Woody plant decline in the Sahel of western Niger (1996–2017):is it driven by climate or land use changes?

Hiernaux, Pierre; Kalilou, Amadou Adamou; Kergoat, Laurent; Brandt, Martin; Mougin, E.; Fitts, Yasmin

doi:10.1016/j.jaridenv.2022.104719

Cited by 4 publications

(3 citation statements)

References 51 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…More recent high resolution satellite images have instead been compared to aerial photographs, available since the 1940s, and satellite photos, available for the period 1965–1972, to show the decline of woody cover during the Great Drought (Tappan et al 2004, Brandt et al 2014, Spiekermann et al 2015, CILSS 2016, Zwarts et al 2018). Thanks to (very) high resolution satellite images available since 2002, the opportunities to quantify the gradual increase of the woody cover in the past few decades in relation to human population density, land use, soil and average rainfall are unprecedented (Brandt et al 2017 & 2018, Hiernaux et al 2022). Ground surveys have added much detail to satellite imagery, or indeed were the only sources of information at a time when satellites were just entering the scene.…”

Section: Discussionmentioning

confidence: 99%

“…The ongoing depletion of woody vegetation was caused by the expansion of the cropped area, a shortening of the crop-fallow cycle and increasing pressure on wood resources (fuel, construction material). During these two decades neither rainfall nor soil moisture had significantly changed (Hiernaux et al 2022). Outcomes of local and regional studies have a large decline of tree diversity in common (Table 6), which does not augur well for arboreal birds.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

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

Zwarts¹,

Bijlsma²,

Kamp³

2023

Ardea

View full text Add to dashboard Cite

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...

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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

Zwarts¹,

Bijlsma²,

Kamp³

2023

Ardea

View full text Add to dashboard Cite

show abstract

“…In the Dosso Reserve and surrounding areas, agriculture and grazing are the main productive activities to meet the increasing demands of population growth, which led to the widespread conversion of grassland, shrubs, and forests into cropland and pastures [14,18,25,64]. In addition, the Dosso Reserve is the main source of firewood supply and medicinal materials for the surrounding areas, and unsustainable wood extraction led to its degradation [65][66][67]. Overall, frequent land clearing for crop fields and pastures, overgrazing by livestock, and overexploitation of woody vegetation for fuel and medicinal materials reduced the fractional abundance of natural vegetation in a long-term period and resulted in vegetation browning.…”

Section: Drivers Of Vegetation Greenness Dynamicsmentioning

confidence: 99%

Hydrological Factor and Land Use/Land Cover Change Explain the Vegetation Browning in the Dosso Reserve, Niger

Zeng,

Jia,

Jiang

et al. 2024

Remote Sensing

View full text Add to dashboard Cite

The West Sahel is facing significant threats to its vegetation and wildlife due to the land degradation and habitat fragmentation. It is crucial to assess the regional vegetation greenness dynamics in order to comprehensively evaluate the effectiveness of protection in the natural reserves. This study analyzes the vegetation greenness trends and the driving factors in the Dosso Partial Faunal Reserve in Niger and nearby unprotected regions—one of the most important habitats for endemic African fauna—using satellite time series data from 2001 to 2020. An overall vegetation browning trend was observed throughout the entire region with significant spatial variability. Vegetation browning dominated in the Dosso Reserve with 17.7% of the area showing a significant trend, while the area with significant greening was 6.8%. In a comparison, the nearby unprotected regions to the north and the east were found to be dominated by vegetation browning and greening, respectively. These results suggest that the vegetation protection practice was not fully effective throughout the Dosso Reserve. The dominant drivers were also diagnosed using the Random Forest model-based method and the Partial Dependence Plot tool, showing that water availability (expressed as soil moisture) and land use/land cover change were the most critical factors affecting vegetation greenness in the study region. Specifically, soil moisture stress and specific land management practices associated with logging, grazing, and land clearing appeared to dominate vegetation browning in the Dosso Reserve. In contrast, the vegetation greening in the central Dosso Reserve and the nearby unprotected region to the east was probably caused by the increase in shrubland/forest, which was related to the effective implementation of protection. These findings improve our understanding of how regional vegetation greenness dynamics respond to environmental changes in the Dosso Reserve and also highlight the need for more effective conservation planning and implementation to ensure sustainable socio-ecological development in the West Sahel.

show abstract