Impact
Swamp Development has a considerable impact on environment. The most important is the disappearance of the natural vegetation and its flora and fauna which is unique and in great danger to disappear completely for large areas in Indonesia.
However the way to protect the environment is still a subject of controversy. Most of the Swamp forests will be lost in the near future. This already happened for large areas on Sumatra and Borneo (Kalimantan). This development wil not be stopped. For that reason it would be now more than ever of great importancy to protect the National Parks in the swamp areas of Indonesia. The most difficult task will be to avoid illegal logging. That requires constant monitoring and the assistance of the local government.
Beside the loss of an unique flora and fauna there are other negative impacts. Some impacts of development are important but some of them are less important than often claimed. I will explain:
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The sponge working of swamps during high rainfall is not valid for peat soil domes; domes are characteristic for peat swamps in Indonesia. There is no extra storage possible in the already saturated peat soil and water will disappear directly to the adjoining lower lying areas, mainly by interflow (sub-surface flow on a slope). As a prove I can show you developed tidal lowland areas bordering peat soil domes that could suffer severe deep flooding during high rainfall when there is no interception drain and dike bordering the peat soil dome. There are publications like: Indonesia United Nations Assessment and Coordination Team Mission on Forest Fires, that says that during high rainfall the peat works like a sponge: wrong thus! Peat domes work only as a sponge during dry periods when it still releases water to lower lying areas. (correctly, luckily, also mentioned in this paper of the Mission). For more information on peat domes see webpage: Thesis: peat soils and acid sulphate soils |
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In the flat low lying areas of the Tidal Lowlands (usually not peat soil, but clay soils) there is surface water storage possible from mainly local rainfall during high rainfall periods. When these areas are developed and used for wetland rice this storage is still available and probably has even a bigger storage than before development, including the canals. With the intensive canal system tidal flooding is possible over a much and much larger areas than before the development in undisturbed swamp forests and these extra tidal flooded areas in developed Tidal Lowlands will reduce the flooding problem from the river elsewhere. |
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When the Tidal Lowlands are developed for housing and industry, like in Palembang city, then a flooding problem is also highly likely because all local flooding storage potential has disappeared. Still even in this case the Tidal Lowlands have much better potentials for drainage than the areas more upstream, in the river flooding areas. Gravity drainage for Tidal Lowlands is still possible during low tide, but only when the proper drainage system is installed that is needed for the urbanization. |
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Upstream changes on landuse usually have only a minor influence on river flows in Tidal Lowlands, a great advantage for the Tidal Lowlands in comparison with the river flooded areas more upstream! However more flooding might occur in areas on the border of the Tidal Lowlands upstream. |
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A negative impact often
mentioned, when wetlands are lost, is the effect on climate
it could have. Wetlands would work as sponge and will release evaporation
over a long period of the year. That will be surely valid for more dry
climates, but for the tropical rainforest climate of Indonesia that effect
would be less important. When two wetland rice crops are grown per year in
the Swamp Schemes, there would be even no significant difference with the
original conditions in respect to evaporation.
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When tree crops are grown,
high excess rainfall will be released within a few days to the river. For rice crops this
release will be much slower. In the Tidal stretches of the river this impact will be small
in comparison to areas more upstream with river flooding,
where it could be important.
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The sponge working of the Tidal Swamps in natural conditions has
only a local effect on the soils (for instance on how often and how deep the groundwater
will drop during the dry season) but in natural conditions there is no gradual release of
water to rivers because the area is completely flat. (This applies to mineral soils, not
to peat domes)
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The sponge working on the edge of peat domes could be important for the lands bordering these peat domes, mainly important for dry periods. These lands will receive water from the peat domes by surface flow for a long period of the year. Reclaiming peat domes for development should take in consideration a sustainable flow to the adjoining lands near the river. |
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The river borders are a very important part for of the natural Tidal
Swamps which should be preserved as much as possible. At other places wildlife should have
access to river borders through corridors.
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An important negative
effect of agricultural development is the deeper and longer exposure of the pyrite layers in the subsoil
after the land has been reclaimed and an increased release of acids to the adjoining
canals.
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In natural conditions the groundwater level will also drop below the pyrite layer in acid sulphate soils during a long dry season, but not as frequently as in areas developed for agriculture. The reason is that under natural conditions the soil is often inundated at the end of a wet season, after which it takes a long time before the water layer will evaporate and the groundwater drops below the pyrite layer. It might be clear that in developed areas for agriculture such a deep continuous flooding can never be allowed and therefor pyrite will be exposed more often than under natural conditions. Frequent exposure of pyrite applies to conditions when only one rice crop is grown per year, or tree crops are cultivated. After a number of years a new balance will be found between drop of groundwater level and acidity release when sufficient leaching will be applied and the pyrite layer will drop to lower levels in the deep subsoil.
Acid pollution within a Scheme.The increased pyrite exposure after reclamation will release large quantities of acids to the direct environment at the beginning of the wet season, mainly in the adjoining canals. This leaching is essential to maintain healthy growth of rice plants. Farmers should be encouraged to improve the leaching conditions at field level. See Thesis. However the acidity release will have a negative effect on fisheries and domestic water uses. Water quality management in the canals is still an aspect of the infra-structure development which is under-valued in importance. Much more could be done here by better water management and improving the flushing capacity of the canals by promoting one-way-flow in the canals based on gate operation within the system. An important way to tackle the acidity problem is also the introduction of double connected canals. The main problem is found deep inside the Schemes far away from the rivers where slackwater conditions prevail.
Examples of acidity problems and effects of stagnant groundwater in the root-zone of the rice-plant.
Acid release to surrounding environment. In Swamp development often the acidity release to the environment is mentioned. See also an Australian Website that warns against the construction of floodgates in the Vietnam Mekong Delta.
My comment: As mentioned above, the proper water management within a scheme is extremely important. However the effect of the water management on the environment, surrounding the scheme, is in all cases very limited. The buffer working of the adjoining water courses is apparently enormous in comparison with small amounts of acids and other toxic components which are released daily to the surrounding environment. Years of monitoring in Indonesia proved that no significant pollution can be found at the borders of the schemes near the rivers and natural tidal water courses. Based on the data I have seen in Vietnam during a Consultans Mission to that country, also in Vietnam in the Mekong Delta, before and after the gates have been constructed, the acidity release from the Rice growing Schemes to the surrounding estuaries and tidal environment can not be measured at the borders of the Schemes. But problems are reported for fish-and shrimp ponds in the mangrove areas. Here the sudden release of large quantities of acids from bunds and dikes during and directly after construction may damage the direct environment of the mangroves.
Practically experience and Computer Modelling (Duflow and SMASS) shows that the best strategy in Indonesia and Vietnam will be leaching from the soil and flushing in the canals, by one-way flow in the canals, during the first rains after the dry season.
Pollution from agricultural chemicals. Farmers apply little land preparation and weeding and prefer direct planting of the seedlings in plant holes (TOT). The presence of acids causes usually low yields. Farmers do not have a tertiary field drain system (Micro-system) By the absence of a Micro system there is little drainage- and flushing-potential to remove the acids. Because of the acidity problems the rice plants are weak and susceptible to diseases and pests. The absence of good weed control contributes to rat problem in tidal lands. The wide spread of the planting season by the lack of manual labour even more contributes to the rat problem.This all increases the need for herbicides and pesticides with as a result a strongly polluting effect on the environment. See under web page Thesis, need for mechanisation, how this problem can be minimised.
Sea-level rise by greenhouse effect: The possible sea-level rise in the coming hundred years will have relatively little effect in the swamps of Indonesia as long the rise is not more than a few decimeter. (say less than 50 cm). The positive effect will be that the tidal irrigation potential will increase. The negative effect of an increased need for flood protection in low lying areas will be limited and will not require large inputs. Most of the developed tidal swamp land is situated above mean high water level, so dikes will be relatively low.
The statement on the web about Indonesia: vulnerability to climatic change and adaptation that 20 % of the tidal rice and other swamp uses will be lost by a sealevel rice of 60 cm is questionable. ( I have also a feeling that the report on the web mixes coastal land subsidence by intensive urbanization, with possible sealevel rise)
The main worry is for the areas with a small tidal range, like in West Kalimantan, where the drainage potential may become very small, especially peatlands (not used for tidal rice) are in danger. However the vast majority of the developed rice land in the swamps of Indonesia has tidal ranges of more than 2 meter. These areas will maintain sufficient drainage potential after a sea-level rise.
There is also an unexpected positive impact of swamp development:
Swamp Schemes could be important for fisheries and waterbird life. In places with good water quality lots of fish can be found everywhere and during high rainfall periods also in the fields. Large groups of waterbirds can been seen in many places. The access from the river to land and food through the many canals will provide for the fish even a much larger habitat than in the original natural swamp land conditions. Original Swamp Land in Indonesia under natural conditions has not a significant fish and waterbird life at places away from the river. It is therefore important that Swamp Scheme Developers will be aware of this new fish and waterbird life and will take into consideration how to manage the Schemes such that these resources will not be lost.
The destruction of the Forest in the Forestry Concessions of South Sumatra province.
Swamps need Management and Technology Development to protect them. See what happens when you ignore or oppose!
Two thumbnails of Landsat TM images (Left 26 June 1992, Right 7 May 2000, each covering about 30,000 km2, showing major parts of the Musi River Basin).The dark green colours on the left image are mainly the forestry concessions in the Swamps of South Sumatra. On the right image you can see the forest has gone almost completely. What remains is only secondary low bush land. On the left image I have drawn the deep peat areas with a black line, the Swamp Schemes encircled with a red line and the border between swamp and upland has a purple line. Swamp Schemes are Government sponsored and spontaneous local development. Note that 1992 was a very dry year; the red/purple colours are mainly burnt bush and degraded forest land.
That the forest has gone in these years is not the result of Swamp Scheme development, but the result of uncontrolled wood cutting and wrongly managed forests by big Concession Holders. The Swamps as a whole have been neglected too long, because of lack of clear management policies for them. The Environmentalists have been trying too long to stop the use of swamps in all aspects. The Developers ignored too long what was happening in the forested Peat Swamps. Better find strategies to manage the swamps as a whole, including the forested peat lands, the degraded peat lands and the Swamp Schemes. They do!
More information about the Musi River Basin and its catchment areas for comparison, see webpage Potentials.
Some people believe in certification to protect the natural environment such as in Berbak National Park and its buffer zone. (Certification means you pay the stakeholders when they protect the Natural Environment). May be that might help, but first of all, I believe, we need a technology in the degraded forests and bush lands in the swamps that is sustainable and profitable such that nobody will be interested in the wood of the protected forest areas. Otherwise the wood of the Natural Forest will remain an attractive income. The combination of certification and new economic forestry technologies might strengthen the effort to protect the original natural forest in peat swamp areas.
On the Webpage Problems I explain the main problems in peat soil: hydrophobic peat and subsidence of peat soil below sealevel. The problem of hydrophobic peat soil is solved by planting tree crops instead of annual cropping. However the problem of subsidence is not solved. Oilpalm needs for instance a watertable at 60-80 cm below surface for good production. That means a subsidence of 8-10 cm per year for deep peat! With as a consequence many oilpalm plantations will be not drainable after 20-30 years and the land will become useless, putting an extra strain on the remaining protected natural forests! On Webpage Problems I provide a suggestion in which direction research should go in my opinion to sustain the use of peat lands.
Also some information about the problems with peat soils is found on webpage Thesis
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