The case for environmental flow determination for the Phongolo River,South Africa

The construction of Pongolapoort Dam in 1973 on the Phongolo River in KwaZulu-Natal, South Africa, has considerably altered the hydrological behaviour and ecological response of the downstream floodplain. Changes in the flooding regime have had implications for the socio-economic importance of the floodplain and for the structure and functioning of its associated wetlands. Previous studies have recommended annual releases of water from the dam to sustain floodplain ecosystem goods and services. The current artificial water releases are limited by the size of the dam's sluices and by the demand for water from the local community. Therefore, water releases do not always follow the original natural flooding regime. To date, the influence of the changed hydrology on the ecology of the Phongolo floodplain system remains poorly known. As a basis for future integrated interdisciplinary research we synthesised the ecological and hydrological work conducted to date on the Phongolo floodplain. We suggest hydro-ecology as an important research direction needed to set environmental flows for the sustainable utilisation and management of the floodplain. Understanding the hydrological behaviour and ecological response of the Phongolo floodplain could help in the implementation of environmental flows by managers at the Department of Water and Sanitation and other stakeholders such as Ezemvelo KZN Wildlife.     

Long-term landscape changes in vegetation structure: fire management in the wetlands of KwaMbonambi,South Africa

In wetlands the effects of fire on vegetation dynamics are somewhat uncertain. A change detection analysis in the herbaceous wetlands of KwaMbonambi, South Africa, which were subject to frequent fires, revealed that in 1937 the study area comprised grassland (69%), herbaceous wetland (25%), indigenous swamp forest (4%) and tree plantations (1%). However, by 1970, tree plantations occupied 78% of the landscape and grasslands and herbaceous wetlands had declined to 9% and 6%, respectively, whereas indigenous swamp forest had increased to 6%. By 2009 tree plantations had been removed from the wetland areas. Despite this opportunity for herbaceous wetlands to recover their historical extent, they decreased to only 2%, mostly changing to indigenous swamp forest or to an herbaceous/fern (Stenochlaena tenuifolia)/woodland mosaic. Fire records showed suppression of fire to be an important contributing factor, particularly in wetlands that had been disturbed by tree plantations, although subsequently removed. A pilot burning experiment revealed that S. tenuifolia did not inhibit fire. It is therefore practicable to increase fire frequency to prevent the mosaic developing into forest. A conceptual model of the influence of fire regime on wetland vegetation type is presented and priorities for further research on wetlands and fire are recommended.     

Reproduction in Schlieffen's bat, Nycticeius schlieffenii, in the eastern Transvaal lowveld, South Africa

The present study is based on 153 Schlieffen's bats collected over a 2-year period from September 1983 to September 1985. Spermatogenesis extends over a 10-month period with the first signs of spermatozoa in the epididymides by the end of April. Spermatozoa were present in the epididymides from the end of April until the beginning of September. Copulation begins during June (early winter) and the females have spermatozoa in the uterine horns from then until the end of August (late winter) when ovulation occurs. These bats are seasonally monoestrous with the great majority of births occurring during November. The number of conceptuses varied; a maximum of 5 pre-implanted embryos was recorded, but the maximum number of fetuses observed was 3.     

The rediscovery of Albuca tenuifolia,an orophilous species from the eastern Great Escarpment in South Africa

Albuca tenuifolia Baker was described and illustrated in 1872 from South African material sent by Peter MacOwan to William Wilson Saunders in England, without a precise locality. Since then this species has been cited in later works although with many uncertainties. In addition, no type has been designated for this taxon. After field work in the Great Escarpment in South Africa, some populations of A. tenuifolia have been rediscovered growing in rocky places at high altitude. Data on morphology, ecology, and distribution are reported, and a lectotype and epitype are designated to fix the use of the name. Affinities with other species are also discussed.     

Hierarchical spatial organization and prioritization of wetlands: a conceptual model for wetland rehabilitation in South Africa

Wetland rehabilitation planning needs to take into account many different aspects of the wetland and its context. In South Africa, much emphasis is placed on the delivery of ecosystem services, poverty relief and skills development for those involved in labour-intensive rehabilitation measures. A framework is presented that facilitates decision-making with regards to wetland rehabilitation planning. This starts with prioritizing which wetlands need attention within a catchment. This is followed by decisions regarding which rehabilitation measures would be effective in improving certain ecosystem services based upon the aims of rehabilitation and the social context of the surrounding catchment. The functional unit that is most suitable to work with for rehabilitation is the Hydrogeomorphic (HGM) Unit, defined as a section of a wetland with more or less uniform hydrological and geomorphological characteristics. An individual wetland may comprise several HGM units, and a HGM Unit itself can be sub-divided into several smaller habitat or vegetation units. Different rehabilitation measures have been identified which are appropriate for the different scales in this spatial framework. Two case studies are presented as examples of how this spatial framework impacts upon the decisions made by the rehabilitation practitioner.     

The impact of river regulation on the biodiversity intactness of floodplain wetlands

Alteration of natural flow regime is considered a major threat to biodiversity in river floodplain ecosystems. Measurements of quantitative relationships between flow regime change and biodiversity are, however, incomplete and inconclusive. This hampers the assessment of human impact on riverine floodplain wetlands in global biodiversity evaluations. We systematically reviewed the scientific literature and extracted information from existing data sets for a meta-analysis to unravel a general quantitative understanding of the ecological consequences of altered flow regimes. From 28 studies we retrieved both ecological and hydrological data. Relative mean abundance of original species (mean species abundance, MSA) and relative species richness were used as effect size measures of biodiversity intactness. The meta-analysis showed that alteration of a natural flow regime reduces the MSA by more than 50 % on average, and species richness by more than 25 %. Impact on species richness and abundance tends to be related to the degree of hydrological alteration. These results can be used in strategic quantitative assessments by incorporating the relationships into global models on environmental change and biodiversity such as GLOBIO-aquatic.     

Global scale variation in the salinity sensitivity of riverine macroinvertebrates: eastern Australia, France, Israel and South Africa

Salinity is a key abiotic property of inland waters; it has a major influence on biotic communities and is affected by many natural and anthropogenic processes. Salinity of inland waters tends to increase with aridity, and biota of inland waters may have evolved greater salt tolerance in more arid regions. Here we compare the sensitivity of stream macroinvertebrate species to salinity from a relatively wet region in France (Lorraine and Brittany) to that in three relatively arid regions eastern Australia (Victoria, Queensland and Tasmania), South Africa (south-east of the Eastern Cape Province) and Israel using the identical experimental method in all locations. The species whose salinity tolerance was tested, were somewhat more salt tolerant in eastern Australia and South Africa than France, with those in Israel being intermediate. However, by far the greatest source of variation in species sensitivity was between taxonomic groups (Order and Class) and not between the regions. We used a bayesian statistical model to estimate the species sensitivity distributions (SSDs) for salinity in eastern Australia and France adjusting for the assemblages of species in these regions. The assemblage in France was slightly more salinity sensitive than that in eastern Australia. We therefore suggest that regional salinity sensitivity is therefore likely to depend most on the taxonomic composition of respective macroinvertebrate assemblages. On this basis it would be possible to screen rivers globally for risk from salinisation.     

Linking riparian vegetation types and fluvial geomorphology along the Sabie River within the Kruger National Park, South Africa

Vegetation types were studied in relation to the fluvial geomorphology along the mixed bedrock‐alluvial Sabie River within the Kruger National Park, Mpumalanga, South Africa. Six vegetation types were identified using TWINSPAN analysis, namely: Phragmites mauritianus , Phyllanthus reticulatus , Breonadia salicina , Combretum erythrophyllum , Diospyros mespiliformis and Spirostachys africana vegetation types. Spirostachys africana and Diospyros mespiliformis vegetation types were found to occur predominantly on the stable, infrequently flooded macro‐channel banks, while the remaining four vegetation types were found almost exclusively along the more geomorphically and hydrologically dynamic macro‐channel floor. The degree of bedrock or alluvial influence was identified as being an integral factor in the distribution of the four macro‐channel floor vegetation types at both the morphological unit and the channel type scale. The geomorphological continuum from the bedrock influenced bedrock anastomosing channel types, to mixed anastomosing and pool‐rapid channel types, to the fully alluvial braided channel types, is reflected in the change in species composition from Breonadia salicina vegetation type, to Phyllanthus reticulatus and Phragmites mauritianus vegetation types, to Combretum erythrophyllum vegetation types, respectively. Given the vegetation/fluvial geomorphology links established, changes in vegetation composition are proposed in response to scenarios of geomorphological change as a result of progressive sedimentation.     

Macroinvertebrates as unreliable indicators of human disturbance in temporary depression wetlands of the south-western Cape, South Africa

Macroinvertebrates have a successful history of use as indicators of human impact in lotic environments. More recently, macroinvertebrate indices have been recommended for use in certain wetland types. Yet some authors do not recommend macroinvertebrates indices of wetland condition in areas with pronounced natural environmental heterogeneity. Our study provides a preliminary assessment of the feasibility of using macroinvertebrates for bioassessment of temporary isolated depression wetlands in the south-western Cape region of South Africa. We expected natural environmental heterogeneity among wetlands to exert a stronger influence on macroinvertebrates than human disturbance factors. Partitioning of the variation in macroinvertebrate assemblage composition that could be attributed to human disturbance factors (within and adjacent to wetlands), environmental variables and spatio-temporal factors indicated that environmental and spatio-temporal factors independent of human disturbances largely determined assemblage composition, whilst human disturbance played a relatively minor role. Linear regressions of taxon richness/diversity measures, individual families and a collation of metrics against measures of habitat transformation around wetlands and scores from a rapid assessment index of human disturbance revealed poor relationships. The univariate and multivariate patterns observed in this study do not lend themselves to the creation of a macroinvertebrate index of human disturbance for temporary wetlands in the region.     

The role of domestic herbivores in endozoochorous plant dispersal in the arid Knersvlakte,South Africa

Herbivores can act as dispersal vectors by purposely or accidentally ingesting ripe fruits, and thus endozoochory is one determining factor for plant distribution patterns. The objective of our study was to investigate to what extent plants of major taxonomic groups of the Knersvlakte (Succulent Karoo, South Africa) are endozoochorously dispersed. On three different farms in the central Knersvlakte, dung of domestic herbivores was collected and analysed by the seedling-emergence method. The resulting species composition was compared to the standing vegetation of thirty-four 1000-m² plots each recorded on one hundred 400-cm² subplots. Our results show that domestic livestock facilitated the dispersal of taxa characteristic of the Knersvlakte, in particular Aizoaceae. Among the taxa of this family, the local endemic dwarf shrub Drosanthemum schoenlandianum emerged with the highest frequency in dung (14.5% of all seedlings). For the Asteraceae, which are frequent in the standing vegetation of the Knersvlakte, however, endozoochorous dispersal by livestock was only of minor importance. Conservation planning should consider these dispersal patterns on behalf of future population dynamics. The complete exclusion of livestock might change current processes and thus alter vegetation patterns.     

Refugia, dispersal and divergence in a forest archipelago: a study of Streptocarpus in eastern South Africa

We describe a scenario of plant speciation across a relict forest archipelago in South Africa involving Pleistocene habitat expansion-contraction cycles, dispersal and adaptation to lower temperatures. This is the first population level study using molecular data in South African forests and has significant implications for conservation efforts in this area. Populations of the mesophytic forest floor herbs Streptocarpus primulifolius sensu lato and Streptocarpus rexii were sampled throughout their range in the naturally fragmented forests of eastern South Africa in order to investigate population genetic and phylogenetic patterns within the species complex, using nuclear microsatellites, nuclear ribosomal ITS (internal transcribed spacer) sequences and chloroplast genome sequences. S. primulifolius harbours high levels of genetic diversity at both the nuclear (mean HE = 0.50) and the chloroplast level (each population fixed for a unique haplotype). This is consistent with populations of these coastal species being Pleistocene relicts. In contrast, populations of S. rexii in cooler habitats at higher altitudes and lower latitudes harbour little or no nuclear genetic diversity (mean HE = 0.09) and most share a common chloroplast haplotype. The split of S. rexii from populations intermediate between the two species (S. cf. primulifolius) occurred between 0 and 0.44 million years ago according to the calibrated ITS phylogeny of the taxa. The low genetic diversity and homogeneity of S. rexii is congruent with this species having reached its current range during the Holocene. We found no evidence of monophyly of any of the taxa in this study, which we consider a consequence of recent evolution in a fragmented habitat.     

The role of herbivores in the collapse of the Gracilaria resource at Saldanha Bay,South Africa

At Saldanha bay on the west coast of South Africa, annual yields of beach-cast Gracilaria often exceeded 1000 metric tons, until the construction of an ore jetty and breakwater in 1974. Yields were then drastically reduced, recovered to 429 tons in 1988, then fell to zero. Diving surveys revealed a steady decline in the biomass of the remaining beds from 50 t in April to less than 1 t in August 1989. The presence of large numbers of herbivores suggested that grazing was the cause. This hypothesis was tested by experimental exclusions of fish and/or invertebrate herbivores (keyhole limpets and sea urchins). Results show that grazing by the fish in shallow water and the keyhole limpets and urchins in deep water prevented recovery of the resource and may have caused the initial decline.     

Towards the development of a macroinvertebrate sampling technique for palustrine wetlands in South Africa: a pilot investigation in the KwaZuluNatal midlands

A study was undertaken in November 2003 to derive a suitable sampling technique for collecting a representative sample of aquatic macroinvertebrates from a selected emergent vegetation biotope in a palustrine wetland, Melmoth Vlei, KwaZulu-Natal, South Africa. The aim was to undertake a preliminary investigation on the development and testing of a macroinvertebrate sampling technique for use in emergent sedge-dominated palustrine wetlands (sensu Cowardin et al. 1979), which could contribute to the development of a South African wetland health biomonitoring programme. Sweep nets and activity traps were evaluated for their effectiveness in terms of macroinvertebrate collection. Sweep net sampling was tested over a range of sweep intensities to determine the minimum number of sweeps required to collect a representative sample. Sampling efficiency of activity traps placed at four depths was tested, and taxon diversity and composition of sweep net and activity trap samples were compared to determine whether activity traps are required to supplement sweep net data. A total of 32 taxa (identified mainly to family level) were identified in the samples collected. Taxon diversity and composition did not differ in the activity traps placed at the four depth locations. Taxon diversity did not differ significantly between different sweep intensities. This may be a result of high variability of macroinvertebrate distribution within a wetland. There is evidence, however, to suggest that this result is due to an inadequate sample size. There was a significant difference in taxon composition between the different sweep intensities (P < 0.05) and between activity trap and sweep net samples (P < 0.05). Sixty-eight percent of taxa appeared more frequently in sweep net sampling than in activity trap sampling. Two taxa were found exclusively in activity traps, although the numbers of these taxa collected were not significant, and they do not represent any unique trophic group. Based on these findings, it was concluded that activity traps are not required to supplement sweep net data, and a technique using a sweep net with a sweep intensity of five would be suitable for collecting a representative sample of macroinvertebrates from a palustrine wetland.     

Defining a role for herbarium data in Red List assessments: a case study of Plectranthus from eastern and southern tropical Africa

Red Lists are widely used to indicate species at risk of extinction. Specimen sheets in herbaria provide an important source of data relevant for Red List assessments. The aims of this paper are to establish which data can be sourced from specimen information to satisfy IUCN Red Data List criteria and to identify the specific criteria that can be used. Red List parameters are measured within a Geographical Information System (GIS), as this provides an objective and repeatable methodology which is less subjective than manual methods. Data used to explore this were gathered during the course of preparing a monograph on Plectranthus (Lamiaceae). Criteria relating to distribution (extent of occurrence, area of occupancy and fragmentation) and population profile (projected continuing decline and number of subpopulations) proved most suitable for assigning categories of threat. Estimates of mature individuals, generation length, population size, population reduction, extreme fluctuation and number of locations could not be derived from herbarium material without making inconsistent subjective decisions. In addition to comprehensively databased specimen information, extensive field knowledge is required to produce better estimates for assessing extinction risk. In order to enhance the usefulness of specimen information in the future, improvements in recording additional botanical data at the time of collection would be beneficial. Overall, herbaria provide a useful starting point for conservation-related work and can help to guide future work.     

Changes in plant form and function across altitudinal and wetness gradients in the wetlands of the Maloti-Drakensberg,South Africa

A survey of 93 wetlands in six catchments across the Maloti-Drakensberg is used to assess the distribution of plant functional types across altitudinal and wetness gradients. Altitudes range from 1,000 to 3,200 m a.s.l. Within each catchment, the wetlands were selected to cover the complete range in altitude and wetland types. In each of the selected wetlands, vegetation was sampled in 3 by 3 m quadrats covering the entire range of wetness represented in the wetland, from temporarily wet to permanently inundated soils. Plant species were allocated to one of 11 different functional types (examples are C₃ grasses, C₄ sedges, rosette plants, and shrubs), and the proportion of the vegetation in each sample occupied by each functional type was calculated from the species’ abundances. Canonical Correspondence Analysis shows that “wetness” clearly has the highest impact on the distribution of functional types, followed by altitude. The most important plant functional types in wetlands are grasses and sedges, however, at higher altitudes, forbs (especially rosette plants) and bulbous plants become a more prominent feature in the wetlands. The total amount of graminoids gradually decreases with altitude. The general trend is that sedges tend to increase with increasing wetness and C₃ plants (grasses and sedges) increase with increasing altitude, but these effects are not independent. The distributions of C₄ sedges and C₄ grasses along an altitudinal gradient are quite different, and C₄ grasses grow abundantly at much higher altitudes than C₄ sedges. C₄ sedges are very scarce at the altitudes represented in the Maloti-Drakensberg area, whereas C₃ grasses occur in the permanently wet parts of the wetlands, especially at higher altitudes (normally mostly occupied by sedges). Shrubs are rare in wetlands and tend to be an indication of disturbance. This study complements previous studies on the distribution of grasses and sedges at the lower altitudes within KwaZulu-Natal, which found that at altitudes below 1,000 m a.s.l. C₄ sedges were much more prominent, while forbs and rosette plants were largely absent. This confirms that C₄ as an adaptation to hotter and warmer climates is sometimes a less favorable metabolism in wet high altitude areas. At high altitudes, rosette plants and bulbous plants become more competitive in wetlands, probably because grasses and sedges present at these altitudes generally grow smaller than they do in low altitude wetlands.     

The World Crane Action Plan: implications for conservation of cranes and wetlands in Africa

Beilfuss, R.D., Meine, C.D., & Archibald, F.W. 2000. The World Crane Action Plan: implications for conservation of cranes and wetlands in Africa. Ostrich 71 (1 & 2): 227.

The IUCN Species Survival Commission recently published The Cranes: Status Survey and Conservation Action Plan. Prepared over the past three years by the IUCN Crane Specialist Group, the document reviews the status of the world's cranes (Family: Gruidae) and their habitats, summarises recent crane conservation actions, and specifies priority measures for the future. Eleven of the 15 crane species are now proposed for inclusion on the IUCN Red List of Threatened Animals, and several subspecies and populations are critically endangered. Africa supports six species of cranes in 39 countries. The Black Crowned Crane Balearica pavonina, national bird of Nigeria, is resident in western and central Africa. The Grey Crowned Crane B. regulorum, national bird of Uganda, spans eastern and southern Africa. The Wattled Crane Bugeranus carunculahrs, largest and. rarest of Africa's cranes, ranges from Ethiopia to South Africa. The Blue Crane Anthropoides paradiseus, national bird of South Africa, is endemic to South Africa and Namibia. The Demoiselle Crane A. Virgo and Eurasian Crane Grus grus are winter visitors. Cranes have been the focus of intensive captive propagation and reintroduction programs as well as extensive habitat protection efforts. They are also excellent umbrella species for ecosystem-level conservation efforts. Wetlands that provide a home for cranes include the floodplains of the great river systems of Africa, such as Kafue Flats and Zambezi Delta of the Zambezi River system, the Okavango River Delta, the Sudd of the Upper Nile River, the Bangweulu Basin and swamps of the Zaire River system, the Senegal River Delta, and the Inner Niger River Delta, and the wetlands of Lake Chad. Small, isolated wetlands provide vital breeding habitat. This presentation will provide an overview of the action plan for those interested in cranes in particular, as well as those working in ecosystems and regions where cranes occur.     

Reproduction in females of the little free-tailed bat, Tadarida (Chaerephon) pumila, in the eastern Transvaal, South Africa

Little free-tailed bats (2-9/month) were collected over 15 months in the eastern Transvaal lowveld (latitude 24 degrees 59'S). There was an extended but distinct breeding season of 8 months per year. Females appeared to be polyoestrous and able to bear 3 pregnancies per breeding season. There was a progressive decrease in the magnitude of the three birth peaks during the breeding season, with a concomitant slight loss in birth synchronization. Gestation period was approximately 60 days and one young per female was the rule, with implantation occurring only in the right uterine horn of the bicornuate uterus. It is suggested that offspring are weaned before the age of 21 days, and that female become sexually mature in the following breeding season at the age of 5-12 months.