A species if it has been introduced by man to a location, area or region where it did not previously occur naturally Ballast water Cargo ships normally use seawater to provide ballast. At source port it fills in the seawater while discharging the cargo. At the destination port it discharges the ballast water. There are thousands of marine species that may be carried in ships’ ballast water. This may include anything that is small enough to pass through a ship’s ballast water intake ports and pumps. These organisms include bacteria and other microbes, small invertebrates and the eggs, cysts and larvae of various species. The problem is compounded by the fact that virtually all marine species have life cycles that include a planktonic stage or stages. It is fortunate that a vast majority of marine species carried in ballast water do not survive the journey, as the ballasting and de-ballasting cycle and the environment inside ballast tanks can be quite hostile to organism’s survival. Even for those that do survive a voyage and are discharged, the chances of surviving in the new environmental conditions are generally low, particularly where predation by and/or competition from native species further reduces the chances of survival. However, when all factors are favourable, an introduced species may survive to establish a reproductive population in the host environment, it may even become invasive, out-competing native species and multiplying into pest proportions. As a result, this factor imposes problems on the whole ecosystems and the community composition begins to change. It is estimated that at least 7,000 different species are being carried in ships’ ballast tanks around the world.
Pakistan needs to start a program to monitor ballast water for possible invasive species. The Karachi Port Trust (KPT) authority Karachi has started such a program and efforts are planned to meet the international obligations in this regard. Ports in Pakistan should have proper receptacles for collecting ballast water as required under "Guidelines for the control and management of ships’ ballast water, to minimize the transfer of harmful aquatic organisms and pathogens". These Guidelines were adopted by the IMO Assembly in 1997, by resolution A.868 (20) of the GEF/UNDP/IMO ‘Global Ballast Water Management Programme (GloBallast)’.
It has been reported by the KPT that among flora, the dinoflagellates, diatoms and algal spores of the blue green algae may be transported through the Ballast water. Among fauna, the planktonic life forms of crustaceans copepods, barnacles crabs etc have the tendency to be transferred from one place to another. According to some studies, ctenophores and cnidarians are more opportunistic to transfer from one place to another place through ballast water. KPT has requested the Ministry of Science and Technology through Ministry of Ports and Shipping to participate in this program
There is virtually no awareness on this important issue among general public and policy makers, therefore awareness on the dangers and adverse impacts of alien species is required to be created.
The Biodiversity Action Plan (BAP) of Pakistan deals with alien species problem very superficially. The action 6.6 of BAP reads as; “Take measures to control invasive alien species of fauna and flora, and to prevent further introduction”. To achieve Millennium Development Goals (MDGs), Pakistan has made some headway regarding environmental sustainability and reducing environmental degradation by promoting indigenous species.
Since Pakistan is signatory of CBD and other Multilateral Environmental Agreements, these agreements obliges countries to undertake necessary control measures to prevent the spread of invasive alien species, pests and diseases. Well-established quarantine facilities are required to be developed to cope with the danger of invasive invasion
Freshwater Alien Invasive Species
Pakistan is blessed with about 225 significant man-made and natural wetlands spread over approximately 10% of the country. Pakistan’s wetlands occur in a broad variety of ecological zones including arid, semiarid, alpine and coastal areas. The problem of invasive species, though not sufficiently quantified, is increasingly being recognised by scientists for their impact on biodiversity. There is, however, limited awareness of the problem in general and lack of capacity to address the issue in Asia, including Pakistan (Hussain et al, 2000).
Unfortunately, several of the freshwater bodies in Pakistan are badly affected by invasion of some alien invasive species like Water fern (Silvinia molesta), water hyacinth (Eichhornia .crassipes) and water lettuce (Pistia stratiotes). The issue of alien invasive species is relatively new in Pakistan and any comprehensive cataloguing of alien species or any study on the magnitude or impacts of invasive species has not been done so far. For the very first time in year 2000, CABI SA and IUCN-Pakistan conducted a workshop and compiled a joint report in which several invasive species have been black listed including aquatic plants like Silvinia molesta, Eichhornia crassipes and Pistia stratiotes. These invasive species have been accidentally introduced in the wetlands of Pakistan. Among these, water fern (S. molesta) is the most aggressive and dreaded aquatic weed, which has established itself in many tropical countries, like Sri Lanka, India, Zambia, Australia and South Pacific islands. The plant is native to southeast Brazil (South America) and introduced in Pakistan through an unknown source. Now, it has spread to many wetlands of Sindh and few lakes in Punjab. The exact distribution of S. molesta in Pakistan is, however, not known and needs to be explored. It is reported that Salvinia is carpeting some lakes of international importance like Kinjhar Lake, Haleji Lake and various irrigation canals and ditches in the Thatta District of Sindh Province.
Similarly Eichhornia crassipes, native of Amazon basin, South America was first brought outside its native home as an ornamental plant, but it became an aggressive invader in all tropical and subtropical countries. Exact time of arrival in Pakistan is not known. This species is widely distributed in water bodies of most parts of Pakistan, except in the high altitude and cold regions. It is a highly invasive species due to extremely fast growth rate and gregarious nature. Like in many other tropical countries, it is becoming a troublesome invasive in Pakistan also.
Pistia stratiotes native of South America is widely distributed in Pakistan and found in water reservoirs, ponds and marshes along the edges of large lakes where they are able to thrive amidst the offshore vegetation and debris, in slow moving or stagnant waters and in old wells.
In developing countries like Pakistan, the impacts of alien weeds can be devastating. The major impacts reported by many scientists are:
Socioeconomic damage: Mats of S. molesta, E .crassipes and P. stratiotes impede access to and use of waterways for commercial and recreational purposes and degrade waterside aesthetics. Mats reduce habitats for game birds, limit access to fishing areas, and probably alter fisheries, all with negative economic consequences. Invasive alien aquatic weeds can clog water intakes and interfere with agricultural irrigation, water supply, and electrical generation. Weed mats provide excellent habitat for mosquitoes (important vectors of human diseases) with serious socio-economic impacts.
The impacts can be devastating because weed mats block the use of waterways for transportation, cutting off access to important services, farmlands, and hunting grounds. The harm from weed mats to fisheries also can be very significant to communities dependent on fish for local consumption (sometimes as the main source of protein) or in areas where fish sale is the main source of cash income (Bennett, 1966; Thomas and Room, 1986). Salvinia is also a weed of paddy rice that reduces production by competing for water, nutrients and space.
Ecological damage: The ability to grow very quickly (Cary and Weerts, 1983; Mitchell and Tur, 1975; Mitchell, 1978/9; Room, 1986) and blanket water bodies makes salvinia an aggressive and competitive weed. Initially, salvinia forms a single layer over water, but with continued growth the mats become multi-layered and can reach up to 1m in thickness (Thomas and Room, 1986). Thick mats support other colonizing plants, and the high biomass and stability of such mats make them difficult to dislodge and destroy (Storrs and Julien, 1996).
Plants and animals dependent on open water to gain sunlight, oxygen, and space for sustenance and growth, or for landing, fishing, nest building, or mating, are displaced by dense weeds infestations. Water under mats of aquatic weeds has a lower oxygen concentration (due to reduced surface area of water available for oxygenation, inhibition of photosynthesis by submerged plants, and consumption of dissolved oxygen by decaying Salvinia), higher carbon dioxide and hydrogen sulphide concentrations, lower pH, and higher temperatures than nearby open water (Mitchell, 1978; Thomas and Room, 1986). Through high growth rates and slow decomposition rates, salvinia reduces the concentration of nutrients that would otherwise be available to primary producers and organisms that depend on them (Sharma and Goel, 1986; Storrs and Julien, 1996). Animal habitat is most noticeably altered by the obliteration of open water. Migratory birds may not recognize or stop at water bodies covered with these weeds, which may alter the route and can cause change in the natural ecosystem.
Biological control of water weeds
Water weeds have become a menace in the provinces of Sindh and Punjab; weeds not only reduce the efficiency of the irrigation system but also badly affect the freshwater ecosystems. This infestation causes depletion of fishes and also destroys the feeding grounds of water birds. Heavy investments are made to remove weeds from the Lal Sohanra National Park Lake each year with little success. The Commonwealth Agriculture Bureau CABI has the technology and expertise to control the water weeds through cheap biological control methods. According to CABI biological control through the introduction of natural enemies of Salvinia molesta, Eichhornia crassipes, water Hyacinth etc. has been tested in other countries by the controlled release of weevils. The weevils have not shown any negative impact on the environment as shown in the tables below:
Table 15.2: Status of Releases of Cyrtobagous salviniae Calder and Sands
Initial Release Date
Control in tropical and subtropical areas; some control in temperate areas