Barringtonia racemosa (L.) Roxb.
|Guava (a), Powder-puff Tree (e), Umululuka (z)|
Status and Criteria
|L. von Staden|
|Barringtonia racemosa is a widespread species, but it has a limited distribution on the east coast of South Africa, where it is localized to estuaries and the margins of freshwater lakes. It is fairly common in suitable habitat, and although there has been reported localized population decline in the past, it is not suspected to be in danger of extinction.|
|Not endemic to South Africa|
|Eastern Cape, KwaZulu-Natal|
|Coastal areas of eastern Africa, extending as far south as Pondoland, on the border between KwaZulu-Natal and the Eastern Cape. It extends to India, Thailand, northern Australia and islands of the south Pacific.|
Habitat and Ecology
|Subtropical Coastal Lagoons, Swamp Forest, Northern Coastal Forest|
|Streamsides, freshwater swamps and less saline areas of coastal mangrove swamps.|
|Barringtonia racemosa is sensitive to changes in water salinity in estuarine areas. Although it is associated with mangrove swamps, it does not have the high salt tolerance adaptation of true mangrove species (Osario et al. 2014), and therefore tends to occur somewhat further upstream (Macnae 1963). Infrastructure development and water abstraction often change the flow dynamics of tidal inundations of estuaries, resulting in mass die-back in populations of B. racemosa. Construction of the Richards Bay Harbour in the 1970s led to a 95% loss of the B. racemosa population around the Richards Bay Lagoon (Weisser and Ward 1982).
In the 1990s, prolonged drought conditions coupled with heavy water abstraction for industrial and domestic use resulted in the water in Lake Mzingazi, near Richards Bay, to reach salinity levels close to that of sea water (Cyrus et al. 1997). This caused severe salt-stress and die-back of the swamp forest up to 15 meters from the river bank, but no mortality of B. racemosa was observed (Cyrus et al. 1997).
Estuaries are highly dynamic ecosystems, and Jimenez and Lugo (1985) suggests that mangrove species are adapted to rapid changes in environmental conditions such as salinity fluctuations and periodic flooding. This is due to their ability to quickly recolonise areas affected by die-back when conditions become suitable again, by means of ocean-dispersed drift seeds (Prance 2012).
B. racemosa thrives in freshwater coastal swamps that form when rivers become closed off from the sea, and often becomes the dominant species in such habitats (Macnae 1963). In many smaller rivers, upstream damming and water abstraction, which leads to reduced flow and more frequent and prolonged closed-mouth conditions, may be increasing available habitat for B. racemosa, to the detriment of other true mangrove species (Rajkaran et al. 2009).
Other threats to B. racemosa include fungal disease, which cause fruit abortion (Osario et al. 2015), and climate change induced sea-level rise (Naidoo 2016). Although mangroves are adapted to shift inland with sea-level rise, widespread coastal development presents a barrier to dispersal. Chemical pollution of estuarine water occurring close to harbours and large cities such as Durban and Richards Bay is an ongoing threat (Naidoo 2016), and may be a contributing factor to mangrove die-back observed in these areas.|
B. racemosa is widespread along the KwaZulu-Natal coast, but is a highly localized habitat specialist, with an estimated national AOO of <100 km². It is known from at least 16 locations, which are mainly estuaries, but also swamp forests surrounding freshwater lakes in the Maputaland region. Although there has been reports of past declines in B. racemosa subpopulations, it is also able to recover and re-establish after die-back. The current population trend is not known, but is suspected to be either fluctuating or increasing, particularly in smaller estuaries on the KwaZulu-Natal South Coast. Globally, Barringtonia racemosa is the most widespread and common species in the genus (Prance 2012), and is widely dispersed by means of drift seeds.
|von Staden, L. 2016. Barringtonia racemosa (L.) Roxb. National Assessment: Red List of South African Plants version 2017.1. Accessed on 2019/12/11|