Just mention Islamabad and the image of a clean and green city with wide tree-lined roads appears in the mind. It is one of the few cities located adjacent to a national park and makes a worthy capital thanks to its scenic backdrop.

The master plan of Islamabad was prepared in 1960 by a Greek firm of architects led by the great Greek urban planner Constantinos Doxiadis, who is considered a pioneer in modern ecological urban design. Construction started in October 1961 and the city came to life in October 1966, when the first government office building in Islamabad was occupied. According to the master plan, one-fourth of the city’s land was reserved for green areas.

The native vegetation of Islamabad is sub-tropical evergreen scrub. Local plant species include wild olive (kahu), phulai, wild pomegranate (daruna), Chinese soapberry (reetha), katha, bamboo (baans), white mulberry (thooth), black mulberry (thooth siah) and banyan tree (bohar).

At the time it was declared as the federal capital, Islamabad was not as green as it is today. In a bid to rapidly increase the vegetative cover of the city, the Capital Development Authority (CDA) decided to introduce some fast growing plant species. The paper mulberry (jungli thooth), known for its scenic qualities and record growth, was imported from China during the 1960s. Alas, the species did what most alien species do when grown outside their native habitat: become invasive and grew at an alarming rate! It out-competed and replaced the local vegetation species and upset the natural ecosystem. The roots of this tree seek out moisture and so within a few years of being planted; it choked nullahs, broke sewage pipes and clogged water supply lines. Over the years, the alien invasive paper mulberry has spread to cities as far as Peshawar in the north and Sialkot in the south.

In addition to threatening natural vegetation, paper mulberry is a human health hazard. According to a report by the Pakistan Medical Research Council, about 45.5 per cent of allergy patients in Islamabad and Rawalpindi are allergic to pollen from this plant. Pollen counts as high as 50,000 per cubic metre have been recorded in Islamabad turning the city into the so-called ‘allergy capital’ of the world. Other allergy culprits in Islamabad include bottle brush callistemon sp, conocarpus and various grasses that release pollens particularly in the spring season.

Paper mulberry is an example of alien invasive plant species, but it’s only one of the plant varieties that have been brought to Pakistan either unintentionally, or imported for their beauty and economic value. These invasive species include exotic fruit trees, horticulture and floriculture plants. Avocado trees, some Chinese lemon varieties, herbaceous indoor plants as well as several types of flowering seasonal and perennial plants are rapidly gaining popularity in Islamabad.

According to one estimate, 1,400 alien species have been imported into the country in the last few years. Characterised by fast growth, rapid reproduction and the ability to tolerate a variety of environmental conditions, some of these species become invasive, outgrow local flora and compete for resources such as food, water and sunlight, thereby disturbing the natural ecosystem. Other alien species are poisonous or unpalatable, and although may not be invasive, contain toxic chemicals that can be dangerous, if ingested by animals or humans.

Common alien invasive species of Margallah hills include the lantana, common cocklebur, carrot grass, castor oil plant, mesquite, marijuana and paper mulberry.

According to Dr Ghulam Akbar, Director Worldwide Fund for Nature (WWF-P) Islamabad, there are some essential steps that should be taken to preserve the local flora and discourage the import of alien invasive plants. “The most important thing is to enforce the quarantine laws for plants whereby the plants and seeds brought into the country are strictly regulated,” explained Dr Akbar. “We also need to conduct more research on the impact of these alien species on the local flora and fauna as well as raise awareness among the local communities regarding the importance of preserving native ecosystems,” he added.

The CDA, having made incorrect decisions earlier, is now trying to rid Islamabad of this menace, and is involved with various NGOs in cutting and removing these alien invasive plants. Tighter control at ports of entry will also ensure that these species are prevented from entering the country.