Resilience of wetland vegetation to recurrent drought in the Inland Niger Delta of Mali from 1982 to 2014

Hiernaux, Pierre; Turner, Matthew D.; Eggen, M.; Marie, Jérôme; Haywood, Mark

doi:10.1007/s11273-021-09822-8

Cited by 5 publications

(3 citation statements)

References 40 publications

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“…The impact of rainfall on population change from year to year may seem less drastic in arboreal bird species than in species bound to floodplains (Table 3 and 4), but in the long run a drought year has a much larger impact on arboreal birds because trees may die. Floodplain vegetation recovers quickly from a drought when it is followed by a wet year, even after a series of (extremely) dry years (Hiernaux et al 2021), but it takes many more years before woody vegetation has recovered after a drought year causing mass mortality of trees. In Australian drylands, a drought can offset tree regeneration and growth for at least fifty, relatively wet, years (Fensham et al 2009).…”

Section: Discussionmentioning

confidence: 99%

The Fortunes of Migratory Birds from Eurasia: Being on a Tightrope in the Sahel

Zwarts¹,

Bijlsma²,

Kamp³

2023

Ardea

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Many studies have shown that rainfall in the Sahel has a great influence on population trends of European bird species that spend the northern winter there. African bird species living in the Sahel, notably those that forage on the ground, have also shown significant declines, but independent of rainfall. This paper summarises the results of field data gathered in the entire Sahel and evaluates the many factors that play a role in the fortunes of birds. (1) Rainfall determines the extent of open water in the Sahel, and by default the fortunes of waterbirds. In recent decades the surface area of open water has increased because water tables have risen. (2) Rainfall south of the Sahel determines river discharge and therefore the surface of floodplains in the Sahel. Rainfall has a cumulative effect: discharges disproportionally decrease after a number of years with little rain, and vice versa. During the dry season (October-May), floodplains gradually dry out. In wet years, water -and hence food -is available for birds up to their departure, but in dry years birds become concentrated at the few remaining pools and so present an easy target for bird-trappers. Further desiccation leads to starvation. (3) After a year with heavy rainfall, seed is available in abundance, but a dry year results in a shift in the plant community and a low seed supply. Mortality among seedeaters increases under dry conditions. (4) In dry years, trees lose their leaves early on, forcing arboreal birds into a diminishing number of trees that retain leaves. In extremely dry years trees die on a massive scale and it takes many years before tree coverage is restored. When droughts occur in quick succession, as in 1972/73 and again in 1984/85, tree recovery is slow and populations of arboreal birds will continue to decline, or recover slowly or only partly (as for Eurasian Wryneck Jynx torquilla and Common Redstart Phoenicurus phoenicurus, whose numbers remain reduced by tenfold when compared to the 1950s, despite a slight recovery). Rainfall in the Sahel gradually recovered after 1990, as did the woody vegetation albeit with a delay, and many migratory bird species responded accordingly. Subalpine Warblers Curruca subalpina and Western Orphean Warblers Curruca hortensis have increased as much as threefold to fivefold since 1990. Southern European bird species, wintering in the arid parts of southern Sahara and Sahel, were hit the hardest during the Great Drought in 1969-1992, but also recovered the fastest, particularly strongly once rainfall had significantly recovered.Despite clear links between migratory birds and rainfall-related variables in their wintering areas, a migrant's world is more complicated than exclusively being constrained by rainfall. In the past century, the human population in sub-Saharan Africa has increased tenfold, with far-reaching consequences. (1) Cattle numbers boomed and grazing pressure increased greatly. Heavy grazing means lower grass seed production, especially of seeds that birds prefer. The steep decline of gr...

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Section: Discussionmentioning

confidence: 99%

The Fortunes of Migratory Birds from Eurasia: Being on a Tightrope in the Sahel

Zwarts¹,

Bijlsma²,

Kamp³

2023

Ardea

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“…Among inland wetlands, permanent freshwater marshes (10.5%), seasonal freshwater marshes (8.5%), permanent freshwater rivers (8%), and lakes (7%) were studied the most. Conversely, many inland wetland types, such as tundra wetlands, inland deltas, and freshwater springs, were rarely studied (<1%) [33][34][35]. Among human-made wetlands, aquaculture ponds (5%), irrigated land (3.5%), ponds (3%), and salt pans (2.5%) were studied the most, while seasonally flooded agricultural land, which includes pastures, was rarely studied (e.g., [36]).…”

Section: Wetland Typesmentioning

confidence: 99%

Long-Term Wetland Monitoring Using the Landsat Archive: A Review

et al. 2023

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Wetlands, which provide multiple functions and ecosystem services, have decreased and been degraded worldwide for several decades due to human activities and climate change. Managers and scientists need tools to characterize and monitor wetland areas, structure, and functions in the long term and at regional and global scales and assess the effects of planning policies on their conservation status. The Landsat earth observation program has collected satellite images since 1972, which makes it the longest global earth observation record with respect to remote sensing. In this review, we describe how Landsat data have been used for long-term (≥20 years) wetland monitoring. A total of 351 articles were analyzed based on 5 topics and 22 attributes that address long-term wetland monitoring and Landsat data analysis issues. Results showed that (1) the open access Landsat archive successfully highlights changes in wetland areas, structure, and functions worldwide; (2) recent progress in artificial intelligence (AI) and machine learning opens new prospects for analyzing the Landsat archive; (3) most unexplored wetlands can be investigated using the Landsat archive; (4) new cloud-computing tools enable dense Landsat times-series to be processed over large areas. We recommend that future studies focus on changes in wetland functions using AI methods along with cloud computing. This review did not include reports and articles that do not mention the use of Landsat imagery.

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“…To process these data effectively and accurately, a variety of algorithms for processing satellite images have been developed in remote sensing domain. A general approach of using multi-temporal satellite images for environmental monitoring is based on their pairwise comparison aimed at evaluating changes in land cover patterns (Hiernaux et al, 2021;Ogilvie et al, 2015). Time series analysis of Earth observation data has proven to be effective in the evaluation of landscape changes using several images covering the same area in various consecutive years.…”

Section: Introductionmentioning

confidence: 99%

Time Series Analysis of Landsat Images for Monitoring Flooded Areas in the Inner Niger Delta, Mali

Lemenkova,

Debeir

2023

Artificial Satellites

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This paper presents an R-based approach to mapping dynamics of the flooded areas in the Inner Niger Delta (IND), Mali, using time series analysis of Landsat 8–9 satellite images. As the largest inland wetland in West Africa, the habitats of IND offers high potential for biodiversity of the flood-dependent eco systems. IND is one of the most productive areas in West Africa. Mapping flooded areas based on satellite images enables to provide strategies for land management and rice planting and modelling vegetation types of IND. Our approach is based on using libraries of R programming language for processing six Landsat images, and each image was taken on November from 2013 to 2022. By capturing spatial and temporal structures of the satellite images on 2013, 2015, 2018, 2020, 2021 and 2022, the remote sensing data are combined to yield estimates of landscape dynamics that is temporally coherent, while helping to analyse fluctuations of spatial extent in fluvial wetlands caused by the hydrological processes of seasonal flooding. Further, by allowing packages of R to support image processing, an approach to mapping vegetation by NDVI, SAVI and EVI indices and visualising changes in distribution of different land cover classes over time is realised. In this context, processing Earth observation data by advanced scripting tools of R language provides new insights into complex interlace of climate-hydrological processes and vegetation responses. Our study contributes to the sustainable management of natural resources and improving knowledge on the functioning of IND ecosystems in Mali, West Africa.

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Resilience of wetland vegetation to recurrent drought in the Inland Niger Delta of Mali from 1982 to 2014

Cited by 5 publications

References 40 publications

The Fortunes of Migratory Birds from Eurasia: Being on a Tightrope in the Sahel

The Fortunes of Migratory Birds from Eurasia: Being on a Tightrope in the Sahel

Long-Term Wetland Monitoring Using the Landsat Archive: A Review

Time Series Analysis of Landsat Images for Monitoring Flooded Areas in the Inner Niger Delta, Mali

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