Mai Po Logo: Pied Kingfisher |
|
 |
Deep Bay invaded by exotic mangroves
 
|
Over the past
few years, an exotic species of mangroves called Sonneratia
from south and south-east Asia has slowly been invading Deep
Bay. As with many other exotic species that has arrived at
a new site, they can have a tendency to grow and reproduce
very fast so eventually, dominating the local species. Sonneratia
is beginning to follow this tendency, since it has been reported
to be able to grow up to two metres in height in 2 to 3 years,
and trees have been recorded throughout the Deep Bay catchment
from the Shenzhen River and as far as Pak Nai. |
| Stand of Sonneratia
directly outside the border fence.. |
Due to their fast growth and ability to grow
in a variety of habitats, they have been used widely in southern China
as part of many coastal mangrove replanting schemes, even though they
are an exotic species. It is thought that the Sonneratia now in Deep
Bay may have come from the seeds dispersed by those same trees planted
elsewhere on the Mainland side of Deep Bay or around the Pearl River
Estuary.
The Agriculture, Fisheries and Conservation Department
(AFCD) has a programme to remove those trees which are found with the
Mai Po Inner Deep Bay Ramsar Site but the problem appears to be an
on-going one, with new trees appearing not long after the previous
trees have been removed. Furthermore, there are now many Sonneratia
trees growing amongst the mangroves and tidal channels outside of the
Ramsar Site, such as along the sides of the Shenzhen River. Apart from
their impacts on the ecology of the Deep Bay, there is also their potential
to obstruct the flow of water down these rivers during heavy rains
and typhoons, so increasing the risk of flooding in neighbouring low-lying
areas. Therefore, the matter of the arrival of Sonneratia should not
only be a concern for AFCD, but for other government departments such
as Drainage Services Department as well.
The
problem of Sonneratia is beginning to affect Mai Po Nature
Reserve (MPNR) as well. On 9 January 2004, several Sonneratia
trees were found growing outside of the Closed Area Fence
at MPNR by gei wai #7. Several of thee trees were up to
some 4m in height and some of the branches held flower
or were producing fruits. It is therefore urgent that government
devise an overall programme to remove these trees and those
around Deep Bay as soon as possible. |
|
| |
Flowering
branch, Sonneratia spp. |
|
