Recovery of South African fynbos vegetation following alien woody plant clearing and fire: implications for restoration

Holmes, Patricia M.; Richardson, David M.; Wilgen, Brian W. van; Gelderblom, Caroline

doi:10.1046/j.1442-9993.2000.01063.x

Cited by 25 publications

(29 citation statements)

References 17 publications

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“…At current rates of clearing, infestations of several important species would be cleared only within 30-85 years. 54 This estimate is based on a number of assumptions, each of which reduces the estimate of time needed to clear existing infestations; the estimates are therefore probably serious underestimates. These assumptions include: (1) that infestations are static, and will not spread further while clearing operations are under way; (2) that clearing a site will eradicate the invasive alien species; (3) that areas require only one followup treatment; (4) that funding levels will remain at the levels sustained over the past few years; and (5) that we know how big the problem is.…”

Section: Prognosis For Invasive Alien Plant Controlmentioning

confidence: 99%

“…While the first two methods can be used to contain infestations, neither provides a permanent or sustainable solution to the problem. 54,55 Biological control options provide more sustainable solutions, but are only available for some of the invasive alien plant species in the fynbos. 56 Hakeas and several wattles have a suite of seed-feeding and gall-forming insects which can reduce seed loads.…”

Section: Invasive Alien Plants In Fynbos Ecosystemsmentioning

confidence: 99%

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The evolution of fire and invasive alien plant management practices in fynbos

Wilgen¹

2010

S Afr J Sci

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Section: Prognosis For Invasive Alien Plant Controlmentioning

confidence: 99%

Section: Invasive Alien Plants In Fynbos Ecosystemsmentioning

confidence: 99%

The evolution of fire and invasive alien plant management practices in fynbos

Wilgen¹

2010

S Afr J Sci

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“…The risks of damage to property and the loss of human lives or severe injuries are also greatly increased. The severe fires also kill seeds in the soil and sprouting plant species (Richardson and van Wilgen, 1986;Holmes et al, 2000).…”

Section: Other Benefitsmentioning

confidence: 99%

Invasive alien trees and water resources in South Africa: case studies of the costs and benefits of management

Maitre¹,

Wilgen²,

Gelderblom³

et al. 2002

Forest Ecology and Management

240

136

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Invasive alien plants are consumptive water-users, and may have reduced river flows in South Africa by about 6.7% according to a broad-scale study. An effective programme to bring the invasions under control would cost about US$ 92 million per year for the next 20 years. This paper reports on studies of four representative catchments (the Sonderend, Keurbooms, Upper Wilge and Sabie-Sand) to assess the impacts and costs of invasions at a scale that is more relevant to managers. Several alien plant species have invaded the catchments. Non-riverine invasions are mainly Pinus and Hakea species in Sonderend and Keurbooms, eucalypts in the Upper Wilge, and pines and scramblers (e.g. Lantana camara) in the Sabie-Sand catchment. Riverine invasions are dominated by Acacia mearnsii and, to a lesser extent, A. dealbata, except in the Sabie-Sand and the lower Sonderend River where Eucalyptus species are important. About 44% of the Sonderend, 54% of the Keurbooms, 2% of the Upper Wilge and 23% of the Sabie-Sand catchments has been invaded to some degree. The corresponding reductions in the natural river flows attributed to these invasions are about 7.2, 22.1, 6.0 and 9.4%. If the invasions are not controlled they could potentially spread, and occupy 51, 77, 70%, respectively, of the first three catchments. At an annual expansion rate of 10-15% this would take about 13, 26 and 63 years, respectively. The invadable areas in the Sabie-Sand catchment are already invaded so invasions will only increase in density. It would take about 26-30 years to reach 100% canopy cover. The projected flow reductions for the four catchments would increase to 41.5, 95.5, 25.1 and 22.3%, respectively. The estimated cost of the control programmes to prevent these losses would be about US$ 13.2, 9.9, 4.1 and 6.6 million for the Sonderend, Keurbooms, Upper Wilge and Sabie-Sand catchments, respectively. Should the catchments be allowed to become fully invaded before control operations were started, then the costs would rise to US$ 86.5, 20.5, 278.0 and 11.1 million, respectively. The impacts and costs are significant and are comparable with those calculated independently for other South African catchments. Water is acknowledged to be a key constraint to economic growth in South Africa and there is considerable pressure for efficient and sustainable use of the limited water resources. The projected impacts would justify control programmes aimed at clearing alien invaders for water conservation. #

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“…The total area (ha) occupied by Hakea sericea infestations in three density categories (see Table 1 Holmes et al 2000). On the other hand, much smaller areas experienced an increase in the density of invasion, with 2,500 ha going from absent to high, and ~20,000 ha going from either absent to moderate, or low to high.…”

Section: Tablementioning

confidence: 99%

A landscape-scale assessment of the long-term integrated control of an invasive shrub in South Africa

Esler

Wilgen²,

Roller

et al. 2009

Biol Invasions

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The control of invasive alien plants often involves the integration two or more approaches, including mechanical clearing, the application of herbicides, burning, and biological control. More than one species of invasive plant can threaten the same area, which necessitates prioritization in the allocation of scarce resources to support the control of different species. This paper describes the integrated control of the invasive shrub Hakea sericea over four decades in South Africa. The species is widespread across an area of approximately 800 × 200 km, and occurs mainly in rugged, inaccessible and fire-prone mountain areas. The species is serotinous, and produces copious amounts of seed that are wind dispersed after fires. We present a brief history of the control measures which included a combination of felling and burning, augmented by biological control. We used data from two surveys, 22 years apart, to assess changes in distribution and density of the species. The assessment suggested that the overall distribution of the species was reduced by 64%, from ~530,000 to ~190,000 ha between 1979 and 2001. The species either decreased in density, or was eliminated from 492,113 ha, while it increased in density, or colonised 107,192 ha. We conclude that initial programs of mechanical clearing were responsible for reducing the density and extent of infestations, and biological control was largely responsible for the failure of the species to recolonize cleared sites, or to spread to new areas following unplanned wildfires. We propose that a significant portion of the resources used for clearing Hakea in the past can be reallocated to mechanical control efforts against other invasive species (such as alien pines) for which effective biological control options are not available, provided that sufficient resources are allocated to ensure the widespread and effective implementation of all biological control agents to maintain the advances reported on here.

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Recovery of South African fynbos vegetation following alien woody plant clearing and fire: implications for restoration

Cited by 25 publications

References 17 publications

The evolution of fire and invasive alien plant management practices in fynbos

The evolution of fire and invasive alien plant management practices in fynbos

Invasive alien trees and water resources in South Africa: case studies of the costs and benefits of management

A landscape-scale assessment of the long-term integrated control of an invasive shrub in South Africa

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