THERE is no denying the fact that Karachi’s green cover has reduced dramatically over the past few years with massive infrastructural development. Experts describe this situation as serious given the city’s vulnerabilities to the threat posed by climate change.

Faiza Ilyas spoke to Dr Zafar Iqbal Shams, a senior teacher at the Karachi University’s Institute of Environmental Studies, on how the recently launched tree plantation campaigns in the public and private sectors could be made successful.

With specialisation in ecology, Dr Shams was awarded the first doctorate degree in environmental studies in Pakistan. He is the author of a number of studies on the city’s flora.

Q: What species are best suited for Karachi?

A: No particular set of species is best suited to the entire city, because there is a variation in its topography that constitutes of terrain and soil profile. Some areas, specifically the coastal part of the city, are saline and waterlogged, for which coconut (Cocos nucifera) is the best tree. Cheekoo (Manilkara zapota), though exotic, does not generally disturb the ecosystem and is suitable for the coastal area. Moreover, mangrove species including conocarpus erectus thrive there since they are found naturally in the coastal belts of the world.

These species could also be planted in the city’s arid areas that receive continuous water due to leakages or seepage. They help improve the soil by reducing salinity and waterlogging.

However, the best species to plant in arid areas is date palm (khajoor), which does not generally disturb the groundwater table since its water requirement is rather low compared to species like neem, mango and cheekoo.

Last but not least, trees should be categorised on the basis of their size and must not be planted in areas where their shoots and roots can interrupt civic services such as overhead power lines, water and sewage lines.

Q: Are there any species which can help tackle rising temperatures and falling water table in the city?

A: The impact of rising temperatures could be reduced by covering concrete structures such as buildings, paved [paths], particularly black-top bitumen roads by a canopy of trees. Concrete structures, particularly of dark colour, such as black roads absorb heat and contribute to making weather hotter. Trees, however, work as a barrier between the sun and buildings.

Q: Do you think exotic species should be completely rejected?

A: Exotic species should not be absolutely rejected since they enrich the flora. But extreme care is required for planting exotic species since they are dangerous once they become invasive and start replacing local flora. For instance, Prosopis juliflora (keekar) and Leucaena leucocephala (ipil ipil) must not be planted since they replace the local flora and develop their own community.

Nonetheless, Guaiacum officinale (lignum) does not generally disturb the local ecosystem despite being an exotic species. Many other exotic fruit trees such as cheekoo and shareefa (sugar apple) are widely grown in Pakistan and India.

Australian eucalyptus can be planted in areas with a very high groundwater table since its water consumption is high. But its plantation in areas with low water table is harmful as the tree can affect the ecosystem of the area.

Q: How can the government ensure that saplings planted during campaigns are properly taken care of?

A: Generally, saplings of trees are secured by protective structures around them for a year or so. After that, there should be no need for their protection. The parks and horticulture department should be made responsible for taking care of trees.

Q: What are the species that the city has lost over time and are they still important?

A: The city has lost many native as well as exotic species. It needs diversity in flora and I would suggest plantation of Cordia gharaf (gondhni), Cordia myxa (lasura), Cordia macheodii (dhagan), Dalbergia sissoo (sheesham), Cassia fistula (amaltas), Crateva adansonii (barna), Erythrina suberosa (flame tree), Terminalia catappa (jangli badam), Delonix regia (large gulmohar), Ceiba pentandra (safed semal), Thespesia populnea (Indian tulip tree), Moringa oleifera (sohajna ki phali) and Aegle marmelos (bael).

Q: How can plantation campaigns be prioritised or can saplings be planted anywhere randomly?

A: Species like the conocarpus, neem, lignum, eucalyptus should be avoided since they are overrepresented in many areas of Karachi. Nonetheless, they must not be removed from the city’s landscape as they are currently providing ecosystem services to the inhabitants of the city.

The planting of saplings could be stratified, not random. Each of the 178 union councils of Karachi could be taken as a block for planting 20 to 25 different species of trees. The soil ecology of each town should be studied first for selecting 20 to 25 different species of trees since there is a variation in their soil type and soil profile. Different union councils may have different sets of species.

Published in Dawn, August 22nd, 2017