Download Ecological Response to Storms

Ecological
response to storms
Storms elicit an erosion response from the visible portion of all beaches, even the healthy ones. The important thing to
remember though, is that most sand is not lost, just put somewhere else within the system. For more information
about the beach’s physical response to storms, check out Beach erosion and coastal processes on the Gold Coast
information sheet. This information sheet examines the ecological response of the coastal environment to storms.
The coastal environment is extraordinarily dynamic. Much habitat can be lost, altered or created in a large storm event.
As a result, species composition in these environments tends to fluctuate.
The importance of
vegetation
The integrity of the sand supply on
the visible portion of the beach is
dependent upon vegetation. This
vegetation traps windblown sand,
thereby facilitating accretion and
the growth of the sand dune, see
Figure 1. Vegetation slows down
sand particles blown landward by
wind, leading to deposition and
accumulation of dunes. Without this
vegetation, sand will be blown
further inland, resulting in a net
loss in the sediment budget and a
retreating coastline.
Figure 2. Ghost Crab (Ocypode cordimanus)
(Source: GCCC 2011)
Dune plant colonisation
Build-up of sand
Healthy dune system
Figure 1. The process of sand dune formation (GCCM 2011)
What about the beach fauna?
Disturbances such as storms can have a great effect on the dune and beach
fauna. Erosion to the dunes can displace many animals, including crustaceans,
reptiles and birds. Naturally, animals would have an opportunity to move
away from the eroding escarpment; however, such disturbances in our urban
environment can leave them temporarily displaced.
Erosion of the sandy beach can lead to the decline in invertebrate populations.
There appears to be very few studies of the recovery rates of these
invertebrate populations; however, it is known that these invertebrates
usually number in the millions, so recovery can be rapid. This recovery is also
boosted by an opportunistic immigrant population, which will move in after a
storm event to take advantage of reduced levels of competition or predation.
Plant succession: the key to recovery from storms
Plant succession occurs in response to a disturbance (for example, a storm) and refers to a process of change over time
within the ecological community. After a disturbance, particular plant species first colonise the disturbed space followed
by a succession of further plant types until the plant community has recovered.
Colonising species
♦ Hardy pioneers that survive within the inhospitable, newly formed dunes
♦ Tolerate exposure, poor nutrient conditions, a lack of fresh water and sometimes
very high temperatures (McLachlan & Brown, 2006)
♦ Create the structure of the dunal habitat by reducing wind erosion, increasing
soil moisture and also increasing nutrient stores within the sand
♦ Example: Spinifex grass (Figure 3), which after a storm hangs over the erosion
scarp and starts trapping wind-blown sand
Secondary species
♦ Less tolerance to exposure and greater nutrient requirements
♦ Cope with poor water availability and high temperatures
♦ Example: Coastal Wattle, which disperses readily and has in-built mechanisms
Figure 3. Sand Spinifex is a valuable
coloniser of Gold Coast dunes
(Source: GCCC 2006)
to cope with water stress (Figure 4)
Climax communities
♦ Characterised by mature vegetation, typically dominated by larger, long-lived
trees such as Eucalypts, or Pandanus Palm (Figure 5)
♦ Takes much longer to recover from large storm events
Our changing coast
Storm events are a natural element of the coastal environment. Given time,
ecosystems affected by a storm event will recover through processes such as
succession. It is important that Council’s coastal management activities work with
rather than against these natural processes, and that any management activities
do not reduce the ability of natural ecosystems to respond to storm events.
Figure 4. Coastal wattle on South
Stradbroke Island (Source: GCCC 2007)
For more information about these
coastal environments, refer to
information sheets in the
Discovering our Coast series.
A healthy dunal system
The structural composition of dune vegetation can tell us a lot about the capacity of the
ecosystem to respond to a storm event. The presence of colonising species in the fore
dunes is a good sign that these oceanfront dunes would be stabilised quickly following a
storm disturbance event. In contrast, if the hind dunes experience direct exposure to a
storm event, their vegetation composition is less resilient to harsh conditions and recovery
is expected to be slower. This is one of the reasons why healthy dune systems feature a
combination of fore dunes, secondary dunes and hind dunes – the space gives the beach
flexibility to move in accordance with the sand store, and maximise its ability to
ecologically and structurally recover from storm events.
Figure 5. Established Pandanus
Palm on South Stradbroke
Island (Source: GCCC 2007)
References:
Mahony, D. 1978, Beaches: Learning to Live with the Sea. Charden Publications, Summer Hill.
McLachlan, A. and Brown, A. 2006, The ecology of sandy shores. Academic Press, Massachusetts.