Adverse Environmental Effects of Seismic Surveys: Virunga Hippos, Fisheries…Illegal

For offshore exploration, the oil and gas industry typically relies on arrays of airguns, which are towed behind ships and release intense impulses of compressed air into the water about once every 10 to 12 seconds. Although most of the energy from these acoustic “shots” is intended to search downward for evidence of oil and gas deep beneath the seafloor, a significant amount of the energy travels outwards and can be heard throughout vast areas of the ocean.


The environmental problems created by these noise invasions are not fully understood, but we do know that these intense sounds threaten the habitats of endangered whales and commercial fisheries, and cannot remotely be confined to the waters off individual states that approve offshore production. Seismic surveys have been shown to disrupt essential behavior in endangered whales and cause catch rates of some commercial fish to plummet—in some cases over enormous areas of ocean. (Source: NRDC)

Considering the impacts of seismic surveys in oceans, what would be the effects of SOCO’s seismic surveys in Lake Edward, a fragile, closed water system with a recovering hippopotamus population? In 2010, WCS estimated that the number of hippos in Virunga National Park was about 1,000 individuals.

Here below some adverse effects of seismic surveys……

Impact on Fish

The powerful sound wave generated by seismic survey can have a variety of harmful effects on fish. Within close range, seismic survey has been found to kill adult fish as well as larvae and fish egg. Scientific study have also shown that air gun blast can cause a variety of sublethal impact on fish such as damaging orientation system and reducing their ability to find food. Researchers have noted disturbances in the migration routes of salmon and other anadromous species as a result of seismic operation [14,15]. Seismic survey can cause physical damage to fish ears and other tissues and organs such as swimming bladders. Although such effect may not kill fish immediately, they may lead to reduced fitness, which increase their susceptibility to predation and decrease their ability to carry out important processes. If a natural gas blow out occurs, marine fish, eggs and larvae near the blow out point probably would be killed.

Natural gas condensates in the water column would be hazardous to any fish, eggs, or larvae that were exposed to high concentration. There are at least five possible ways (oil spills) can affect fish pollution: (1) eggs larvae can die in spawning or nursery areas due to coating or direct toxic effects (c) adult can die or fail to reach spawning grounds; (3) spawning behavior may be changed; (4) local food species of the fish or larvae may be adversely affected or eliminated; and (5) sub-lethal effects may reduce fitness and affect the ability to endure environmental stress Seismic surveys not only threaten commercial and subsistence fishing by harming fish resources, but also by interfering with fishing operations and dramatically affecting catch rates. Studies have shown that seismic operations have greatly reduced catches of fish around areas where air guns were being fired. This studies have demonstrated reduced catches over 20 miles away from the source with catch reductions continuing five days after the testing was complete.(See Table 1 below).

Impact on Birds

About 100 species of waterfowl, shorebird and seabirds occur in the coastal waters or the Niger Delta [4]. Sitting of onshore facility such as drill pad, road, and oil storage facility could eliminate or alter some preferred bird’s habitat such as wetland. The construction of offshore pipeline could have temporary effects on the availability of food sources of some sea ducks with a mile or two of the construction area due to turbidity and removal of prey organisms along the pipeline route [9]. Noise and disturbance may affect marine and coastal birds. Repeated air-traffic disturbance of concentration of feeding and molting water fowl and shorebirds on coastal lagoons and other wetland may reduce the ability of migratory birds to acquire the energy for successful for migration [9]. In the event of natural gas exploration and fire, bird in the immediate vicinity would be killed. It is not likely that toxic fumes would affect birds or their food source except those very near to the source of the blowout.

Direct oil contact alone usually is fatal and often results in substantial mortality of many birds. Oiling of birds causes death from hypothermia, shock, or drowning. The direct effect of oil on a bird is to clog the fine structure of its feathers, which is responsible for maintaining water – repellence and heat insulation. (NRC 1985). Hundreds of thousands of marine birds are estimated to have died as a result of contact with oil spill from the Exxon Valdz [10].

Impact on Marine Mammals

The sounds generated by seismic surveys are colossal peaking momentarily at up to 259dB at source. Moreover, they are repeated approximately every 10 seconds for weeks or months at a time. Not surprisingly, marine mammals have been recorded as fleeing from seismic survey sites.

Habitat loss would be limited to temporary disturbance to some sea otters and harbor seals in the near shore environment associated with construction of pipelines and transport facilities.

Noise and disturbance activities that may affect marine mammals in the sale area includes geophysical survey, marine dredging and construction, support vessels, aircraft over flight, offshore drilling and production. If a natural gas blowout occurred with possible explosion and fire, marine mammals in the immediate vicinity of the blowout could be killed. Natural gas and gas condensates that did not burn in the blowout could be hazardous to marine mammals. Spilled oil can affect mammals through direct contact with the skin surface, inhalation of petroleum hydrocarbon, vapors, injection or through interference with normal behavior. Laboratory studies on phocid seals have also demonstrated that petroleum hydrocarbon may be transported by the blood and distributed to many tissue including blubber, muscle and liver [11].

Impact on water quality

For offshore operation, non hazardous waste that cannot be returned to the surface is treated and discharged. Drilling method for onshore and offshore wells are similar but disposal of by products varies. For onshore operations, most drilling waste are disposed of under ADEC’s solid waste disposal program, or shipped out of state, byproduct or drilling and production activities include muds and cutting, produced water and associated waste (non hazardous) and some times oil spills that might contaminate and pollute the water.

Impact on land habitat

Effects of constructing production pads, roads, and pipelines include direct loss of acreage due to gravel infilling, and due to impediment and diversion of water. A secondary effect of construction activities includes dust deposition, which may reduce photosynthesis and plant growth, and downstream saltation and sedimentation, which can affect plant viability. If natural gas blowouts occur, plants in the immediate vicinity may be destroyed. Spilled oil affects vegetation depending on time of the year, type of vegetation and terrain. Spilled oil will migrate both horizontally and vertically. This flow depends on factors including the volume spilled, type of cover (plant or snow), slope, presence of cracks or troughs, moisture content of soil, temperature, wind direction and velocity, thickness of the oil, discharge point, and the ability of the ground to absorb the oil [12. If the oil penetrates the soil layer and remains in the plant root zone, longer-term effect, such as mortality or reduced regeneration would occur.

Impact on marine animals

Scientific studies have established that some man-made sounds can injure some marine animals, disrupt or mask crucial sound on which they depend and also cause behavioral changes. Louder “acoustic harnessing device” (AHD) can create a problem of habitation. Prolonged exposure to AHDs that emit up to 200DBof sound in the 5-30khz range (AHD)cause hearing loss in the animals ranging from temporal threshold shift to permanent threshold shift and an increase in pathological stress.

As a result the animals are more likely to be separated from their young, who in turn, will become easier prey for natural predators. That intense noise exposure may cause death or physical injury, even at low levels for some vulnerable species (including, temporary or permanent hearing) as well as increased leading to detrimental consequences for animals immune system and reproductive health.

Impacts on man

Gas flares have potentially harmful effects on the health and livelihood of the communities in their vicinity, as they release variety of poisonous chemicals including nitrogen dioxide, sulphur dioxide, benzene, carcinogens like benzapyrene and dioxine. Human exposed to such substances can suffer from a variety of respiratory problems. These chemicals can aggravate asthma as well as cause leukemia and blood-related diseases. Many of these communities claim that the nearly flares cause acid rain which corrodes their homes and other local structures, many of which have zinc-barred roofing.

People living in the oil spill affected areas complain about health issues including bathing problem and skin lesions, many have lost basic human right such as health, access to food, clean water and an ability to work. Generally, seismic activities lead to;

  • Depletion of arable farm land destroys economic and crops, thus reduces farmer’s access to land/food.
  • The action has rendered the areas inhabitable and lead to the exodus of man and animals.
  • Oil spill and drilling wade contaminate source of drinking water.
  • Network of pipe connections, well heads and floor stations restricts the activities of the dwellers.
  • Kill fish which is a source of protein and deny the fishermen from fishing as a means of livelihood.