Agriculture Reference
In-Depth Information
all but small, specialized mammal herbivores. Renosterveld, in contrast, was
heavily impacted, presumably first by loss of megafauna, and then by cultivation
(Boucher & Moll
1981
). The largest impacts on fynbos in the past few centuries
have been indirect and the consequences of introductions of woody plants from
distant lands. Conifers were introduced for timber, Australian acacias for stabil-
izing sand dunes, and
Hakea
spp. for hedges. Many of these species are invasive
and pose the most direct threat to the continued existence of fynbos (Richardson
& van Wilgen
1986
). Extensive conifer plantations were established in higher
rainfall regions in the southwestern and southern Cape. The first intensive efforts
at fire management of fynbos were implemented to protect the plantations from
wildfires. Firebelts, sometimes extending more than a kilometre, are burned at
frequent intervals (
6 yrs) and adjacent fynbos stands are often burned to afford
additional protection. Increasing urbanization, as in all MTC regions, has frag-
mented fynbos so that large fires are now more likely to be contained. However,
fire sizes on the Cape Peninsula mountain chain, surrounded by the city of
Cape Town, have not changed significantly between the periods 1970-1988 and
1989-2007, while fire return intervals have apparently increased (Forsyth & van
Wilgen
2008
).
The human impact on fire regimes thus has a long history in the Cape region. It
is likely to have been relatively slight in the mountains because of their remoteness
and, with the exception of afforestation (planting forests), low utility for farming.
The second major mediterranean-type shrubland of the region, renosterveld, has
been so heavily converted that our knowledge of its ecology is fragmentary and
hopelessly incomplete.
Fire Management
The use of fire in managing fynbos has changed over the last century as a result of
changes in societal values and needs, scientific knowledge, and resources. In the
first few decades of the twentieth century, fires were burned to promote grazing.
This was followed by a period of fire suppression policy until the 1970s when
prescribed burning programs were initiated in the mountain catchment areas.
Since the mid 1980s, the areas burned in prescribed fires have declined, linked to
changes in state agencies managing the land (from forestry to conservation agen-
cies) and a decline in financial and human resources for managing fires. In more
remote areas, prescribed burning has been replaced by natural fire zones in which
attempts are made to suppress anthropogenic fires while allowing naturally ignited
fires to burn to their full extent (Seydack
et al.
2007
). Prescribed burning has also
become more difficult, especially near the wildland-urban interface (WUI),
because of legal and financial liabilities should fires burn beyond landowner
boundaries.
The principal management objective for prescribed burning in mountain
catchment areas has been to promote streamflow by reducing vegetation bio-
mass. Closely associated with this objective, fire is also used to manage alien
