Animal diversity declines with broad-scale homogenization of canopy cover in African savannas

McCleery, Robert A.; Monadjem, Ara; Baiser, Benjamin; Fletcher, Robert J.; Vickers, Karen J.; Kruger, Laurence

doi:10.1016/j.biocon.2018.07.020

Cited by 61 publications

(64 citation statements)

References 77 publications

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“…So, the homogenization of vegetation structure, as seen in the case of increased woody encroachment in the absence of fire, affecting grassland/savanna specialists (Vieira and Marinho-Filho, 1998;Vieira, 1999;Henriques et al, 2000Henriques et al, , 2006Briani et al, 2004;Maravalhas and Vasconcelos, 2014;Abreu et al, 2017), will disrupt community structure resulting in biodiversity losses. Studies of open formations around the world also highlight the importance of habitat heterogeneity for maintaining biodiversity of the landscape (Andersen et al, 2012;Beale et al, 2018;McCleery et al, 2018;Bond, 2019;Costa et al, 2019). At our study area, open grasslands and savannas have particular importance for conservation at local and regional scales.…”

Section: Discussionmentioning

confidence: 84%

No Net Loss of Species Diversity After Prescribed Fires in the Brazilian Savanna

Durigan

Pilon

Abreu

et al. 2020

Front. For. Glob. Change

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Although savannas are fire-adapted ecosystems, prescribing fire for biodiversity conservation remains controversial at least in some regions where savannas occur. Faced with uncertainty, many decision makers and even scientists are still reluctant to prescribe fire for conservation purposes in fire-prone ecosystems, invoking the precautionary principle. Knowledge gaps on the ideal fire regime, such as how and when to burn, and especially the fear of biodiversity losses, are among the main arguments against fire management applied to remnants of native savanna vegetation. To inform this debate, we assessed the impact of prescribed fires on diversity of plants (different growth forms), ants, frogs, lizards, birds, and small mammals, in savannas and grasslands of the Brazilian Cerrado. We assessed the existing species richness, composition, and abundance in areas subjected to long periods of fire suppression and compared to that observed over a short period after prescribed dry-season fires, within each group of plants and animals. Whenever possible, we carried out separate analyses for grassland and savanna. Burning did not significantly reduce species richness of any of the groups analyzed, but had a positive effect on richness of graminoids in grassland. When analyzed at the species level, abundance of most animal groups did not show consistent responses to fire, except for a decrease in some frog populations in grasslands. Forbs, graminoids, and subshrubs increased in abundance after fire in grassland areas, though in savanna areas, abundance of forbs, and subshrubs tended to decline after fire. Species composition changed little in response to fire as indicated by low levels of dissimilarity between burned and unburned areas. These results confirm the high resilience of Cerrado biota to fire, as expected for savanna ecosystems in general. Besides, we demonstrate here that the risk of biodiversity losses cannot justify the objections to the use of prescribed fire for conservation purposes in the Cerrado.

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Section: Discussionmentioning

confidence: 84%

No Net Loss of Species Diversity After Prescribed Fires in the Brazilian Savanna

Durigan

Pilon

Abreu

et al. 2020

Front. For. Glob. Change

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“…Savanna ecosystems are characterized by the co-existence of grasses, forbs, and woody vegetation [2]. The percentage cover of these vegetation types shifts with environmental gradients and large herbivore diversity, density, and activity [3]. These landscapes are generally poorly suited to agricultural cultivation, and so the livelihoods of people living in savannas are often dependent on livestock, and therefore grazing resources [4].…”

Section: Introductionmentioning

confidence: 99%

Inter-Seasonal Time Series Imagery Enhances Classification Accuracy of Grazing Resource and Land Degradation Maps in a Savanna Ecosystem

et al. 2020

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In savannas, mapping grazing resources and indicators of land degradation is important for assessing ecosystem conditions and informing grazing and land management decisions. We investigated the effects of classifiers and used time series imagery—images acquired within and across seasons—on the accuracy of plant species maps. The study site was a grazed savanna in southern Kenya. We used Sentinel-2 multi-spectral imagery due to its high spatial (10–20 m) and temporal (five days) resolution with support vector machine (SVM) and random forest (RF) classifiers. The species mapped were important for grazing livestock and wildlife (three grass species), indicators of land degradation (one tree genus and one invasive shrub), and a fig tree species. The results show that increasing the number of images, including dry season imagery, results in improved classification accuracy regardless of the classifier (average increase in overall accuracy (OA) = 0.1632). SVM consistently outperformed RF, and the most accurate model and was SVM with a radial kernel using imagery from both wet and dry seasons (OA = 0.8217). Maps showed that seasonal grazing areas provide functionally different grazing opportunities and have different vegetation characteristics that are critical to a landscape’s ability to support large populations of both livestock and wildlife. This study highlights the potential of multi-spectral satellite imagery for species-level mapping of savannas.

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“…Concern about how changes in canopy cover and heterogeneity, due to changes in fire or cutting regimes, might affect understory communities are geographically widespread [18]. For example, canopy management via coppicing, a woodland management technique historically used in Europe but less consistently used recently, has resulted in significant changes in canopy structure in many areas of Europe [19,20].…”

Section: Introductionmentioning

confidence: 99%

Changes in conservation value from grasslands to savannas to forests: How a temperate canopy cover gradient affects butterfly community composition

2020

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Temperate savannas and grasslands are globally threatened. In the Midwest United States of America (USA), for example, oak savannas persist today at a small percentage of recent historic coverage. Therefore, restoration of habitats of low and intermediate canopy cover is a landscape conservation priority that often emphasizes returning tree density to a savannalike target value. Understanding how animal species react to such changes in vegetation structure is important for assessing the value of these restoration plans. We examined how butterfly community attributes in northwest Indiana USA, including community composition, richness, and abundance responded to a grassland-to-forest gradient of canopy cover. Butterfly community composition under intermediate canopy cover differed significantly from community composition in the most open or closed-canopy habitats. Composition of the plant community in flower was a significant predictor of three assessed attributes of the butterfly community-composition, richness, and abundance. Phenology, expressed as dayof-the-year, was also a strong predictor of these butterfly community attributes. Few butterfly species were habitat specialists as adults although canopy cover was a more important predictor of adult community composition than of richness or abundance of butterflies. Therefore, adult butterfly community differences along the canopy cover gradient were less about butterfly communities filled with habitat specialists for different canopy-defined habitats and more about gradual changes in community composition along this gradient. Overall, butterfly community richness was predicted to peak at about 34% canopy cover, butterfly abundance at about 53% canopy cover, community conservation value at about 59% canopy cover, and a combination of desirable conservation attributes-high diversity, high abundance, and high conservation value-was predicted to reach a peak of co-occurrence at about 67% canopy cover suggesting that habitats of intermediate canopy cover might be particularly effective for butterfly conservation in this region.

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Animal diversity declines with broad-scale homogenization of canopy cover in African savannas

Cited by 61 publications

References 77 publications

No Net Loss of Species Diversity After Prescribed Fires in the Brazilian Savanna

No Net Loss of Species Diversity After Prescribed Fires in the Brazilian Savanna

Inter-Seasonal Time Series Imagery Enhances Classification Accuracy of Grazing Resource and Land Degradation Maps in a Savanna Ecosystem

Changes in conservation value from grasslands to savannas to forests: How a temperate canopy cover gradient affects butterfly community composition

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