Fish, Floods, and Ecosystem Engineers: Aquatic Conservation in the Okavango Delta, Botswana

Mosepele, Ketlhatlogile; Moyle, Peter B.; Merron, Glenn S.; Purkey, David; Mosepele, B.

doi:10.1525/bio.2009.59.1.9

Cited by 99 publications

(104 citation statements)

References 36 publications

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“…Herbivore density was a major predictor of d 13 C values of seston, FBOM, and periphyton in the Mara River during the dry and wet seasons, further highlighting the potentially important role played by large mammalian herbivores in the organic matter dynamics and energy sources for consumers in the river. The influence of hippos as vectors of terrestrial organic matter that fuel food webs in Africa's aquatic ecosystems is receiving increased attention (Gereta and Wolanski 1998;Grey and Harper 2002;Mosepele andothers 2009, Pennisi 2014). Inside and outside the MMNR, large populations of hippos (4143 individuals, Kanga and others 2011) graze on terrestrial savanna C4 grasses during the night and excrete partially digested excreta in the Mara River and its tributaries during the day.…”

Section: Discussionmentioning

confidence: 99%

Are Large Herbivores Vectors of Terrestrial Subsidies for Riverine Food Webs?

et al. 2015

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The tropical savannas of Africa have witnessed a dramatic reduction in native large mammalian herbivore populations. The consequences of these changes for terrestrial-aquatic food-web linkages are poorly documented. We used natural abundances of stable carbon and nitrogen isotopes (d 13 C, d 15 N) to determine spatial and temporal patterns in the importance of herbivore-mediated subsidies for consumers in the Mara River, Kenya. Potential primary producers (terrestrial C3 and C4 producers and periphyton) and consumers (invertebrates and fish) were collected during dry and wet seasons from different sites along the river, representing a gradient from forested highlands to natural savanna grasslands with high herbivore densities across mixed agricultural and livestock-dominated zones. Bayesian mixing models were used to estimate the relative contributions of terrestrial and algal sources of organic carbon supporting consumer trophic groups. Organic carbon sources differed for consumer groups and sites and with season. Overall, periphyton was the major energy source for most consumer groups during the dry season, but with wide 95% confidence intervals. During the wet season, the importance of terrestrial-derived carbon for consumers increased. The importance of C3 producers declined from 40 and 41% at the forested upper reaches to 20 and 8% at river reaches receiving hippo inputs during the dry and wet seasons, respectively. The reciprocal increase in the importance of C4 producers was higher than expected based on areal cover of riparian vegetation that was mainly C3. The importance of C4 producers notably increased from 18 and 10% at the forested upper reaches to 33 and 58% at river reaches receiving hippo inputs during the dry and wet seasons, respectively. This study highlights the importance of large herbivores to the functioning of riverine ecosystems and the potential implications of their loss from savanna landscapes that currently harbor remnant populations. Although the importance of C4 terrestrial carbon in most river systems has been reported to be negligible, this study shows that its importance can be mediated by large herbivores as vectors, which enhance energetic terrestrial-aquatic linkages in rivers in savanna landscapes.

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Section: Discussionmentioning

confidence: 99%

Are Large Herbivores Vectors of Terrestrial Subsidies for Riverine Food Webs?

et al. 2015

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“…However, floods are a vital part of many ecosystems (e.g. Benke 2001;Mosepele et al, 2009). For example, lateral connectivity between rivers and their floodplains during flood pulses is a key driving force for the river ecosystem (Junk et al 1989;Tockner et al, 2001) bringing water and nutrient-rich sediment that produce fertile soils, habitats for birds, spawning grounds for fish and natural irrigation that provides lush pastures for livestock (Sparks 1995).…”

Section: Characteristics Of Floodsmentioning

confidence: 99%

How Wetlands Affect Floods

2013

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It is widely recognised that wetlands play an important role in the hydrological cycle, influencing groundwater recharge, low flows, evaporation and floods. This has led to policies being formulated world-wide to conserve and manage wetlands to deliver these key services, especially flood risk reduction. Generic statements have often been published about wetland hydrological services but the term "wetlands" covers many land types, including wet woodlands, reedbeds, peat bogs, fens, and salt marshes. Each of these wetland types can have a hydrological function that is subtly different, making it difficult to generalise the flood reduction services of wetlands. In this paper we focus on two example wetland types (upland rain-fed wetlands and floodplain wetlands) to demonstrate why there are differences in flood functions both within and between wetland types. Upland wetlands generally tend to be flood generating areas while floodplain wetlands have a greater potential to reduce floods.2 However, landscape location and configuration, soil characteristics, topography, soil moisture status and management all influence whether these wetlands provide flood reduction services.

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“…Elephants (Loxodonta africana) form a major part of the wildlife resource in the Okavango Delta and contribute considerably to its ecological functioning (Mosepele et al 2009) as well as its economic sustainability (i.e. attractiveness to tourists).…”

Section: Introductionmentioning

confidence: 99%

Using simulations of past and present elephant (Loxodonta africana) population numbers in the Okavango Delta Panhandle, Botswana to improve future population estimates

Songhurst

Chase²,

Coulson

2015

Wetlands Ecol Manage

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An ability to reliably estimate population numbers, trends and densities of wildlife has a prominent role in conservation and management of wetlands. We use aerial surveys and simulation techniques to explore the results of past and present elephant population surveys in the Okavango Delta Panhandle, Botswana, and use these to propose a technique of simulation to improve counts in the future. Population numbers and density estimates from past survey results show large fluctuations, which are unlikely to come from reproduction. Reasons for such variations could be attributed to imprecision in survey techniques or may be because only part of the elephant range is being surveyed. Simulated surveys of hypothetical elephant populations were used to explore the effect of different survey techniques, spatial distributions of animals and spatial scale on the precision of aerial survey population estimates and trends. Our study reveals the usefulness of using simulations to test the reliability of survey data and plan more efficient surveys. We also find that while there may be some uncertainty in individual population estimates, there is more certainty in the recorded trends. These findings reinforce the need to address elephant management in the Okavango and surrounding wetland systems and call for the urgent consideration of management strategies such as fence realignments to affect the objectives of the Kavango Zambezi Transfrontier Conservation Area (KAZA TFCA) initiative, which will help relieve elephant population pressure.

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Fish, Floods, and Ecosystem Engineers: Aquatic Conservation in the Okavango Delta, Botswana

Cited by 99 publications

References 36 publications

Are Large Herbivores Vectors of Terrestrial Subsidies for Riverine Food Webs?

Are Large Herbivores Vectors of Terrestrial Subsidies for Riverine Food Webs?

How Wetlands Affect Floods

Using simulations of past and present elephant (Loxodonta africana) population numbers in the Okavango Delta Panhandle, Botswana to improve future population estimates

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