ibadan]]></category>
		<category><![CDATA[forest to urban land conversion]]></category>
		<category><![CDATA[future urban landscape Nigeria]]></category>
		<category><![CDATA[human-environment interaction Nigeria]]></category>
		<category><![CDATA[Ibadan]]></category>
		<category><![CDATA[land change sequence Nigeria]]></category>
		<category><![CDATA[land planning and sustainability]]></category>
		<category><![CDATA[land transformation in Ibadan]]></category>
		<category><![CDATA[land transformation research]]></category>
		<category><![CDATA[land use change]]></category>
		<category><![CDATA[land use change studies]]></category>
		<category><![CDATA[Landsat]]></category>
		<category><![CDATA[landscape fragmentation]]></category>
		<category><![CDATA[Nigeria]]></category>
		<category><![CDATA[path dependency]]></category>
		<category><![CDATA[peri-urban transformation]]></category>
		<category><![CDATA[remote sensing]]></category>
		<category><![CDATA[Sankey diagram]]></category>
		<category><![CDATA[satellite analysis of African cities]]></category>
		<category><![CDATA[structured urban development processes]]></category>
		<category><![CDATA[sub-Saharan Africa]]></category>
		<category><![CDATA[urban expansion]]></category>
		<guid isPermaLink="false">https://scienmag.com/?p=225666</guid>

					<description><![CDATA[A two-decade satellite analysis of Ibadan's peri-urban corridor reveals that urban expansion follows a predictable sequence from vegetation to bare land to built-up, offering planners a critical intervention window before concrete sets.]]></description>
										<content:encoded><![CDATA[<p>On the eastern fringe of Ibadan, one of Africa&#8217;s largest indigenous metropolitan areas, the landscape is telling a story in stages. First the trees and farmland disappear, leaving bare, cleared ground. Then, a decade or so later, the concrete arrives. That two-step sequence, rather than a single leap from vegetation to city, is the central finding of a new study published in Discover Geoscience, which tracked two decades of land transformation across the Akinyele, Lagelu and Egbeda corridor of southwestern Nigeria and projected what the region will look like by 2050.</p>
<p>The research, led by Remilekun Olaide Olaiya of Tai Solarin Federal University of Education and Olayinka Akinsumbo Ajala of Obafemi Awolowo University, challenges the way scientists and planners usually think about urban growth. Most land-change studies treat each conversion as an independent event: a forest becomes a suburb, a farm becomes a road. But the Ibadan evidence points to something more structured, a path-dependent process in which the state of the land today shapes what it becomes tomorrow. In this framing, bare land is not a dead end or a stable category. It is a waiting room.</p>
<p>To uncover that sequence, the team assembled a remarkable satellite record. Using cloud-free dry-season imagery from four different Landsat sensors, Landsat 7 in 2005, Landsat 5 in 2010, Landsat 8 in 2015 and Landsat 9 in 2025, all at 30-metre resolution, they classified the landscape into four categories: built-up area, bare land, vegetation and water. The images were carefully pre-processed, converted to top-of-atmosphere reflectance and atmospherically corrected with the Dark Object Subtraction method, so that differences between sensors and years could not masquerade as genuine change. Ground-truthing combined a 2025 field survey of 180 points recorded with handheld GNSS receivers and historical high-resolution Google Earth imagery for the earlier epochs.</p>
<p>The numbers are striking. In 2005, vegetation covered 688 square kilometres, more than two-thirds of the corridor, while built-up land occupied just 87.3 square kilometres, or 8.39 percent. By 2015, the picture had flipped dramatically: bare land had surged to 484 square kilometres, becoming the dominant class, while vegetation had lost nearly half its extent. Built-up land had more than doubled to 199.5 square kilometres. Then, between 2015 and 2025, the pattern reversed again. Bare land shrank by 215.9 square kilometres as built-up land climbed to 373 square kilometres, 35.83 percent of the corridor. Land that had been cleared in the first decade was being paved over in the second.</p>
<p>The sequencing becomes unmistakable when the transition matrices are visualised as Sankey flow diagrams, where the width of each link is proportional to the area converted. The single largest flow was vegetation to bare land, 333.5 square kilometres, followed by bare land to built-up land at 173.5 square kilometres. Direct vegetation-to-built-up conversion, the pathway most studies implicitly assume, accounted for only 112.2 square kilometres. Meanwhile, built-up land showed complete persistence: every square kilometre urban in 2005 was still urban in 2025. Cities, once established, do not give land back.</p>
<p>The spatial pattern reinforced the temporal one. Kernel density hotspot analysis, which converts newly built-up pixels into a continuous surface of growth intensity, showed that between 2005 and 2015 the hottest expansion zones were confined to Lagelu and southern Egbeda, while most of Akinyele remained quiet. In the following decade, very-high-intensity hotspots spread across Lagelu and Egbeda and pushed into Akinyele, reflecting infilling and densification of previously cleared ground. The result is a pronounced south-to-north urbanisation gradient, with growth radiating from the existing core along major transport corridors, a pattern familiar from other rapidly expanding African metropolitan fringes.</p>
<p>The ecological cost is measured not only in lost hectares but in shattered habitat structure. Using morphological spatial pattern analysis, the researchers found that the number of core vegetation patches, large intact habitat areas, collapsed from 82 to 21 over the study period. Total core area fell from 482.8 to 132.6 square kilometres, mean patch size dropped from 6.42 to 1.58 square kilometres, and the Landscape Shape Index, a measure of edge complexity, nearly doubled from 14.62 to 27.34. Patch density more than doubled. In plain terms, what remains of the corridor&#8217;s vegetation is increasingly chopped into small, isolated, edge-exposed fragments, a condition that ecologists consider a more sensitive indicator of stress than raw area loss alone.</p>
<p>What happens next depends on whether recent history repeats itself, and the team built a model to test exactly that. They coupled a first-order Markov chain, which estimates the probability of each land class converting into every other class, with a cellular automata component that allocates change spatially using a 5-by-5 contiguity filter, so that new growth clusters next to existing development. Consolidated built-up cells were treated as absorbing states, physically barred from reverting. Before projecting forward, the model was hindcast: calibrated on 2005 to 2015 data and asked to simulate 2025, then compared cell by cell against the independently classified 2025 map. It scored a standard Kappa of 0.89 and a Figure of Merit of 0.36, figures consistent with the best-performing land-change models in the literature.</p>
<p>Run forward to 2050, the validated model delivers a sobering scenario. Built-up land is projected to reach approximately 580 square kilometres, up from 373 in 2025, while vegetation declines to 198.3 square kilometres, less than a third of its 2005 extent. Bare land continues its role as the conveyor belt, progressively converted to urban uses as the vegetation reservoir shrinks. The Vegetation-to-Bare-Land-to-Built-up sequence persists through the projection rather than giving way to direct conversion, echoing findings from Greater Cairo and other rapidly urbanising Global South landscapes, and aligning with United Nations projections that Africa will experience the fastest urban growth on Earth through mid-century.</p>
<p>The policy implications may be the study&#8217;s most valuable contribution. Because land clearing reliably precedes construction, the bare-land stage represents a critical and identifiable intervention window. During the vegetation stage, the authors argue, planners should prioritise conservation zoning, urban growth boundaries and enforcement of statutory plans. Once land is cleared, development control, land banking and time-bound permits can regulate speculation before concrete sets. After build-out, the focus shifts to infill, densification and transit-oriented development. The authors caution that their projection is a conditional continuation scenario, not a deterministic forecast, and that the model does not capture future policy shifts, economic shocks or the fine-scale informal development that 30-metre pixels cannot resolve. But the core message stands: peri-urban transformation is not a roll of the dice. It is a sequence with recognisable stages, and the moment to steer it is while the ground is still bare.</p>
<p><strong>Subject of Research:</strong> Path-dependent peri-urban land transformation and simulated urban expansion to 2050 in the Ibadan corridor, Nigeria</p>
<p><strong>Article Title:</strong> Path dependent peri urban land transformation and urban expansion in Ibadan Nigeria</p>
<p><strong>Article References:</strong> Olaiya, R. O., &amp; Ajala, O. A. (2026). Path dependent peri urban land transformation and urban expansion in Ibadan Nigeria. <em>Discover Geoscience, 4</em>(1), Article 381. <a href="https://doi.org/10.1007/s44288-026-00749-2" rel="noopener noreferrer">https://doi.org/10.1007/s44288-026-00749-2</a></p>
<p><strong>Image Credits:</strong> AI Generated</p>
<p><strong>DOI:</strong> <a href="https://doi.org/10.1007/s44288-026-00749-2" rel="noopener noreferrer">10.1007/s44288-026-00749-2</a></p>
<p><strong>Keywords:</strong> peri-urban transformation, urban expansion, Ibadan, Nigeria, Landsat, land-use change, CA-Markov model, Sankey diagram, landscape fragmentation, remote sensing, path dependency, Sub-Saharan Africa</p>
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		<post-id xmlns="com-wordpress:feed-additions:1">225666</post-id>	</item>
		<item>
		<title>Wetlands on a Border: Satellites Track 25 Years of Fragmentation at Xingkai Lake</title>
		<link>https://scienmag.com/wetlands-on-a-border-satellites-track-25-years-of-fragmentation-at-xingkai-lake/</link>
		
		<dc:creator><![CDATA[Gavin Prescott]]></dc:creator>
		<pubDate>Thu, 01 Oct 2026 08:06:06 +0000</pubDate>
				<category><![CDATA[Earth Science]]></category>
		<category><![CDATA[Cross-border environmental management]]></category>
		<category><![CDATA[ecological connectivity]]></category>
		<category><![CDATA[Ecological connectivity decline]]></category>
		<category><![CDATA[Impact of habitat loss on biodiversity]]></category>
		<category><![CDATA[Land use change in Northeast Asia]]></category>
		<category><![CDATA[land-cover change]]></category>
		<category><![CDATA[landscape fragmentation]]></category>
		<category><![CDATA[machine learning in environmental monitoring]]></category>
		<category><![CDATA[Markov–cellular automata]]></category>
		<category><![CDATA[Random Forest]]></category>
		<category><![CDATA[remote sensing]]></category>
		<category><![CDATA[Satellite land cover mapping]]></category>
		<category><![CDATA[Scenario modeling for wetland futures]]></category>
		<category><![CDATA[scenario simulation]]></category>
		<category><![CDATA[SHAP]]></category>
		<category><![CDATA[transboundary conservation]]></category>
		<category><![CDATA[Transboundary freshwater ecosystems]]></category>
		<category><![CDATA[Wetland ecosystem degradation]]></category>
		<category><![CDATA[Wetland fragmentation analysis]]></category>
		<category><![CDATA[wetland loss]]></category>
		<category><![CDATA[Wetlands conservation]]></category>
		<category><![CDATA[XGBoost]]></category>
		<category><![CDATA[Xingkai Lake Basin]]></category>
		<category><![CDATA[Xingkai Lake ecology]]></category>
		<guid isPermaLink="false">https://scienmag.com/?p=221254</guid>

					<description><![CDATA[A 25-year satellite analysis of the China–Russia Xingkai Lake Basin reveals a 44.9 percent wetland loss, a 16.5 percent decline in structural ecological connectivity, and projects that ecological protection scenarios would deliver far better connectivity by 2050 than agricultural expansion.]]></description>
										<content:encoded><![CDATA[<p>Straddling the frontier between China and Russia in Northeast Asia, Xingkai Lake is the largest freshwater lake on the China–Russia border and the anchor of one of the region&#8217;s most ecologically significant wetland systems. A new study published in Environmental Monitoring and Assessment has now assembled the most detailed picture yet of how this transboundary basin has changed over a quarter of a century, and where it is likely headed. By combining satellite-based land cover mapping with machine learning, landscape ecology metrics, and scenario simulation, a team of Chinese researchers led by Rongyang Zhang and Zhenshan Xue of the Northeast Institute of Geography and Agroecology quantified both the loss of wetlands and, crucially, the erosion of the ecological connections that bind the remaining habitat patches together. Their findings carry a stark warning: between 2000 and 2025, wetland area in the basin declined by 44.9 percent, and the connectivity of the landscape fell by 16.5 percent at the basin scale.</p>
<p>The significance of connectivity loss is often underestimated in conservation debates that focus narrowly on how much habitat remains. Two landscapes can contain identical areas of wetland, yet if one is arranged as a few large, contiguous blocks and the other as scattered, isolated fragments, the second will support far fewer viable populations of plants and animals. Species that move seasonally between breeding and feeding grounds, or that require gene flow among subpopulations to remain genetically healthy, depend on the physical arrangement of habitat as much as its total extent. The Xingkai Lake Basin, with its mix of marshes, open water, cropland, and forest, is a textbook case of why structure matters. The study&#8217;s authors measured this structure using the integral index of connectivity, a graph-based metric that treats habitat patches as nodes and the links between them as edges, allowing ecologists to compute how readily organisms could theoretically move across a landscape.</p>
<p>To build the historical record, the team generated land cover maps from Landsat imagery using a random forest classifier, a widely used machine learning algorithm that labels each pixel by combining the votes of many decision trees trained on reference data. Landsat&#8217;s archive, freely available through platforms such as Google Earth Engine, provides a consistent multi-decadal record at a spatial resolution fine enough to resolve the patchwork of fields and marshes typical of the Sanjiang Plain region. The researchers characterized landscape configuration using standard metrics, including patch density, the largest patch index, edge density, and the cohesion index, which together describe whether habitat is consolidating into large blocks or splintering into small pieces. They then quantified structural ecological connectivity with the integral index of connectivity at a 500-meter link threshold, meaning that habitat patches within 500 meters of one another were considered functionally linked for the purposes of the analysis.</p>
<p>The results reveal a basin under pressure, but with strikingly different dynamics on either side of the border. On the Chinese side, conversions of wetland to cropland and wetland to open surface water were broadly comparable in magnitude, although total cropland area declined slightly, by 0.4 percent at the net level, suggesting a complex reshuffling of land uses rather than a single dominant driver. On the Russian side, cropland expanded by 48.8 percent, while the gross conversion of wetland to open surface water was more prominent. The authors are careful to note that this mapped wetland-to-water pathway may partly reflect hydrological variability and classification uncertainty rather than true, permanent conversion, a reminder that remote sensing of wetlands is inherently challenging because inundated areas expand and contract seasonally and interannually.</p>
<p>Beyond simply documenting change, the study asked which environmental and socioeconomic variables best explain where land cover transitions occurred. The team employed XGBoost, a scalable gradient-boosted tree algorithm, and then applied SHapley Additive exPlanations, a technique from explainable artificial intelligence that attributes the contribution of each input variable to each prediction. This combination allowed the researchers to move past the black-box criticism that often accompanies machine learning in environmental science. Their analysis showed that land cover transitions were associated with different combinations of topographic, climatic, and human-related variables across the border, meaning that the drivers of landscape change in the Chinese portion of the basin differ from those operating in the Russian portion. For conservation planners, this is a critical insight: a one-size-fits-all policy applied uniformly across the basin would fail to address the distinct pressures acting on each side of the boundary.</p>
<p>The connectivity numbers deserve particular attention. At the 500-meter threshold, the basin-scale integral index of connectivity declined from 0.1647 to 0.1376 over the 25-year study period, a 16.5 percent drop. This decline occurred alongside a reduction in core habitat area and an increase in the number of patches, the classic signature of fragmentation. As large wetland blocks are carved into smaller pieces, the interior habitat that many wetland-dependent species require shrinks disproportionately, while the amount of exposed edge grows. Edges bring altered microclimates, greater access for predators and invasive species, and proximity to agricultural runoff. Global research, including landmark work on habitat fragmentation published in Science Advances, has documented lasting ecological impacts of this process, and the Xingkai findings add a transboundary Asian case study to that growing body of evidence.</p>
<p>What makes the study especially valuable is its forward-looking component. Using a Markov–cellular automata framework, a modeling approach that combines transition probabilities estimated from historical change with spatial rules governing where change can occur, the researchers simulated four future scenarios for the basin through 2050. The scenarios ranged from agricultural expansion priorities to ecological protection priorities, bracketing the plausible policy space for the region. The outcome differences were substantial. Under the ecological protection scenario, the basin retained the largest wetland area and the largest core habitat, and achieved the highest projected connectivity, with an integral index of connectivity of 0.1528. Under the agricultural priority scenario, connectivity fell to 0.1299, meaning that ecological protection would deliver a connectivity outcome 17.6 percent higher than a future dominated by farmland expansion.</p>
<p>These projections arrive at a moment of heightened global concern about wetlands. Research published in Nature in 2023 estimated extensive wetland loss over the past three centuries worldwide, and the Xingkai Basin sits within the broader Sanjiang Plain, one of China&#8217;s most intensively reclaimed agricultural regions, where historical wetland conversion has been well documented. Xingkai Lake itself, the largest shallow lake in Northeast Asia, has shown signs of recent environmental degradation in paleolimnological records, with sediment cores revealing declining conditions in recent decades. Wetlands in the basin provide water purification, flood buffering, carbon storage, and habitat for migratory birds along East Asian flyways, so the erosion of their spatial integrity has consequences that extend well beyond the basin&#8217;s boundaries.</p>
<p>The transboundary dimension adds both complexity and opportunity. Ecological processes do not respect political borders, and a wetland corridor severed on one side of a boundary can undermine conservation investments on the other. Scholars of transboundary conservation have repeatedly emphasized that cross-boundary collaboration is a key piece of the conservation puzzle, and the Xingkai study provides exactly the kind of shared, quantitative evidence base that such collaboration requires. Because the drivers of change differ between the Chinese and Russian portions of the basin, coordinated management would need to pair wetland retention and core habitat protection on the Chinese side with attention to cropland expansion and hydrological variability on the Russian side. The authors highlight the need for coordinated wetland retention, core habitat protection, and sustainable land use management across the entire basin.</p>
<p>Methodologically, the study also offers a template for other regions. The pipeline it demonstrates, from cloud-based satellite classification through landscape metrics and graph-theoretic connectivity indices to explainable machine learning and scenario simulation, can be replicated in any transboundary basin where consistent satellite data exist. The explicit acknowledgment of classification uncertainty, particularly around wetland-to-water transitions, reflects good practice in remote sensing, where accuracy assessment and transparency about limitations are essential for credible change detection. As global frameworks for biodiversity conservation push countries toward spatially explicit targets, studies of this kind show how the tools of machine learning and landscape ecology can turn decades of satellite observations into actionable maps of where habitat must be protected, restored, and reconnected. For Xingkai Lake, the message is clear: the next 25 years will determine whether the basin&#8217;s wetlands remain a connected ecological network or dissolve into isolated fragments on two sides of an international line.</p>
<p><strong>Subject of Research:</strong> Land cover change and structural ecological connectivity in the transboundary China–Russia Xingkai Lake Basin</p>
<p><strong>Article Title:</strong> Historical evolution and future trends of land cover patterns and structural ecological connectivity in the China–Russia Xingkai Lake Basin</p>
<p><strong>Article References:</strong> Zhang, R., Tian, E., Zou, Y., Zheng, M., &amp; Xue, Z. (2026). Historical evolution and future trends of land cover patterns and structural ecological connectivity in the China–Russia Xingkai Lake Basin. <em>Environmental Monitoring and Assessment, 198</em>(10), Article 1130. <a href="https://doi.org/10.1007/s10661-026-15970-2" rel="noopener noreferrer">https://doi.org/10.1007/s10661-026-15970-2</a></p>
<p><strong>Image Credits:</strong> AI Generated</p>
<p><strong>DOI:</strong> <a href="https://doi.org/10.1007/s10661-026-15970-2" rel="noopener noreferrer">10.1007/s10661-026-15970-2</a></p>
<p><strong>Keywords:</strong> Xingkai Lake Basin, wetland loss, ecological connectivity, land cover change, landscape fragmentation, remote sensing, random forest, XGBoost, SHAP, Markov–cellular automata, transboundary conservation, scenario simulation</p>
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		<post-id xmlns="com-wordpress:feed-additions:1">221254</post-id>	</item>
		<item>
		<title>Satellites Reveal China&#8217;s Urban Waters Are Shrinking and Breaking Apart</title>
		<link>https://scienmag.com/satellites-reveal-chinas-urban-waters-are-shrinking-and-breaking-apart/</link>
		
		<dc:creator><![CDATA[Sloane Callahan]]></dc:creator>
		<pubDate>Thu, 01 Oct 2026 07:23:25 +0000</pubDate>
				<category><![CDATA[Climate]]></category>
		<category><![CDATA[Beijing–Tianjin–Hebei]]></category>
		<category><![CDATA[China]]></category>
		<category><![CDATA[China Beijing–Tianjin–Hebei water resources]]></category>
		<category><![CDATA[ecosystem connectivity]]></category>
		<category><![CDATA[effects of water scarcity on urban sustainability]]></category>
		<category><![CDATA[environmental monitoring with remote sensing]]></category>
		<category><![CDATA[impact of water loss on city ecosystems]]></category>
		<category><![CDATA[land-cover change]]></category>
		<category><![CDATA[landscape fragmentation]]></category>
		<category><![CDATA[long-term water trend analysis in China]]></category>
		<category><![CDATA[remote sensing]]></category>
		<category><![CDATA[satellite imagery and machine learning for environmental monitoring]]></category>
		<category><![CDATA[satellite remote sensing of water bodies]]></category>
		<category><![CDATA[SHAP]]></category>
		<category><![CDATA[shrinking urban lakes and rivers]]></category>
		<category><![CDATA[structural degradation of urban wetlands]]></category>
		<category><![CDATA[sustainable urban planning]]></category>
		<category><![CDATA[urban blue spaces]]></category>
		<category><![CDATA[Urban water decline]]></category>
		<category><![CDATA[urban water fragmentation]]></category>
		<category><![CDATA[Urbanization]]></category>
		<category><![CDATA[water resources]]></category>
		<category><![CDATA[water stress in Chinese cities]]></category>
		<category><![CDATA[XGBoost]]></category>
		<guid isPermaLink="false">https://scienmag.com/?p=221094</guid>

					<description><![CDATA[A 24-year satellite analysis of the Beijing–Tianjin–Hebei region shows urban blue spaces shrinking and fragmenting, with population and vegetation factors outweighing climate and policy as drivers.]]></description>
										<content:encoded><![CDATA[<p>Across one of the world&#8217;s most water-stressed urban corridors, the lakes, rivers, ponds and wetlands that thread through its cities have been quietly disappearing for more than two decades. A new remote-sensing study of the Beijing–Tianjin–Hebei (BTH) region, published in Environmental and Sustainability Indicators, has now tracked that decline in unprecedented detail, combining 24 years of satellite imagery with machine learning to answer a deceptively simple question: what is really happening to the water that cities depend on? The answer is more troubling than a simple loss of area. The urban blue spaces of northern China are not only shrinking, they are fragmenting into smaller, more isolated pieces, a structural degradation that conventional monitoring has largely missed.</p>
<p>The research team, led by Weina Zhen and Donghui Shi, focused on the BTH urban agglomeration, a sprawling region of roughly 218,000 square kilometers that encompasses the megacities of Beijing and Tianjin along with eleven prefecture-level cities in Hebei Province. The region is an ideal natural laboratory for studying urban water dynamics. It holds only about 0.84 percent of China&#8217;s total water resources despite its enormous population, with per-capita water availability of roughly 243 cubic meters per year. Annual precipitation ranges from about 370 to 730 millimeters, nearly 70 percent of which falls in summer, and drought ranks among the region&#8217;s most damaging natural hazards. At the same time, decades of intensive urbanization, massive inter-basin water transfers and ambitious ecological restoration programs have reshaped the hydrological landscape in ways that vary dramatically from city to city.</p>
<p>To map these changes, the researchers drew on the China Land Cover Dataset, a 30-meter-resolution land cover product built from 335,709 Landsat images processed on the Google Earth Engine platform. For every year from 2000 to 2023, they extracted and merged the water and wetland classes to define urban blue space. While the underlying dataset achieves an overall classification accuracy of 79.31 percent nationally, the team conducted their own regional validation for 2000, 2010 and 2020 using stratified random sampling and manual visual interpretation against high-resolution historical imagery from Google Earth. The resulting average overall accuracy of 94.33 percent gave them confidence that the observed trends reflect real landscape change rather than classification noise.</p>
<p>The headline finding is stark. Blue-space area across the BTH region declined at a statistically significant average rate of about 16.82 square kilometers per year, falling from 3,182.61 square kilometers in 2000 to a peak of 3,299.93 square kilometers in 2004 before sliding to 2,909.11 square kilometers by 2010 and then fluctuating between roughly 2,900 and 3,000 square kilometers through 2023. A Pettitt change-point test identified 2009 as a statistically significant structural breakpoint, with mean blue-space area dropping from 3,199.26 square kilometers in the 2000–2009 period to 2,941.21 square kilometers from 2010 onward. The timing coincides with a period of rapid land conversion and severe hydroclimatic stress, including the 2008–2009 drought that gripped northern China, while the subsequent stabilization aligns plausibly with strengthened water-resource management, ecological restoration and large-scale water-transfer programs, though the authors are careful to note these correspondences do not establish causation.</p>
<p>Beneath the regional average, however, lies a patchwork of divergent local stories. Nine of the thirteen cities recorded statistically significant increases in blue-space area, led by Baoding, which gained an average of 3.60 square kilometers per year, expanding from 101.95 square kilometers in 2000 to 156.89 square kilometers in 2023. Shijiazhuang, Qinhuangdao, Handan, Xingtai, Chengde and Langfang also expanded significantly. In sharp contrast, Tianjin lost the most water surface, shrinking from 1,246.01 square kilometers in 2000 to 905.38 square kilometers in 2023, a cumulative loss of 340.62 square kilometers, while Tangshan lost 169.49 square kilometers. Zhangjiakou and Hengshui showed no statistically significant monotonic trend. Any assessment based on regional averages alone would have buried these dramatic intra-regional differences.</p>
<p>The study&#8217;s most innovative contribution lies in its treatment of landscape configuration as a distinct dimension of blue-space health. Rather than relying on area alone, the researchers computed ten landscape metrics capturing quantity, patch size distribution, fragmentation, shape complexity and connectivity, including the number of patches, patch density, the largest patch index, the landscape shape index, the perimeter-area fractal dimension, patch cohesion, effective mesh size, the splitting index and the aggregation index. These were synthesized into a single Composite Landscape Index, or CI, using an entropy-weighted TOPSIS method that objectively weights each indicator and ranks observations by their distance from ideal values. Pooling 312 city-year observations ensured the index remained spatially and temporally comparable across the entire study period.</p>
<p>The CI results reveal a systemic quality decline that mirrors, and in some cases contradicts, the area story. Regionally, the CI fell significantly, sharing the same 2009 breakpoint as the area series. Fragmentation metrics rose: more patches, higher patch density, greater subdivision and increasingly irregular patch shapes, while aggregation, cohesion and effective mesh size all declined, signaling weakened connectivity that hinders the movement of material, energy and organisms between water bodies. At the city level, the picture fractured further. Six cities, including Beijing, Shijiazhuang, Baoding, Cangzhou, Qinhuangdao and Langfang, showed significant CI increases, with Cangzhou improving fastest. Five cities, including Tianjin, Tangshan, Zhangjiakou, Chengde and Hengshui, declined significantly. Beijing achieved a structure-led improvement, with stable area but rising CI, while Chengde showed the opposite pattern, gaining water surface that was evidently more dispersed, artificial or seasonal, producing higher fragmentation and lower connectivity. Tianjin and Tangshan suffered simultaneous declines in both extent and configuration, marking them as priority targets for management intervention.</p>
<p>To identify what drives these changes, the team built separate XGBoost regression models for blue-space area and CI, interpreting them through SHAP (SHapley Additive exPlanations) values, a technique borrowed from cooperative game theory that quantifies each variable&#8217;s contribution to individual predictions. Eight candidate drivers passed multicollinearity screening: precipitation, temperature, the normalized difference vegetation index, fractional vegetation coverage, population, GDP, urbanization rate and environmental regulation intensity, the last proxied by the share of environment-related sentences in municipal government work reports. XGBoost outperformed Random Forest and Ridge regression baselines, achieving a test R-squared of 0.8984 for area and 0.8740 for CI, and feature-importance rankings proved robust across model architectures.</p>
<p>The SHAP analysis delivered a striking result: population, fractional vegetation coverage, NDVI and urbanization rate together accounted for 83.8 percent of the explanatory importance in the area model and 86.8 percent in the CI model, dwarfing the contributions of climate and policy variables. Population ranked first for area at 28.0 percent, with higher-population cities generally coinciding with larger blue spaces, while vegetation metrics dominated the CI model, with FVC contributing 27.9 percent. Notably, higher vegetation cover showed predominantly negative associations with both variables, which the authors interpret cautiously as a possible spatial competition between blue and green spaces under constrained land availability, or a reflection of vegetation-dominated landscapes where water patches remain small and fragmented. These are statistical associations conditional on city scale and geographic context, not evidence that urbanization benefits water or that vegetation harms it. Climate variables and environmental regulation each contributed roughly 10 percent or less, suggesting that within this dataset, human activity and surface ecological status, rather than macro-climate or governance signals, carry most of the explanatory weight.</p>
<p>The broader implications reach well beyond northern China. The findings align with documented blue-space losses in Delhi, Kolkata and Khulna, yet also echo evidence from the United States and elsewhere that urban water change is not a universal consequence of urbanization but depends on hydroclimatic background, development pressure, water engineering and management choices. The study&#8217;s central methodological message is that area and configuration must be assessed as separate dimensions; a city can gain water while losing connectivity, or hold its area constant while its landscape structure quietly improves or collapses. The authors acknowledge limitations, including mixed-pixel effects at 30-meter resolution, the smoothing inherent in city-level aggregation, and the crude proxy used for environmental regulation, and they call for finer spatial units and richer institutional data in future work. For planners in rapidly urbanizing regions worldwide, however, the lesson is already clear: protecting urban water means protecting not just how much there is, but how it is arranged.</p>
<p><strong>Subject of Research:</strong> Long-term remote sensing analysis of urban blue space extent, landscape configuration and their drivers in the Beijing–Tianjin–Hebei region</p>
<p><strong>Article Title:</strong> Quantifying the spatiotemporal dynamics and drivers of urban blue spaces in the Beijing–Tianjin–Hebei region using remote sensing</p>
<p><strong>Article References:</strong> Quantifying the spatiotemporal dynamics and drivers of urban blue spaces in the Beijing–Tianjin–Hebei region using remote sensing. (n.d.). <a href="https://doi.org/10.1016/j.indic.2026.101525" rel="noopener noreferrer">https://doi.org/10.1016/j.indic.2026.101525</a></p>
<p><strong>Image Credits:</strong> AI Generated</p>
<p><strong>DOI:</strong> <a href="https://doi.org/10.1016/j.indic.2026.101525" rel="noopener noreferrer">10.1016/j.indic.2026.101525</a></p>
<p><strong>Keywords:</strong> urban blue spaces, remote sensing, Beijing–Tianjin–Hebei, landscape fragmentation, XGBoost, SHAP, water resources, urbanization, land cover change, ecosystem connectivity, China, sustainable urban planning</p>
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		<title>How Attack Simulations on a River Basin&#8217;s Ecological Network Could Redesign Watershed Conservation</title>
		<link>https://scienmag.com/how-attack-simulations-on-a-river-basins-ecological-network-could-redesign-watershed-conservation/</link>
		
		<dc:creator><![CDATA[Violet Maxwell]]></dc:creator>
		<pubDate>Fri, 25 Sep 2026 21:25:38 +0000</pubDate>
				<category><![CDATA[Earth Science]]></category>
		<category><![CDATA[complex network theory]]></category>
		<category><![CDATA[conservation planning]]></category>
		<category><![CDATA[conservation planning for fragmented ecosystems]]></category>
		<category><![CDATA[ecological corridor optimization]]></category>
		<category><![CDATA[ecological corridors]]></category>
		<category><![CDATA[ecological network modeling]]></category>
		<category><![CDATA[ecological network resilience]]></category>
		<category><![CDATA[ecological networks]]></category>
		<category><![CDATA[ecological resilience testing]]></category>
		<category><![CDATA[environmental monitoring in river basins]]></category>
		<category><![CDATA[habitat connectivity]]></category>
		<category><![CDATA[habitat connectivity assessment]]></category>
		<category><![CDATA[landscape fragmentation]]></category>
		<category><![CDATA[landscape fragmentation analysis]]></category>
		<category><![CDATA[landscape optimization]]></category>
		<category><![CDATA[node removal simulation]]></category>
		<category><![CDATA[Qiantang River Basin]]></category>
		<category><![CDATA[resilience]]></category>
		<category><![CDATA[river basin habitat fragmentation]]></category>
		<category><![CDATA[stepping stones]]></category>
		<category><![CDATA[urban expansion impact on ecosystems]]></category>
		<category><![CDATA[watershed conservation strategies]]></category>
		<category><![CDATA[watershed landscape planning]]></category>
		<category><![CDATA[watershed management]]></category>
		<guid isPermaLink="false">https://scienmag.com/?p=214626</guid>

					<description><![CDATA[A new study of China's Qiantang River Basin combines static indicators with complex-network attack simulations to test, optimize, and validate the resilience of watershed ecological networks.]]></description>
										<content:encoded><![CDATA[<p>When a river basin loses habitat patches to sprawling cities, the damage is rarely visible in a single snapshot. Ecologists have long mapped ecological networks—the webs of core habitat areas, corridors, and stepping stones that let species move, disperse, and adapt across fragmented landscapes—but the tools used to judge whether those networks are truly resilient have remained stubbornly static. A new study of the Qiantang River Basin in eastern China argues that this one-dimensional view is not just incomplete but potentially misleading, and it proposes a full cycle of identification, assessment, optimization, and validation that could reshape how watershed landscapes are planned and protected.</p>
<p>The research, published in Environmental Monitoring and Assessment by Liwei Pang, Keyi Xu, and Wenbin Nie of Zhejiang A&amp;F University, tackles a problem that has grown acute as urban expansion slices once-contiguous ecosystems into isolated fragments. Ecological networks are meant to coordinate ecosystems across administrative boundaries, linking protected cores through corridors that channel the movement of organisms, water, nutrients, and even genetic material. Yet most resilience assessments to date have relied on static, one-dimensional indicators—a measure of connectivity here, a patch-size index there—without ever testing whether the network on the map would actually hold together under stress. Crucially, few studies have gone back after proposing an optimization to check whether the redesigned network is genuinely tougher than the original.</p>
<p>The team&#8217;s framework begins with the standard machinery of landscape ecology: identifying ecological sources as the network&#8217;s nodes, tracing corridors between them, and characterizing the resulting web with both structural and functional indicators. Structural measures capture the topology of the network—how nodes are connected, how redundant the pathways are, how centralized or dispersed the architecture is. Functional indicators reflect what the landscape actually permits, drawing on approaches such as least-cost modelling, which estimates the resistance a species encounters as it moves across different land covers. Together, these indicators define what the researchers call static resilience: the inherent structural and functional condition of the network at a given point in time, a baseline snapshot of ecosystem health.</p>
<p>But static snapshots, the authors contend, miss the defining property of resilience itself. Since C. S. Holling&#8217;s foundational 1973 work, resilience has meant the capacity of a system to absorb disturbance without collapsing—a property that only reveals itself when the system is actually perturbed. To capture this, the study borrows a technique from the physics of complex networks: progressive node removal. By simulating the loss of ecological sources one by one, either at random or in targeted fashion, the researchers track how overall network performance degrades until the system collapses. The proportion of nodes the network can lose before breakdown marks its collapse threshold, a dynamic measure of robustness that no single static index can provide. The approach echoes the landmark 2000 analysis by Albert, Jeong, and Barabási on the error and attack tolerance of complex networks, which showed that scale-free networks tolerate random failures remarkably well yet shatter when their hubs are deliberately removed.</p>
<p>Applying this dual framework to the Qiantang River Basin across two decades of land-cover data produced a result that is as counterintuitive as it is important. Static resilience declined continuously from 2000 to 2020, tracking the familiar story of fragmentation and degradation as urban footprints expanded through the basin. Yet the collapse threshold under random attacks—the fraction of ecological sources the network could lose before falling apart—actually rose from 20 to 26 percent over the same period. In other words, the network&#8217;s baseline condition worsened even as its tolerance for stochastic, unpredictable node loss improved. Deterioration and robustness, the study shows, can coexist. A network may become sparser and less functional while its remaining nodes happen to be arranged in a configuration that cushions it against random shocks.</p>
<p>This divergence is precisely why the authors argue that static and dynamic assessments are complementary rather than interchangeable. A planner relying solely on static indicators in 2020 might have concluded the basin&#8217;s network was uniformly failing and prioritized wholesale restoration. A planner relying solely on random-attack simulations might have seen improving robustness and relaxed. Only by reading both signals together does the true picture emerge: a network whose inherent condition is eroding but whose topology still offers some slack against unpredictable losses—slack that could be squandered if the wrong nodes disappear. That is where targeted attacks enter the analysis, deliberately removing the most critical ecological sources to expose which patches and corridors the network cannot afford to lose. These simulations identified key sources that play outsized roles in maintaining overall resilience, effectively handing planners a ranked list of the basin&#8217;s most consequential habitats.</p>
<p>With the diagnosis complete, the study moves to the optimization and validation stages that most previous work has omitted. The researchers strengthened the network by adding ecological stepping stones—small habitat patches that bridge long gaps between larger sources, a strategy whose importance for long-distance dispersal and range expansion was highlighted in a 2014 Journal of Applied Ecology analysis by Saura, Bodin, and Fortin. They also established differentiated buffer zones, tailoring protective management to the varying pressures and sensitivities of different parts of the landscape rather than applying a uniform rule. When the optimized network was put back through the same battery of static and dynamic tests, the reassessment showed measurably improved resilience, providing the empirical validation that the framework demands and that conservation planning so often lacks.</p>
<p>The significance of this closed loop—identify, assess, optimize, validate—extends well beyond one Chinese river basin. Watersheds are natural laboratories for network thinking because water itself imposes connectivity: rivers, riparian zones, and wetlands form linear corridors that urban development interrupts at its peril, degrading flood regulation, water purification, and habitat continuity simultaneously. Recent work on the Shiyang River Basin in arid northwest China, the Baiyangdian Basin, and the Wuhan metropolitan area has applied complex network theory to ecological systems with growing sophistication, and multi-scenario studies under combined climate and socioeconomic pathways are pushing the field toward forward-looking planning. The Qiantang study&#8217;s contribution is methodological discipline: it insists that any proposed redesign of a landscape must be stress-tested before it is adopted, much as engineers load-test a bridge before opening it to traffic.</p>
<p>For practitioners, the practical implications are concrete. Differentiated buffer zones mean that conservation effort can be allocated where attack simulations show vulnerability, rather than spread thinly and uniformly. Stepping stones offer a relatively low-cost intervention in landscapes where acquiring large new core habitats is politically or financially impossible, and their placement can be optimized specifically to raise collapse thresholds under both random and targeted disturbance. The identification of critical sources gives administrators a defensible priority ordering when development pressure forces trade-offs, and because the framework operates across administrative scales, it offers a common analytical language for municipalities that share a watershed but not a budget or a boundary. The research was supported by the National Natural Science Foundation of China under grant number 32501738.</p>
<p>There are, of course, limits to what node-removal simulations can capture. Real landscapes face disturbances—floods, fires, disease, land-use conversion—that rarely remove habitat patches in tidy sequences, and the functional performance of a network depends on the dispersal abilities of particular species, which generic resistance surfaces only approximate. The authors&#8217; data are drawn from the published paper and its supplementary materials, and the framework&#8217;s transferability to basins with different geomorphologies and land-tenure systems remains to be demonstrated. But the core insight stands on its own: resilience is not a number you read off a map, it is a behavior you observe under stress. By pairing the static health of a watershed&#8217;s ecological skeleton with its dynamic response to losing pieces of that skeleton, the Qiantang River Basin study offers conservation planners something they have rarely had before—a way to know, in advance, whether the network they are building will bend without breaking.</p>
<p><strong>Subject of Research:</strong> Assessment and optimization of ecological network resilience in the Qiantang River Basin watershed using complex network attack simulations</p>
<p><strong>Article Title:</strong> Reconsidering the optimization of watershed landscape pattern based on the enhancement of ecological network resilience</p>
<p><strong>Article References:</strong> Pang, L., Xu, K., &amp; Nie, W. (2026). Reconsidering the optimization of watershed landscape pattern based on the enhancement of ecological network resilience. <em>Environmental Monitoring and Assessment, 198</em>(10), Article 1115. <a href="https://doi.org/10.1007/s10661-026-15936-4" rel="noopener noreferrer">https://doi.org/10.1007/s10661-026-15936-4</a></p>
<p><strong>Image Credits:</strong> AI Generated</p>
<p><strong>DOI:</strong> <a href="https://doi.org/10.1007/s10661-026-15936-4" rel="noopener noreferrer">10.1007/s10661-026-15936-4</a></p>
<p><strong>Keywords:</strong> ecological networks, watershed management, resilience, complex network theory, landscape fragmentation, Qiantang River Basin, stepping stones, node removal simulation, landscape optimization, habitat connectivity, ecological corridors, conservation planning</p>
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