The Okavango Delta’s waterbirds – Trends and threatening processes

Francis, Roxane; Bino, Gilad; Inman, Victoria L.; Brandis, Kate J.

doi:10.1016/j.gecco.2021.e01763

Cited by 5 publications

(4 citation statements)

References 94 publications

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“…Our findings not only agree with those of other studies, in that they demonstrated trait-based wetland-adapted avifaunal responses to varying water levels in flood-prone ecosystems (Almeida et al, 2017(Almeida et al, , 2018Cumming et al, 2012;Francis et al, 2021;Lorenz on et al, 2017), but we also presented evidence of these responses based on landscape-wide dynamics. The longevity of dryland wetlands is reliant on continuous and periodic inundation in areas with low rainfall (Tooth & McCarthy, 2007).…”

Section: Significance Of Trait-based Responses To Changes In Inundati...supporting

confidence: 93%

“…Based on the consistency of these filtered values, we set our time frame of effect to 5 months prior to each survey up to the date of the survey for all explanatory variables (Figure 2). This period captures the most substantial changes in inundation area, as well as potential responses from wetland bird communities to these changes (Francis et al, 2021). For inundation area (in square kilometers), we used grid‐cell‐based mean values for the survey period and five 1‐month intervals predating this period.…”

Section: Methodsmentioning

confidence: 99%

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Landscape‐wide pulse events predict trait‐based responses among wetland birds in perennial channels of a dryland wetland

Becker,

Boyes,

Wittmer

et al. 2023

Ecological Applications

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Wetlands in arid or semi‐arid zones are vital for maintaining biodiversity but face growing threats. Flooding regime variability is a key driver of ecological dynamism in these systems, dictating primary productivity on a large spatial scale. Functional composition or diversity of wetland‐dependent bird species has been found to be sensitive to fluctuations in hydrological regimes and can thus be indicative of cascading ecosystem responses associated with climate change. In this paper we investigate whether large‐scale changes in inundation and fire – a significant additional biodiversity determinant in (semi‐)arid landscapes – were reliable predictors of functional group responses of wetland‐dependent birds along a perennial channel of the Okavango Delta, Botswana. We fit generalized additive models (GAM) to six years of bird survey data collected along ~190‐km‐long annual transects and use remotely sensed landscape‐level inundation estimates, as well as spatio‐temporal distance to fire, to predict responsiveness of seven trait‐based functional group abundances. During the surveys a total of 89 different wetland‐dependent bird species were recorded, including 76 residents, across all years, with below‐surface feeding waders consistently the most abundant functional group. Including estimated spatio‐temporal variability in flooding and fire, as well as their interactions, improved model fit for all seven functional groups, explaining between 46.8% and 68.3% of variability in functional group abundances. Covariates representing longer‐term variability in inundation generally performed better than shorter‐term ones. For example, variability in inundation over the 5 months preceding a survey best predicted the responses of all functional groups, which also all exhibited responsiveness to the interaction between flooding and fire. We were able to interpret the responses of individual functional groups, based on the resource exploitation assumption. Overall, our results suggest that perennial waters in dryland wetlands offer functional refugia to wetland‐dependent birds and highlight the indicative power of large‐scale trait‐based bird monitoring. Our findings demonstrate the potential utility of such a monitoring regime for dryland wetland ecosystems vulnerable to industrial‐scale anthropogenic pressure and associated climate change.ABSTRACT (Setswana)Morethetho wa go tshela ga metsi a makgobokgobo a a fitlhelwang mo nageng tsa komelelo, o rotloetsa mekgwa e dinonyane tse di fitlhelwang mo meeleng e e sa kgaleng ya makgobokgobo, di tsibogelang diemo ka teng.Makgobokgobo a a fitlhelwang mo dikgaolong tsa komelelo a botlhokwa mo go tshegetseng mefutafuta ya ditshidi, mme a lebaganywe ke matshosetsi. Go farologana ga ka fa metsi a makgobokgobo a tshelang ka teng, ke ntlha ya konokono e e tlhotlheletsang diphetogo mo nageng tse, ebile e laola ka fa dimela di dirang ka teng mo nageng eo ka bophara. Mefutafuta ya dinonyane tse di ikaegileng ka makgobokgobo e fitlhetswe e amiwa thata ke diemo tsa metsi tse di fetogafetogang, ka jalo mefuta e, e ka nna kaedi ya mekgwa e botshelo bo fetogang ka teng, segolobogolo fa re lebile phetogo e e sa tlwaelesegang ya loapi (Climate change). Mo mokwalong o, re sekaseka gore a diphetogo tsa maphashaphasha a metsi le melelo ya naga‐ nngwe ya dintlha tsa botlhokwa tse di rotloetsang mefutafuta ya ditshidi mo dinageng tsa komelelo ‐ ele bokao jo bo netlameng go ka supa ka fa mefuta ya dinoyane tse di ikaegileng ka makgobokgobo di tsibogelang diemo ka teng mo moeleng wa makgobokgobo a Okavango, mo Botswana. Go re thusa ka ditshekatsheko tse, re dirisitse boranyane jwa ditlhaka (Generalized Additive Models) go rarabolola patlisitso e e dirilweng mo dingwageng tse thataro ka dinonyane tse di bonweng mo tseleng ya sekgele sa boleele ja 190 km. Tsela e ya tshekatsheko e ne e tsamaiwa gangwefela mo ngwageng. Re ne gape ra dirisa maranyane a lefaufau (Remote sensing) go akanyetsa bophara jwa maphashaphasha a Okavango le go meta sekgele le sebaka sa molelo wa naga. Metlhale e ya tshekatsheko, e ne ya dirisiwa go akanyetsa pele phetogo ya dipalo tsa mefuta e supa ya dinonyane tsa makgokgobobo. Dipatlisiso di supile fa mo dingwageng tse thataro go gatisitswe mefuta e e farologanyeng ya dinonyane tse di ikaegileng ka makgobokgobo di le masome a a ferang bobedi le borobabongwe (89), go akarediwa tsa sennela ruri di le masome a supa le borataro (76). Go supegile gape fa mofuta wa dinonyane tse di jang dijo ko tlase ga metsi e le tsone di palo ntsi. Tharabololo ya maranyane a dipalo (model fit) e kgonne go tlhalosa gore fa gare ga masome mane le borataro le ntlha tse robabobedi mo lekgolong (46.8%) le masome marataro le boferabobedi le ntlha tse tharo mo lekgolong (68.3%) ya diphetogo tse di bonweng tsa mefuta ya dinonyane e bakilwe ke diphetogo tse di farologanyeng tsa go tshela ga metsi a makgobokgobo le molelo wa naga le ka fa dintlha tse di amanang ka teng. Mabaka a a rotloetsang diphetogo tsa maphashaphasha a metsi ka lebaka lo leleele, ka kakaretso a supegile a dira botoka go supa tsibogo ya dinonyane gona le a lebaka le le khutshwane. Sekai, diphetogo tsa selekanyo sa maphashaphasha a metsi mo kgweding tse tlhano (5 months) pele ga dipatlisiso di akanyeditse‐pele botoka ka fa ditlhopha tsotlhe tsa dinoyana di tsibogelang diemo ka teng. E supile tsibogelo diemo ya dinonyane e e bakiwang ke kamano magareng ga go tshela ga metsi le melelo wa naga. Re ne ra kgona go tlhalosa ka fa ditlhopha tsa dinonyane ka bongwe ja tsone di tsibogelang diemo ka teng, re dirisa kakanyetsong ya mekgwa ya tiriso ya ditsa tlholego. Ka kakaretso, maduo a rona a kaya fa metsi a sennela ruri a a bonwang mo makgobokgobong a naga ya komelelo, a a fa dinonyane tse di ikaegileng ka makgobokgobo lefelo la botshabelo, gape a senotse nonofo ya ditshekatsheko tsa peoleitho tse di dirwang ka dinonyane ka lebaka le selekanyo se segolo ebile se tseneletse. Maduo a rona a supile botlhokwa jwa tiriso ya ditlhotlhomiso tsa mofuta o mo makgobokgobong a a bonwang mo nageng tsa komelelo ebile a le mo diphatseng tsa kgotlelesego go tswa mo ditlhabololong le tse di amanang le phetogo e e sa tlwaelesegang ya loapi.

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Section: Significance Of Trait-based Responses To Changes In Inundati...supporting

confidence: 93%

Section: Methodsmentioning

confidence: 99%

Landscape‐wide pulse events predict trait‐based responses among wetland birds in perennial channels of a dryland wetland

Becker,

Boyes,

Wittmer

et al. 2023

Ecological Applications

View full text Add to dashboard Cite

show abstract

“…My findings not only agree with other studies, in that they have demonstrated traitbased wetland-adapted avifaunal responses to varying water levels in flood-prone ecosystems (Cumming et al 2012;Almeida et al 2017;Lorenzón et al 2017;Almeida et al 2018;Lorenzón et al 2019;Francis et al 2021), but I have also presented evidence of these responses along the central hydrological axis to the inundated totality of the system. Dryland wetlands' longevity is reliant on continuous and periodic inundation in areas with low rainfall (Tooth & McCarthy 2007).…”

Section: Significance Of Trait-based Responses To Changes In Inundati...supporting

confidence: 91%

“…Based on the consistency of these filtered values, I set the timeframe of effect to five months prior to each survey for all explanatory variables (Figure 8). This period captures the most substantial changes in inundation area, as well as potential responses from wetland bird communities to these changes (Francis et al 2021). For inundation area (km 2 ), I used section-based mean values for the survey period and five one-month intervals predating this period.…”

Section: Response Variablesmentioning

confidence: 99%

Of acoustics and avifauna: An integrative approach to avian ecology across the Southern Hemisphere

Becker¹

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Ecological monitoring is taking on greater significance as we try to better understand and mitigate anthropogenic impacts on Earth’s ecosystems and species. This has led to the development of more effective avenues of ecological inference and means to inform them. These include birds and their ecology, which often represent wider ecological processes reliably. Birds are also relatively easily observable, and not just visually. Vocalising taxa, like birds, are suitable subjects for acoustic monitoring. This compatibility has drawn increased focus to interdisciplinarity and integrated approaches to ecological research. In this thesis, I aimed to adopt an integrated approach to avian ecology in different ecosystems across the Southern Hemisphere, with an emphasis on (but not restricted to) acoustic monitoring. As an introductory study, I conducted a systematic review of bioacoustics literature from Africa, which, as a continent, is particularly well suited for acoustics-based biodiversity research. I reviewed 727 publications, dating back to 1953. My analyses revealed an overall exponential increase in bioacoustics research output, but notable underrepresentation of non-mammalian, non-terrestrial, conservation/human impact, and African-led studies. My results help illustrate the potential for expanding the field of bioacoustics on several levels across Africa. Following this, I used multi-year data (2013-2018) from bird surveys in a flood-pulsed dryland wetland in southern Africa to assess the responses of seven functional groups of wetland-dependent bird to varying (remotely sensed) inundation levels and fire frequencies. I used generalised additive modelling to help predict these responses, in an attempt to relate hydrological fluctuations to ecological processes along the central channel system of Botswana’s Okavango Delta. My models robustly predicted trait-based responses of wetland-dependent birds in the delta’s interior and showcase an avenue for long-term ecological monitoring in dryland wetland systems, to support management and mitigation efforts. Finally, I used data collected from passive acoustic monitoring (PAM) and camera trap surveys to investigate the determinants of functional, phylogenetic, and taxonomic structures of bird communities in urban forest patches across Wellington City in Aotearoa New Zealand. These determinants were broadly divided into (1) forest patch characteristics and (2) relative predator abundances. I identified older forest stands, distance to a sizable ecosanctuary, and cat, possum, and rat (Rattus spp.) abundances as key determinants of urban forest bird community structures. This study presents further evidence of how functional and phylogenetic community measures can be driven by different determinants compared to taxonomic metrics. I highlight the value of these findings in an urban conservation and ecological restoration context and evaluate the use of acoustically derived bird species richness appraisal tools in urban forest habitats. My thesis demonstrates how an integrated approach to avian ecology can help track ecological integrity and inform conservation strategies in a rapidly changing world.

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A review of the freshwater diversity in the Okavango Delta and Lake Ngami (Botswana): taxonomic composition, ecology, comparison with similar systems and conservation status

Moliner Cachazo,

Makati,

Chadwick

et al. 2023

Aquat Sci

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Freshwater organisms in the Okavango Delta and Lake Ngami (Botswana) provide direct and indirect benefits to people and the economy of the region. However, their existence could be potentially threatened by human activities (primarily, upstream water abstraction and planned hydropower structures) coupled with climate change. For their protection, it is essential to know their distribution, ecology, and status of the ecosystems that they inhabit. Publications that record taxa from the Delta at species level are scarce, particularly aquatic macroinvertebrates. Identifying organisms to species level can provide more accurate information for environmental monitoring and conservation programmes but requires significant training and expertise. Here, we present a comprehensive taxonomical review of 2204 freshwater species from the Okavango Delta and Lake Ngami, with additional 355 species found in other areas of Botswana that are likely to be present in the study region. We also compare the diversity of the Okavango Delta and Lake Ngami with two other tropical wetlands: the Pantanal (Brazil) and the Kakadu Region (Australia). We show that biodiversity in the Okavango Delta and Lake Ngami is higher than in previous estimates, with recorded species richness dominated by phytoplankton and macroinvertebrates. Most species are widespread across the system and southern Africa. The resulting database includes new records (Bryozoa, Porifera), information on species conservation status, habitat, ecology, distribution in continental Africa, site details and taxonomical notes. This will be an essential resource for researchers, conservation managers, policy makers and consultants investigating freshwater biodiversity in tropical wetlands in the region.

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The Okavango Delta’s waterbirds – Trends and threatening processes

Cited by 5 publications

References 94 publications

Landscape‐wide pulse events predict trait‐based responses among wetland birds in perennial channels of a dryland wetland

Landscape‐wide pulse events predict trait‐based responses among wetland birds in perennial channels of a dryland wetland

Of acoustics and avifauna: An integrative approach to avian ecology across the Southern Hemisphere

A review of the freshwater diversity in the Okavango Delta and Lake Ngami (Botswana): taxonomic composition, ecology, comparison with similar systems and conservation status

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