The mesquite Prosopis juliflora locally called valayati jand or Kabuli kiker is indigenous to the west tropical and sub-tropical North and South America (N.P. Mohan Punjab Forest Records 1940). It is well adapted in its native habitat to low rainfall and arid conditions. In Jamaica it is described as an admirable tree often attaining a height of 40 to 60 feet, growing in gravel soil and in situations where it does not rain for months. This species was introduced to Hawaii in 1828 and since then has spread from the seacoast up to an elevation of 2000 feet. It has also been successfully introduced in Australia and South Africa.
Available records show that the mesquite was introduced initially in the Indo-Pak subcontinent in Sindh to act as a sand binder in 1878. It has reproduced naturally over the Miani plain near Hyderabad through seed distribution by goats. It did well in Balochistan, the Pabbi Hills in the Punjab and near Peshawar in the early years of its introduction. In the canal irrigated areas the mesquite has assumed the role of an invader, particularly in the irrigated plantations of Punjab and Sindh. It grows naturally in the Pabbi hills, the Salt Range, the piedmont area, the mining wastes, plains, riverine forest area, waste agricultural lands, saline and waterlogged areas, the desert, the Sulaiman Range. It is found on almost all the linear land strips like highways, canals, and railway tracks. Sizeable areas of the Makran coast of Balochistan are home to the mesquite. The poor rural masses enjoy its free harvest for their domestic energy needs, is considered as a weed. The forestry departments spend huge amounts on mesquite eradication whenever new plantations are established.
Two species of mesquite (Prosopis juliflora and P. glandilosa), as well as five varieties were introduced in the country in the last century. These were the arid country form; the Mexican tree form introduced in 1912, the Australian form introduced in 1915, the Peruvian form introduced in 1915 and the Argentine form introduced in 1916. However, the majority of the varieties now encountered in the country are bushy forms. The PFI, Peshawar, has been successful in identifying and raising tree varieties of mesquite. This variety promises good quick green cover in the arid country.
Mesquite has occupied a niche by replacing the local flora. Some wildlife is known to prefer mesquite plantations for refuge. The unprecedented increase in the population of the wild boar after 1947 was partly attributed to the mesquite. Ecological studies on its effects on the local flora that it has replaced and its effects on the ecosystem have not been detailed, also research on its ecological and social impacts has not been conducted, yet there is a general view that it has helped the rural poor by providing a cheap source of fuel and livelihood for small traders in fuel wood and in charcoal kilns.
Invasive Paper Mulberry
Paper mulberry (Broussonetia papyfera) is a fast growing Southeast Asian species that has naturalised widely in the country. Records show that it was introduced in northern India (Saharanpur) in 1880. Parker in his Forest flora for the Punjab, 1915, feared it would become common in the sub-Himalayan tract and the irrigated plantations. He also reports its spread in Lahore and Shahdara Plantation in the first quarter of the twentieth century. Today it is one of the major weeds of all the irrigated plantations and neglected spots and is suppressing the growth of trees (Khan and Rizwanullah, 1981), even in areas not reported earlier (Khan and Adil, 1994). It was planted on a large scale in the new capital Islamabad in the sixties but today is a menace. Allergies and choking of sewerage lines in the urban set-up are attributed to the paper mulberry. The strategy of regeneration, both vegetative and by seeds plays an important role in its invasion. Birds disperse its fruit (which ripens in June). Additionally, it also sends root suckers, thus forming layers around the mother plant.
Other notable invasive species include:
Parthenium: (Parthenium hysterophorus) is a native of North Central America was probably introduced into the plains of Pakistan in late nineties through India where it was reported much earlier. The species has replaced the native vegetation and shows vigorous growth by forming thick continuous mats along the roadsides in many cities of the country where the climatic conditions are favourable. It is also one of the major weeds of the disturbed areas causing allergy.
Ailanthus: A native of China, ailanthus (Ailanthus altissima) was introduced in early 1970s. At present, it is growing along the roads and other naturally disturbed habitats of northern Pakistan. Ailanthus has already created a lot of problems in USA and Canada as invasive species because it produces abundant root sprouts that can develop into extensive thickets and displace native vegetation. In Pakistan, its impact as non-native species is yet to be evaluated.
Robinia: A native of North America Robinia (Robinia pseudoacacia) introduced in early 1990s in the hilly areas of northern Pakistan mainly along the road-sides and stream bottoms. It is feared by some experts that its rapidly growing stands may displace native vegetation particularly pine forests. Its assessment as an invasive tree is needed to be done at the earliest.
Lantana: One among the world’s worst 100 invasive weed, Lantana (Lantana camara) has extensively invaded the countryside by forming pure continuous thickets. It not only replaces the native vegetation but also repels the associated fauna by its strong odour. Lantana has entirely changed the vegetation picture of certain areas in Punjab and the Federal Capital.
Bagarius bagarius locally called Fauji Khagga is a kind of catfish, often called the ‘freshwater shark’ due to its voracious habits and ugly shape. It inhabits the freshwaters of South Asian countries like Pakistan, Nepal, India, Bangladesh, China, Thailand, Malaysia and Indonesia.
The records of Chashma Barrage landings and arrivals in the fish markets of the Punjab show that the population of this fish has increased significantly during 1990-1996. There is a general belief that this is an invasive species, and that it entered Pakistan’s rivers after the 1992 floods. However, this is not the case and it is only the sudden rise in its population. This could be due to some ecological disturbance. This sudden increase has made some naturalists think that it is an invader.
The catches from all the rivers, especially at the Chashma Barrage, contained very big fish ranging from 40 – 65 kg in weight. The autopsy of the fish stomach showed that each fish had preyed upon several dozens of fish of all kinds, inflicting heavy losses to other fish populations. During the years 1997-98 and 1998-99, the fish population of the Khagga was greatly reduced at Chashma due to the reduction in water supply and the draining of the water from the barrage reservoir for repair purposes. Hence, the reservoir became almost dry and consequently, the downstream area of the barrage became waterless. The fish moved further downstream and the catches at Chashma became negligible during the years 1997-98. The total weight of Fauji Khagga sold in the Lahore markets was 71 tons, which dropped to 9 tons in 1998-99 (Bhatti, 1999).