State of the Bay Report 2011-Final.pdf - Anchor Environmental

No. saltmarsh patches
Saltmarsh area (million m 2 )
State of Saldanha Bay & Langebaan Lagoon 2011
Aquatic macrophytes
6.2 Long term changes in Saltmarshes in Langebaan Lagoon
Saltmarshes in Langebaan are reportedly an important habitat and breeding ground for a range of
fish, bird and invertebrate species (Christie 1981, Day 1981, Gerrike 2008). Langebaan Lagoon
incorporates the second largest salt marsh area in South Africa, accounting for approximately 30% of
this habitat type in the country, being second only to that in the Knysna estuary (Allanson et al.
1999).
Long term changes in salt marshes in Langebaan Lagoon were investigated by Gerrike (2008)
using aerial photographs taken in 1960, 1968, 1977, 1988 and 2000. He found that overall saltmarsh
area had shrunk by only a small amount between 1960 and 2000, losing on average 8 000 m 2 per
annum. Total loss during this period was estimated at 325 000 m 2 , or 8% of the total (Figure 6.3,).
Most of this loss has been from the smaller patches of salt marsh that existed on the seaward edge
of the main marsh. This is clearly evident from the change in the number of saltmarsh patches in the
lagoon over time, which has declined from between 20 and 30 in the 1960s and 70s to less than 10
at present. Gerrike (2008) attributed the observed change over time to increases in sea level that
would have drown the seaward edges of the marshes or possibly reduced sediment inputs from the
terrestrial edge (i.e. reduced input of windblown sand due to stabilization by alien vegetation and
development).
20
15
10
5
0
1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005
Figure 6.3. Change in saltmarsh area over time in Langebaan Lagoon. (Data from Gerricke 2008)
30
25
20
15
10
5
0
1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005
Figure 6.4.
Change in the number of discrete saltmarsh patches over time in Langebaan Lagoon. (Data
from Gerricke 2008)
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