Lian Feng

• PhD
• Professor (Full) at Southern University of Science and Technology

Algal blooms constitute an emerging threat to global inland water quality, yet their spatial and temporal distribution at the global scale remains largely unknown. Here we establish a global bloom database, using 2.91 million Landsat satellite images from 1982 to 2019 to characterize algal blooms in 248,243 freshwater lakes, representing 57.1% of t...

Lakes are important natural resources and carbon gas emitters and are undergoing rapid changes worldwide in response to climate change and human activities. A detailed global characterization of lakes and their long-term dynamics does not exist, which is however crucial for evaluating the associated impacts on water availability and carbon emission...

Phytoplankton blooms in coastal oceans can be beneficial to coastal fisheries production and ecosystem function, but can also cause major environmental problems1,2—yet detailed characterizations of bloom incidence and distribution are not available worldwide. Here we map daily marine coastal algal blooms between 2003 and 2020 using global satellite...

Widespread increases in lake surface water temperature have been documented in recent decades. Yet our understanding of global lake warming is mainly based on summertime measurements and includes relatively few observations from high latitudes (>60° N) where half of the world’s lakes are located. Here we provide temporally and spatially detailed hi...

Harmful algal blooms can produce toxins that pose threats to aquatic ecosystems and human health. In this Review, we outline the global trends in harmful algal bloom occurrence and explore the drivers, future trajectories and potential mitigation strategies. Globally, harmful algal bloom occurrence has risen since the 1980s, including a 44% increas...

Lake heatwaves (extreme hot water events) can substantially disrupt aquatic ecosystems. Although surface heatwaves are well studied, their vertical structures within lakes remain largely unexplored. Here we analyse the characteristics of subsurface lake heatwaves (extreme hot events occurring below the surface) using a spatiotemporal modelling fram...

Aquatic vegetation contributes to lake methane emissions, but changes in aquatic vegetation in northern (>40° N) lakes remain unknown, hindering evaluations of its importance in estimating lake emissions. Here we use Landsat imagery to monitor aquatic vegetation (mainly emergent and floating vegetation) in 2.7 million northern lakes from 1984 to 20...

Over the past 50 years, nutrient discharge into freshwater ecosystems has significantly increased due to intensive fertilizer application in China. This has led to frequent environmental issues associated with nutrient enrichment, such as algal blooms, in a number of individual lakes. However, the linkages between terrestrial nutrient sources and a...

We compile a unique satellite‐derived panel dataset to investigate the impacts of cropland coverage on the outbreak of Harmful Algal Blooms (HABs) in China between 2003 and 2019. Our results indicate that a 1% increase in cropland leads to a 0.5% increase in the size of HABs in lakes larger than 20 km². The increase in cropland not only affects the...

Aquatic vegetation (AV) is vital for maintaining the health of lake ecosystems, with submerged aquatic vegetation (SAV) and floating/emergent aquatic vegetation (FEAV) representing clear and shaded states, respectively. However, global SAV and FEAV dynamics are poorly understood due to data scarcity. To address this gap, we developed an innovative...

The recent increase in algal blooms in lakes, potentially exacerbated by climate warming, is of global concern. However, a spatially and temporally detailed characterization of algal bloom trends at a global scale has been lacking, posing challenges to definitively attribute warming as a primary driver. Here, we used daily MODIS satellite observati...

Improving agricultural sustainability is a global challenge, particularly for China's high-input and low-efficiency cropping systems with environmental tradeoffs. Although national strategies have been implemented to achieve Sustainable Development Goals in agriculture, the potential contributions of crop switching as a promising solution under var...

Fluvial sediment transport, a key pathway for global biogeochemical cycling, has changed markedly in the Anthropocene. However, disaggregating the compound effects of anthropogenic stresses on fluvial sediment transport at the global scale remains a challenge. Here we map the suspended sediment concentrations for global river channels, based on sat...

Inherent optical properties (IOPs) are crucial parameters for assessing water quality, with widely applied estimation methods established for open oceans. However, the estimation of IOPs for inland and coastal waters remains a longstanding challenge due to their complex optical properties. To address this, we developed a deep-learning assisted quas...

Human-transformed agricultural and aquacultural ponds, collectively referred to as “dike-pond systems”, play a crucial role in ensuring food security but also contribute to the widespread loss of natural wetlands. However, spatially and temporally explicit patterns of dike-pond systems have not been thoroughly documented globally. Here, we map the...

River ice plays a crucial role in hydrology, ecosystems, and socio-economic systems in mid-to-high latitude regions. However, there is a notable gap in the analysis of patterns and trends in river ice phenologies and their influence factors at the river level. In this study, we developed a practical method to identify river ice phenologies by lever...

Nutrients such as phosphorus and nitrogen lead to extensive growth of harmful algae in lakes and reservoirs, which results in eutrophication. The driving mechanism of primary productivity change in lakes and reservoirs at a wide spatial and temporal scale remains largely unknown. We establish a water quality database using a stacking machine learni...

Extreme within-lake conditions have the potential to exert detrimental effects on lakes. Here we use satellite observations to investigate how the occurrence of multiple types of extremes, notably algal blooms, lake heatwaves, and low lake levels, have varied in 2724 lakes since the 1980s. Our study, which focuses on bloom-affected lakes, suggests...

This chapter assesses surface water changes due to climate change and human activities, by particularly examining runoff and streamflow. Changes in the hydrological cycle due to climate change and human intervention can lead to diverse environmental impacts and risks. Fresh water is the agent that delivers many of the impacts of climate change on s...

River sediments play a critical role in sustaining deltaic wetlands. Therefore, concerns are raised about wetlands’ fate due to the decline of river sediment supply to many deltas. However, the dynamics and drivers of suspended sediment near deltaic coasts are not comprehensively assessed, and its response to river sediment supply changes remains u...

Since the launch of the Landsat missions, they have been widely employed for monitoring water environments. However, the designed revisiting period of Landsat satellites is 16 days, leading to large uncertainties when tracking long-term changes in water environmental parameters characterized by high spatiotemporal dynamics. Given this challenge, co...

Crop production is a large source of atmospheric ammonia (NH3), which poses risks to air quality, human health and ecosystems1–5. However, estimating global NH3 emissions from croplands is subject to uncertainties because of data limitations, thereby limiting the accurate identification of mitigation options and efficacy4,5. Here we develop a machi...

Sand is a vital ingredient for modern structures and to meet demand, a substantial volume of sand is extracted illegally from riverbeds globally. The Vietnamese Mekong Delta is one of the largest delta in Asia and it has a long history of riverbed sand mining. We quantified the illegal sand mining rate in this major sand mining hotspot, as the diff...

Correcting atmospheric effects over inland and coastal waters poses a significant challenge in ocean color applications due to the prevalence of strongly absorbing aerosols, often resulting in over-correction during atmospheric correction (AC) processes. To address this challenge, our previous study introduced novel global gridded aerosol models ta...

Rapid urbanization has dramatically increased the demand for river sand, leading to soaring sand extraction rates that often exceed natural replenishment in many rivers globally. However, our understanding of the geomorphic and social-ecological impacts arising from Sand Mining (SM) remains limited, primarily due to insufficient data on sand extrac...

Lakes in the Northeast Plains-Mountain Lake Region (NPLR) of China face severe risks of eutrophication due to climate change and intensive anthropogenic pressures. As a vital indicator for eutrophication status, the dynamics of chlorophyll-a (Chl-a) concentrations in NPLR lakes were, for the first time, comprehensively investigated in this study. A...

Phytoplankton, the foundation of marine ecosystems, are undergoing unprecedented changes under global warming, particularly in the Arctic Ocean. Yet the understanding of the long-term and seasonal evolutions in the Arctic phytoplankton is limited due to the lack of observations in the winter half year, including polar nights. Here, utilizing the sp...

Human displacement is one of the most pressing global issues, and China has the world's largest population affected by floods. Yet, the spatial and temporal variations of China’s Human Displacement Risk (HDR) caused by floods remain unclear. Here, we investigated China's HDR caused by extreme floods under different global warming levels, including...

Temporal monitoring of inland water bodies using remote sensing images is often impeded by missing data caused by clouds and other adverse conditions. To date, various data recovery algorithms have been developed based on the water occurrence threshold (WOT), where the contaminated pixels are recovered by using long-term historical water distributi...

Rapid urbanization has dramatically increased the demand for river sand, leading to soaring sand extraction rates that often exceed natural replenishment in many rivers globally. However, our understanding of the geomorphic and social-ecological impacts arising from Sand Mining (SM) remains limited, primarily due to insufficient data on sand extrac...

Many lakes in China suffer from algal bloom problems. However, the spatial and temporal distribution of lacustrine algal blooms at the national scale has not been well characterized. Here, we developed an automated algal bloom surface scums (hereafter referred to as algal bloom) detection algorithm for Moderate-Resolution Imaging Spectroradiometer...

The use of standard aerosol models for atmospheric correction over inland and nearshore coastal waters generates large uncertainties due to their inability to appropriately characterize aerosols in those regions. To address this problem, we developed new aerosol models using data acquired from 1,475 Aerosol Robotic Network (AERONET) sites distribut...

Thermal discharge from nuclear power plants poses a threat to the received natural water bodies, but the long-term extent and intensity of their surface thermal plumes remain unclear. In this study, we proposed a method to determine the background area for each drainage outlet and delineate the mixed surface thermal plumes based on 7,172 Landsat th...

Over the past half-century, drastically increased chemical fertilizers have entered agricultural ecosystems to promote crop production on the Yangtze Plain, potentially enhancing agricultural nutrient sources for eutrophication in freshwater ecosystems. However, long-term trends of nitrogen dynamics in terrestrial ecosystems and their impacts on eu...

Extensive and complex changes in spring vegetation phenology have occurred in the Pan‐Arctic over the last several decades. However, the role of snow cover at the start of the growing season (SOS) under different climatic conditions remains unclear. Therefore, we compare the effects of four snow indicators on SOS from 1982 to 2015 based on long‐ter...

Losses of coastal wetlands have been observed worldwide, but the extent to which inland wetlands have been exploited by humans is currently unknown on a global scale. Here, we map the distribution of land reclamation over global inland and coastal wetlands using high-resolution satellite observations. Results show that the total area of reclaimed w...

Renewable energy is the key to reduce greenhouse gas emissions, and is one of the most concerned issues worldwide. China has the largest hydropower potential in the world. Yet, how China’s hydropower potential will change under 1.5 oC and 2.0 oC global warming and beyond remains unknown. Here, we find that China’s hydropower will increase greatly b...

Over the past half century, drastically increased chemical fertilizer have entered agricultural ecosystems to promote the crop production on the Yangtze Plain, potentially enhancing agricultural nutrient sources for eutrophication in freshwater ecosystems. However, long-term trends of nitrogen dynamics in terrestrial ecosystems and their impacts on...

A robust and reliable chlorophyll-a (Chla) concentration algorithm is still lacking for optically complex waters due to the lack of understanding of the bio-optical process. Machine learning approaches, which excel at detecting potential complex nonlinear relationships, provide opportunities to estimate Chla accurately for optically complex waters....

Although the 5% mission goal for NASA’s standard atmospheric correction (AC) algorithm (i.e., the near-infrared (NIR) algorithm) for oligotrophic oceans has been met, this algorithm applies only to blue bands and is highly sensitive to contamination from cloud straylight and sunglint. Here, we developed an AC algorithm for clear waters based on dee...

Global river systems are experiencing rapid changes in sediment transport under growing anthropogenic and climatic stresses. However, the response of sediment discharge to the coupled influence of anthropogenic and natural factors and the associated impacts on the fluvial geomorphology in the Yangtze and Mekong rivers are not comprehensively assess...

Extensive human activities and climate change in recent decades have triggered severe eutrophication problems in the coastal oceans in the Greater Bay Area (GBA) of China. However, a comprehensive characterization of the spatial and temporal patterns of chlorophyll-a (Chl-a, a major indicator of phytoplankton biomass) in this region is not availabl...

The water environment has experienced prominent changes worldwide in recent decades, especially in inland waters. As an important lake region in China, the water turbidity of lakes/reservoirs in the Northeast Plain-Mountainous Region (NPLR) remains less understood, especially the influencing mechanisms of regional climatic conditions and human acti...

In recent decades, the reclamation of lakes has captured 42% of the total lake area of the Yangtze Plain in China and introduced additional pressure on lacustrine water quality. While lacustrine dissolved organic matter (DOM) is critical in regulating biogeochemical processing and aquatic biodiversity, the impact of reclamation on the molecular-lev...

Lake ice loss has been detected worldwide due to recent climate warming, yet spatially and temporally detailed information on the changes inglobal ice phenology does not exist. Here, we build a global lake ice phenologydatabase comprising three lake ice phenologies –freeze-up, break-up, and ice duration –for each year acrosstwocenturies (1900-2099)...

Glaciers and snow are natural water reservoirs in the Tibetan Plateau (TP), affecting ecosystems, water and food security, and more than one billion downstream people. Meltwater volumes are traditionally estimated using the degree‐day concept considering only air temperature, which cannot consider the influence from downward solar and longwave radi...

The river beds of the Mekong Delta are some of the most intensively sand mined places in the world. However, sand mining budgets remain limited to rough and indirect estimates. Here, we provide a first systematic, field-based estimation of the Mekong Delta’s sand mining budget. This budget overcomes the limitations of relying on officially declared...

Understanding concurrent drought events in global main croplands is crucially important for food security, effective adaptation to climate change and human well‐being. Yet, there is a lack of comprehensive studies on concurrent drought probability changes among main crop production countries on a global scale, especially for the future. Here, we st...

Flooding in the Yangtze River Basin could severely damage socio-economic development, river ecosystems, food security, hydropower production and transportation in China. The Yangtze River Basin accounts for approximately 30% of China’s gross domestic product (GDP) and is an engine for the country’s rapid economic growth. One commonly held belief is...

Over the past two decades, lakes in Yangtze Plain have suffered from serious eutrophication, in some regions with increased frequency of cyanobacteria blooms over years. In this study, we investigated the underlying causes of eutrophication using a combination of process-based ecosystem modelling and statistical data analysis. We found that terrest...

As an important agriculture production area in the world and a flood prone area, future hydro-climate changes in winter and spring in Northeast China could have remarkable influence on spring water resources and flood. Yet, studies on future hydro-climate variations with special considerations of snow influences remain limited so far in the region....

GLDAS2.0 provides long‐term fine resolution gridded hydrometeorological data sets, which are necessary for water‐related studies, particularly in some transboundary rivers that are partially without observation. Yet, GLDAS2.0 has only been validated at limited locations, and few studies have been conducted to develop approaches to correct the GLDAS...

Study region Northeast China Study focus Northeast China is one of the largest agricultural regions in the world and a strategically important granary for China. Information on hydrological extremes is crucially important for water management. Yet, comprehensive studies on hydrological extremes, both extreme flood and drought events, based on hydr...

Study region Northeast China Study focus Northeast China is an important region for industry and agriculture in China. In this region, investigations are lacking on the spatial distribution of snow melt contributions to the spring maximum runoff/discharge, and no studies have compared the spring and summer potential flood risks. Here, for the firs...

This study focuses on the evolution of flood risk in the Yangtze River Basin under climate change, which is a critical issue for socioeconomic development in future. In this study, we 1) compared the 1998 and 2020 floods and found that the destructiveness of a given discharge is now greater than before; 2) revealed three issues related to the above...

Widespread water losses in endorheic river basins have triggered ecological disasters. Agricultural irrigation has been one of the major drivers of water losses. It is imperative to address the water conflict between agriculture and ecosystems in arid regions, but significant gaps remain in knowledge of the water-agriculture-ecosystem nexus. The He...

More than 50% of global lakes periodically freeze, and their lake ice phenology is sensitive to climate change. However, spatially detailed quantification of the changes in lake ice at the global scale is not available. Here, we map ice cover in >33,000 lakes throughout the North Temperate Zone (23.5-66.5°N) using 0.55 million Landsat images from 1...

Synthetic aperture radar (SAR) has great potential for timely monitoring of flood information as it penetrates the clouds during flood events. Moreover, the proliferation of SAR satellites with high spatial and temporal resolution provides a tremendous opportunity to understand the flood risk and its quick response. However, traditional algorithms...

Submerged aquatic vegetation (SAV) is one of the main producers in inland lakes. Tracking the temporal and spatial changes in SAV is crucial for the identification of state changes in lacustrine ecosystems, such as changes in light, nutrients, and temperature. However, the available SAV classification algorithms based on remote sensing are highly d...

The river beds of the Mekong Delta are some of the most intensively sand mined places in the world, however sand mining budgets are limited to rough and indirect estimates. Here, we provide a systematic, semi-physically based estimation of the Mekong Delta’s sand mining budget. We provide a quantified budget that overcomes limitations resulting fro...

A practical Atmospheric Correction algorithm for inLand and Nearshore Coastal waters (ACLANC) is proposed in this study. The ACLANC algorithm uses interpolated aerosol optical depth (AOD) products (AOD $_{\mathrm {interp}}$ ) from nearby land surfaces and simulates the corresponding aerosol reflectance spectrum using a combination of the continent...

China’s largest desert freshwater lake, Hongjian Nur (HN), which is the largest habitat of relict gull (Larus relictus), has rapidly changed in recent years. However, it is difficult to quantitatively monitor the dynamics of the lake and determine the causes of its changes due to the lack of in situ observation. In this study, a remote sensing-base...

Water turbidity is an important indicator of water quality, which regulates primary production by changing the light field in the water column. Thus, monitoring the spatial and temporal variations in water turbidity is environmentally and biologically important. In this study, nine commonly used spectral index algorithms were tuned using in situ da...

The lakes on the Yangtze Plain, a critical source of freshwater and fisheries for hundreds of millions of people in China, have lost a considerable portion of their surface area due to reclamation since the 1950s. Landsat satellites can provide long-term collections of high-resolution images and thus offer great potential for hindcasting the lake r...

As essential parts of the unique ecosystem of Tibetan Plateau (TP), the sizes and associated physical properties of alpine lakes have long been investigated. However, little is known about one of the most critical biogeochemical properties, i.e. the Chlorophyll-a (Chl-a) concentrations. Here, for the first time, we presented a comprehensive investi...

Lakes are essential components of the water cycle and ecosystems. Therefore, the ecology and water security of lakes is of great concern. However, on the Tibetan Plateau (TP), which is known as the Asian water tower, knowledge of lake water quality is in its infancy. In this study, we developed a Moderate Resolution Imaging Spectroradiometer (MODIS...

With the longest archive of satellite remote sensing images, the Landsat series of satellites have demonstrated their great potential in aquatic environmental studies. However, although various atmospheric correction (AC) methods have been developed for Landsat observations in water color applications, a comprehensive assessment of their accuracies...

Understanding of turbidity, an indicator of water quality, is of great importance in cities and can have significant implications for human society. Many users are interested in mapping turbidity using remote sensing tools for long-term and large-scale monitoring. This study aims to derive turbidity maps in an urbanizing city and to identify the dr...

As one of the major agricultural regions in the world, water scarcity problems in Northeast China have drawn much attention recently. Because of cold and long winter period, snow is an important component in the hydrological system. Yet few studies have been conducted to systematically assess its role. This study quantified the effects of snow on r...

Over the past half century, the Yangtze Plain of China has experienced rapid economic development. Lake reclamation (i.e., conversion of natural lake/wetland areas to agricultural/urban land or aquaculture, thereby reducing the area of natural waters) in particular has greatly contributed to meeting the increasing demands for food and urban develop...

The directional-hemispherical reflectance and transmit-tance of needle-shaped leaves are redefined in this study. We suggest that the reflected and transmitted radiation of a leaf should be distinguished by the illuminated and shaded leaf surfaces rather than the usual separation of the two hemispheres by a plane perpendicular to the incoming radia...