8 IMPACTS ON MANGROVES

8.1 Types of adverse impact

Some of the key impacts on Egypt’s mangroves have been highlighted by Dar (2002). Based on that paper, Saenger (2002) and site visits as part of this study, the types of impact associated with mangroves in Egypt can be summarised, as shown on Table 13. The table also highlights the different types of value that are most at risk from direct and indirect impact.

Table 13 Impacts on Egypt’s mangroves and key values affected

Of the direct impacts, the most serious impacts in the past have been clearance for hotels and development and excessive cutting for boat building (from anecdotal sources). However, these activities have been curtailed because of the legal protection.

Perhaps the most significant current direct impact is camel browsing. This seems to be a major problem at one site, El-Hamirah, the line above which camels cannot reach is clearly visible (Photo 10 and Photo 11). The extensive trampling effect of the camels may also have helped cause a ponding effect. However, it may be that the mangroves can recover adequately once the browsing pressure is lifted. The bare looking mangroves are not dead, but do have much new growth of leaves close to the main stems. This browsing is perhaps only a real problem if it continues to get worse. The mangroves are actually playing an important role at El-Hamirah through providing fodder in times of a drought.

There seems to be a concerning degree of illegal cutting of mangroves for camel fodder, building purposes and possibly charcoal (Dar, 2002). However, there is little data available on this. If undertaken on a sustainable basis, this activity can be supported in the long term by mangroves. However, when undertaken excessively in relatively small stands of mangroves, it can lead to rapid loss of mangrove cover.

A potentially significant impact that needs careful planning and controlling is that related to the possible increase in use of mangroves for recreation and tourism. Mangrove roots (pneumatophores) are sensitive to trampling, and the mangrove wildlife, particular breeding birds, are prone to disturbance. Tourists also often have a tendency to want to take souvenirs, such as leaves or seeds. This activity is unlikely to threaten the integrity of the mangroves, but should nevertheless be prevented.

Of the indirect impacts, the most damaging is the change in hydrological conditions. This was noted at several sites, for example, Sharm El Bahari and Marsa Shakraa where a coastal road has been built which affects the water flow to mangroves. At El Hamirah, a causeway/jetty has been built which may also be affecting the mangroves because of altered tidal flows and ponding effects (Photo 12). Combined with the impacts from intense camel browsing at this site, the mangroves here are highly stressed.

The most common indirect impact is perhaps solid waste and litter. This is not generally a major threat to the integrity of mangroves, but rather a major aesthetic impact, affecting people who may visit the mangroves. However, plastic bags and tin cans can interfere with mangrove growth (e.g. by smothering pneumatophores and leaves) and may release pollutants which could affect the health of mangroves.

Other potential impacts in the future include oil spills. Mangroves can be killed by heavy oil that covers the trees’ breathing pores and by the toxicity of substances in freshly spilt oil, which may impair the salt exclusion process. Sub-lethal effects also occur and may last for decades. This includes tree growth being suppressed and seed recruitment diminishing. However, oil clean up operations can also be highly damaging to mangroves, as can the use of chemical oil dispersants. There is evidence of historical oil pollution at some mangrove locations already (Dar, 2002). Research on Rhizophera stylosa and Avicennia marina in Australia has shown that severe mangrove deforestation from oil spills can take around 36 years to recover fully, with 50 percent recovery after 20 years (Duke et al, 1998). The sub-lethal impacts can occur for decades and be manifest in reduced forest canopies (20-30%) and partial loss of habitat, although effects on function and sustainability in the longer term are largely unknown. Impacts to older mangroves (some are estimated to be 150 years) are less easy to compensate for through restoration programmes.

Recommendations:

• Further investigations are needed into the threat of deterioration of mangroves at several sites caused by camel browsing and hydrological changes. Suitable mitigation measures and enhanced management measures should be considered and proposed to alleviate the problems.

8.2 Effect on socio-economic roles

The actual effect of mangrove impacts on socio-economic roles and economic values will be highly dependent upon numerous factors, many of them site-specific, such as:

• The nature of the impact;

• The consequences of the impact (e.g. stress, loss of leaves, branches, or whole trees);

• The extent of the impact (e.g. partial or complete);

• The main types of value at the site;

• The dependence of local communities on the mangroves;

• The natural rate of recovery, if any; and

• The ability to mitigate the damages and undertake mangrove restoration.

Some of the impacts would be immediate and direct, others may occur indirectly or gradually over time. The significance of losses would ideally need to be considered on a site-by-site basis. However, for damage assessment purposes, if considered appropriate, a standard fine could be developed, based on further analysis of the values discussed in this report.

The socio-economic impacts resulting from extensive damage to mangroves would be highly site specific, and would depend upon the existing relationships between local communities and the mangroves.

8.3 Benefits from mangrove management and restoration

Socio-economic roles and economic values of mangroves can be enhanced by mangrove management and restoration. Significant benefits can also be gained by altering negative environmental forces acting upon mangroves, a form of mangrove management. For example, as noted above, recent hydrological changes are causing stress to several mangrove sites in Egypt. If these stresses are not removed, then the mangroves may ultimately die off completely.

The economic and socio-economic impacts of mangrove management and mangrove restoration can be assessed using cost-benefit analysis (Spurgeon, 1998). This subject may deserve additional attention as part of the overall FAO mangrove management study. Individual cost-benefit analyses (CBA) could be undertaken to compare the overall long-term economic costs and benefits of alternative active management and restoration options. Future values can be translated into equivalent present day values, through use of a suitable discount rate. This approach can help justify additional expenditures for management, but it can also help identify the most economically viable and efficient options.

The main stages involved in the CBA process are to:

1) define the details for each feasible scheme (including the “with” and “without scheme” option);

2) determine the most appropriate spatial and temporal study limits;

3) identify all scheme costs and all scheme benefits;

3) place an economic (monetary) value, where possible, on all costs and benefits;

3) select an appropriate discount rate;

3) calculate “present day” costs and benefits through “discounting”; and

3) compare present day costs to present day benefits.

Those schemes with a benefit to cost ratio (BCR) greater than 1 are economically justified. Generally, the higher the BCR the more efficient the use of resources. The formula for calculating the BCR is:

T
Σ B_t / (1 + r)^t
_t=0


BCR = ------------------

T
Σ C_t / (1 + r)^t
_t=0

Where:

Σ = sum of values
B_t = benefit at time t
C_t = cost at time t
T = timescale of project
t=0 = start time of project
r = discount rate

The key marginal benefit that would accrue from mangrove restoration is likely to be:

• Fishery function = US$ 1.3/m²/yr.

Other possible marginal benefits, subject to the site, may include:

• Landscape value = US$ 10/m²/yr

• Coast protection = US$ 0.1/m²/yr

• Sediment regulation = US$ 0.1/m²/yr

Any increase in recreation and non-use value would depend on the extent of current mangrove area and the perceived difference the additional planting would make.