This section describes Pakistan’s main ecological zones, habitat types, and plant species of particular importance. The major threats to Pakistan’s plant Biodiversity and these habitats are listed. Actions that have been taken or are proposed for plant Biodiversity conservation are described.
Pakistan is situated at the western end of the South Asian subcontinent. Its flora and fauna have the characteristics of both Palaearctic and Indo-Malayan elements. Climatically, Pakistan is largely arid and semi-arid. However, there are wide geographic, altitudinal, and physiographic variations, from the tropical coast in the south to the high mountains in the north, with altitudinal variation from sea level to about 8000 meters. Annual rainfall ranges from less than 50 mm in arid and semi-arid areas to 2000 mm in moist areas of the Himalayas. The temperature (influenced by the altitude) ranges from below freezing levels in the northern mountains during winter months, to 35-50oC during the summer in the central plains. Based on these variations across the country, a number of distinct ecological zones and habitat types have been classified, although not according to any recognised system of classification. In this regard, Roberts (1977) divided the whole country into 9 major zones, covering eighteen habitat types.
Pakistan is a land of some of the oldest civilisations in the world. Its Practices in the use of natural resources are thousands of years old. Natural habitats have been widely modified by human activities and very few natural forests remain unaltered. The degradation and loss of natural habitats has occurred for thousands of years, but the process has been accelerated in the last few decades due to rapid development activities and population expansion. Recently, with the development of the canal system, an extensive area in the Indus plains has come under the cultivation of agricultural crops after the clearing of forests (including the riverine forests of Punjab and Sindh).
Despite the large-scale modification of natural habitats, many Biodiversity-rich ecosystems are still found. These are described in the following sections.
2.1.1 Balochistan Juniper Forests
Balochistan’s forests are one of the most extensive and oldest juniper ecosystems of the world. These provide habitats to many unique birds, mammals and species of plants that have a very restricted range of distribution. This extensive open woodland is spread between 2100-3000m. At higher elevations the trees have become stunted and dwarfed and form large prostrate patches on rocks, especially on wind exposed slopes in the Ziarat, Zarghun and Harboi Ranges. Generally, above 2800m juniper trees become more sparse and are gradually replaced by curious hedgehog-like dwarf shrubs.
The main species-Juniperus excela subspecies polycarpos, is a very slow-growing species. Some trees are thousands of years old and suffer from ageing, parasite disease, and impacts of climate change, heavy grazing and deforestation. Several species found in the juniper tract are endemic to Balochistan or extend their distribution to neighbouring areas of Afghanistan and Iran. The species’ restricted range of distribution increases the importance of this ecosystem, making these mountains centres of endemism in the region. Some of these endemic species associated with juniper forests include Berchemia pakistanica, Amygdalus brahuica, Cotoneaster afghanica, Cotoneaster rechingeri, Cerasus rechingeri, Spirea brahuica, Aitchisonia rosea, Gaillonia afghanica, G. macrantha, etc.
Juniper forests include some of the oldest trees of the country. Unfortunately, this national heritage is facing threat from a parasitic disease caused by a small plant - the dwarf mistletoe (Arceuthobium oxycederii). This parasite is expanding in the Ziarat juniper tract and it needs immediate attention to protect the ecosystem, which is providing habitat to several endemic species of shrubs and herbs in the forest under growth. Box 1 gives an account of the status of conservation of the juniper forests.
Box 1: The Juniper Forests of Balochistan2
The juniper forests of Balochistan are among the few representative examples of this species in the world. These forests grow on calcareous soil between 2500 and 3000m in dry cold climates with only 200-300mm rainfall per annum. This makes it a unique ecosystem. Juniper is an extremely slow-growing species and attains only one-inch diameter growth and one cft in 50 years. Ziarat, Zarghoon and Harboi are the best examples of pure juniper stands in Balochistan. The scarcity of water in and around the juniper tract has increased the importance of this species, as it plays a significant role in protecting the land from wind and water erosion. The Biodiversity Action Plan (BAP) of Pakistan describes this important ecosystem as critically threatened and strongly recommends immediate measures to protect and conserve this natural heritage. Overexploitation, changes in land use practices, disease attacks and low germination rates are a few of the major threats to this important species. In Zarghoon Valley alone, 3900 kg of juniper wood is cut down annually for domestic use. The lack of substitute fuel wood or other energy resources is a very big threat to the existence of these forests. If the existing growth rate of the population and juniper forests is assumed mutually compensatory, then the existing reserve stock will suffice for only a few more decades. The dwarf mistletoe (Arceuthobium oxycedri) is a serious parasite that is carried and spread via birds, the mistle thrush, and wind. This parasite badly effects the host tree (juniper), resulting in the trees drying, poor growth and retarded seed development. The Pakistan Forest Institute, Peshawar, and the Forest Department of Balochistan to overcome this problem have undertaken a number of efforts. Due to their landscape, physical structure, geological formations, petrified forests and natural water sources, juniper forests have great a potential to attract tourists in other areas besides Ziarat. Properly managed ecotourism in these ecosystems can be an effective means to educate and create awareness among the public and tourists about the importance of this unique species. It can also generate income for the locals, which will ultimately reduce the pressure on these natural resources. The Forest Department is executing an extensive project under the Balochistan Natural Resource Management Project (BNRMP) for the improvement of this unique ecosystem. WWF-Pakistan is also working with the custodian communities to protect this natural heritage. The first phase of this project has been successfully completed in Rodmalazai juniper tract. The second phase is under implementation in the Ziarat juniper ecosystem.
2.1.2 Chilghoza Forests
Chilghoza pine (Pinus gerardiana) form forests in the dry northern mountains of the country. It is not widespread. Large-scale deforestation of these forests has already occurred in certain parts of the Northern Areas.
The Chilghoza pines of the Sulaiman range of Balochistan form a unique ecosystem, providing a habitat to endemic mammals like the Sulaiman Markhor, as well as endemic species of plants. On higher elevations, Juniperus excelsa subspecies polycarpos is the other associated species.
2.1.3 Balochistan Subtropical Forests
Most of the land of Balochistan is arid and does not support the growth of large forests. Subtropical broadleaf forests mainly composed of wild pistachio and ash species have very small and scattered populations. Wild pistachio trees (Pistacia atlantica subspecies cabulica and Pistacia khinjuk), a more commonly grown species, is scattered at intervals on lower slopes of hills or along dry watercourses. In some places, it grows gregariously with wild ash (Fraxinus xanthoxyloides) forming small patches with open forest in dry watercourses. These receive water during the rainy season. Such examples can be seen near Quetta in Hazarganji-Chiltan National Park and near Zhob. They never form close canopy forests and the under growth is similar to surrounding areas without trees.
In Balochistan, this forest type appears to have been greatly affected by man and his domestic livestock. These open woodlands are located in the northern part of this province, which experiences extremely cold temperatures in winter. Located at the valley bottom, it is easily approachable and subjected to loping for fuel and fodder. These trees have adapted to frequent natural and human disturbances, and hence have the ability of sprouting after cutting and lopping. In 1994, examples of such drastic cutting were observed in Hazarganji-Chiltan National Park’s pistachio and ash woodlands where trees recovered in three years.
These woodlands are severely fragmented and have been reduced to small patches due to the interference of man and nature. In several areas, especially between Loralai and Harnai, the trees appear stunted due to overexploitation. Although these species show a remarkable ability to recover after disturbance and they grow relatively faster than other introduced species, the structure and composition of these forests still has been greatly modified by man throughout the centuries. There are only few remnant representative examples in the province and a detailed inventory of these forest communities is not available. It will be difficult to assess the benefits and losses associated with these communities.
2.1.4 Sub-Tropical Deciduous Forests
The salt range and foothills of the Himalayas support sub-tropical deciduous forests. Himalayan foothill sub-tropical forests are the only habitats for Indo-Malayan elements forming multistoried forests with high species diversity. Some typical examples of such forests can be observed in the Margalla Hills, and the Lehtrar, Panjar and Karot Valleys. These forests are formed by tall trees like Kydia calycina, Pistacia integrrima, Bombax ceiba, Albizzia lebbek Terminalia belerica. These are mixed with small and medium-sized trees (e.g. Acacia catechu, Mallotus philipensis, Lannea coromendelica, etc). A large variety of low-growing shrubs, herbs and climbers are also found.
These forests are suffering from land clearing for urban and agricultural expansion, heavy grazing and an increasing demand for fuel wood. The species Holarrhena pubescens is known to be extinct in Pakistan, but has been reported in the Margalla Hills subtropical forests. Some rare species associated with these Himalayan subtropical forests include Pittosporum nepaulense var rawalpindiense, Engelhardtia colebrookkiana, Ficus semicordata and some orchid species such as Nervilia gammieana, Pecteilis gigantea, Eulophia graminea etc.
Vast amounts of sub-tropical forest have been cut down in the lower Swat Valley, with only small patches of the original vegetation remaining on steep slopes or around graveyards (R.R. Stewart, 1967). Extensive plantations of exotic species like Eucalyptus spp. is a growing threat to the natural, indigenous species of flora and fauna
2.1.5 Himalayan Dry and Moist Temperate Forests
Himalayan dry and moist temperate forests are the only tall tree forests and are confined to the high altitudes of the Himalayas and Hindukush Ranges and parts of the Karakorum Range. According to studies in the Kaghan Valley, potential forest area has declined approximately 50% and major structural changes in forests have occurred in more populated areas (Schickoff 1995). In the Siren Valley, the forest cover has decreased by 45% between 1979 and 1988 (GTZ report 1990). This information is based upon remote sensing data (Landsat MSS and TM). Research in the Karakoram Valleys gives evidence of dramatically increased logging in the past 20 years after the construction of the Karakoram Highway and subsequent link roads Schickhoff, 1992, and 1993). According to official estimates, the forests of the Northern Areas will disappear within 30 years if the present rate of logging continues (Government of Pakistan, 1992:10). Allan (1986) and Haigh (1991) reported similar forest losses in the valleys of Swat and Dir.
2.1.6 Trans-Himalayan Plateau
High altitude alpine and sub-alpine habitats are the most sensitive habitats subject to heavy grazing pressure, increasing eco-tourism and global warming. These plateau provide a habitat to many endemic species of plants including two of the three CITES Appendix-I species (Picrorrhiza kurroo and Saussurea costus). The Deosai Plateau is one of the unique habitats in Pakistan providing refuge to the declining population of the Himalayan brown bear (Ursos arctos). Tourism has increased in recent years and increasing vehicle traffic is damaging the vegetation through trampling, in addition to causing noise and vehicular emissions. Detailed ecological studies are needed to assess the vegetation and the impact of disturbance. High alpine areas are sensitive to global climate change. Alpine plant species can be used as indicators of natural and human disturbances.
2.1.7 Thorn Forest
The natural tropical thorn forest of the wood plains, lower hills and arid sandy tract (comprising Salvadora oleoides, Prosopis cineraria, Tamarix aphylla and Caparis decidua) once formed the bulk of the vegetation of the Punjab's so-called wood-reserves (rakhs). After the advent of irrigation, most of the land under these forests was claimed by agriculture, urban colonization and irrigation plantation. At present, the thorn forest community occupies less than 2% of its documented historical record (14,500 km2) and is likely to become vulnerable if existing casual factors continue to operate (Khan, 1994). Two of the three species of these forests, Prosopis cineraria and Tamarix aphylla, have been selected for arid land afforestation. Whereas the co-dominant associate of this community Salvadora oleodies, is specified as an uneconomic wood devoid of any interest (Khan, 1955, 1960, Muhammad and Naz, 1985; Khan and Muhammad, 1987). Its slow growth and the preference for fast-growing species have probably led to its unpopularity and indiscriminate replacement by other trees. This trend is contrary to the historical record, which suggests that it was once a valuable resource in the rural economy. The species now survives or regenerates only on the state-protected arid rangelands on inferior soil and in a degraded state. In these arid areas, it could be considered a biological resource, but even here, S. oleoides is being cleared.
In Pakistan, economic incentives have been far more pervasive in overexploiting this community as opposed to conserving it. The incentives to convert these forests into arable land and to plant artificial forests in the irrigated flood plains might have been appropriate, but on the sandy fragile soil, these practices have set up a trend of Desertification. The costs of reversing the processes of Desertification will far exceed any economic benefits from clearing this vegetation in the first place. Since resource exploitation is governed by economic considerations (McNeely, 1988), an approach to conservation is put forward which may alter land use proposals regarding this species. Ecological and ethno-botanical aspects of this neglected species are highlighted in Rakh Khairewala, located in Thal, a largely man-made desert (Ahmad, 1959; Chaudhri and Sheikh, 1960), and makes a stronger case for promoting the cause for its conservation. The species owes its survival here to security provided by the range and livestock departments, but outside this rakh, Desertification is proceeding rapidly.
2.1.8 The Balochistan Desert Basin
This is the most important but least explored desert basin of the Balochistan province. It starts from Nishi and goes directly to the Taftan Sandak area via Nok Kundi, Dalbadin, Padag, Yarmach etc. A large tract of loess plains interspersed with barren rocky hills is the prevailing feature of the area. The vegetation is sparse, consisting of small shrubs and clumps of grass. This region is very important especially for herpetofauna. A large number of species of snakes and lizards are unique to this area. Endemic species of viper include Ericsticophis macmohoni and lizards of the genus Phrynocephalus. Among the lizard family Teratoscincus scincus, Teratoscincus microlepis, Crossobemon lumsdeni, Eremias scripta, Eremias acutirostris, are characteristic species. Among snakes Eryx tataricus and Lytorhynchus maynardi are also characteristic species of this desert region.
2.1.9 The Thar Desert
This is a plain of gently undulating sand hills sloping upward gradually to the northeast. Elevation generally is below 500 feet. To the south, the desert blends into a vast salt marsh, the Rann of Kutch. Vegetation is generally sparse, consisting of xerophitic and halophytic shrubs and grasses. Acacia, Prosopis, Zizyphus and Calotropis are the characteristic species of the desert region.
The herpetofauna is made up of wide-ranging desert forms. The unique feature of the herpetofauna is the presence of several species characteristic of north central or peninsular India. Here these species are present at the western or northern limit of their distribution. The important species of this region are the tortoises. Testuda elegans (CITES Appendix II) is present; among snakes, Elaphe helenae; among lizards Chemaeleo zeylanicus (CITES Appendix II), Sitana ponticeriana and Agama minor.
The Indus Delta stretches over an area of some 600,000 hectares on the border between Pakistan and India. A vast complex of river channels and creeks, low-lying sandy islands, mangrove swamps and inter-tidal mudflats cover about 200km of the outer edge of the delta. Recent satellite imagery indicates that about 260,000 ha of the delta is covered with mangroves. The progressive reduction of freshwater flows in the Indus has affected the saltiness in the delta creeks. This puts stress on the mangroves causing stunting and the loss of seedlings. Overgrazing and lopping for fuel wood results in stunted trees in some areas. The survival of the mangrove system is at risk. In addition, domestic and industrial effluents flowing into the ecosystem have also contributed to the degradation of the mangrove ecosystem.
The Indus Delta mangroves are perhaps unique in that they constitute the largest area of arid climate mangroves in the world. They are almost wholly dependent upon freshwater discharges from the River Indus, and a small quantity of freshwater from run-off and domestic and industrial effluents from Karachi. The Indus Delta mangrove ecosystem is dominated by a single species, Avicennia marina, which constitutes over 95% of the trees, though a few stands of Ceriops tagal and Aegiceras corniculatum exist. Rhizophora mucronata once used to grow in the Indus Delta but it has since vanished, possibly due to selective overexploitation and degrading conditions. Villagers from many coastal settlements that are scattered throughout the delta, use the mangroves for fuel wood and fodder for their animals. Avicenna leaves are excellent fodder for animals and are collected regularly by the villagers.
The Indus Delta is an important fly-over for migratory birds from as far north as Siberia. In fact, it is one of the seven major migration routes in the world. During the winter, millions of waterfowl, including pelicans and flamingos, stop over in the delta for feeding and breeding. Mammals, jackals and herds of camels can be found on many of the delta's islands. Three species of dolphins can be found swimming in many of its main creeks.