significance of trees in Environmental management

Trees are very important in the environmental management processes through their physical make up and scientific abilities in the pacifying of the natural environment. The role of trees in this process is therefore that they are actively involved in the atmospheric processes, hydrological, biodiversity and soil activities as the paper shall disclose. However, it is important to bear in mind that, the very trees that are pivotal in environmental management processes are the very victims of deforestation and so to speak, the paper shall disclose some of the statistics which shows that environmental management will be a mammoth task if trees are still felled down in the manner they are.

In the definition of terms, there is no universally recognised precise definition of what a tree is, either botanically or in common language. In its broadest sense, a tree is any plant with the general form of an elongated stem, or trunk, which supports the photosynthetic leaves or branches at some distance above the ground. The Hill Shire Council (2004) defined a tree as a perennial plant with a self-supporting woody stem that has a spread of more than three meters or a height of more than six meters or has a trunk diameter of more than three hundred millimetres measured at the base. Environment management is generally an attempt to control human impact on and interaction with the environment in order to preserve natural resources. These definitions give us an insight of the understanding of the relationship of these two components.

In conceptualising the issue, trees have been victims of deforestation for a long period of time around the globe. Trees are cut down and land can be used for settlement, industrial site or farmland and even during war trees are also victims like in the Vietnamese war where it is dubbed as “scorched earth strategy” to starve the enemies thereby crippling the economy. This therefore trickles down to the damage of animal habitat, biodiversity loss, aridity, reduction in bio-sequestration of atmospheric carbon dioxide which leads to global warming among other effects. Deforestation leads to extinction of some species, climatic changes, and desertification and animal, plants and human population displacement. According to the Zimbabwe’s Forestry Commission, the country’s forest will be wiped out in 52 years to come if the rate of deforestation is not curbed. The United Nations Convention on Climate Change (UNCCC 2010), said agriculture is the major cause of deforestation where subsistence farming destroys 48%, commercial farming 32%, logging 14% and fuel wood 5% and it is among poor people because there is no any alternative source for fuel or building material. Other causes of deforestation include corruption of government institutions, inequitable distribution of wealth and power, population growth, overpopulation and urbanisation. According to the United Nations Food and Agricultural Organisation (UNFAO) (2000), the role of population dynamics in a local setting may vary from decisive to negligible and deforestation is a combination of population pressure and stagnating economic, social and technological conditions.

According to the Forest Transition theory, the development level of a country determines its forestry protection. In this theory, a nation in its early or primitive era will be characterised by high forest density (high forest low deforestation) and as the country progressively moves in a Rostowian stagist process, there will be high deforestation and when it reaches maturity stage, there will be moves to protect the environment. However, it is important to realise that this theory is no longer relevant as third world countries are active in environmental management though they have not reached maturity stage. Wilson (2002) said that global deforestation sharply increased and between 7.5million – 8 million square kilometres of the original 15 million – 16 million square kilometres. The UNFAO (2005) said that, the earth’s total forest decreases by 13 million hectares per year and Madagascar has lost 90% of its eastern rain forest. In 2007, Haiti had only remained with 1% of her forest.

Now that the light has been shed on the fate of trees which are important in environmental management processes, it is imperative now to discuss their importance. Deforestation is the major contributor to global warming and is often cited as the major cause of enhanced green- house effect. In this respect, trees therefore play a cleaning role in making sure that all the carbon dioxide and chlorofluorocarbons (CFCs) emitted into the space is engulfed and replaced by useful oxygen. According to the Intergovernmental Panel on Climate Change (2010), trees intercept most of the one-third anthropogenic carbon dioxide emissions. The UK Climate Change Scenarios (UKCIP) (2009), indicate average annual temperature increases between 1 and 5 degrees Celsius by 2080. Trees help cleanse the environment. During photosynthesis, trees absorb, or sequester carbon dioxide and convert it into oxygen for all species to breathe. One acre of trees provides enough oxygen for 18 people, and absorbs as much carbon dioxide as a car produces in 26,000 miles (US Agricultural Department 2008). Trees also remove sulphur dioxide and nitrogen oxide, two major components of acid rain and ozone pollution, from the air.  In this regard when carbon is released from the plant tissue mostly due to deforestation, it escapes into the atmosphere and during this process it reacts with oxygen to give carbon dioxide. Thus trees however, absorb this carbon dioxide during photosynthesis where oxygen will be realised for fauna for survival (Wilson 2002). In the atmosphere, the levels of carbon dioxide is reduced, which when left unchanged it absorb solar radiation that causes a global rise of temperature (global warming). This will have some effects to trees and other species like dissolving ice Polar Regions thereby increasing the frequency and intensity of floods. Thus in environmental management, trees play a pivotal role as they act as a net sink of carbon dioxide for the ecological balance.

In controlling weather fluctuations, trees are very active in transpiration which has a double pronged role of cooling the environment and providing moisture in the atmosphere for rainfall formation. In transpiration, trees release water molecules into the space which thereby leaves a cooling effect on the surrounding environment. Trees are natural buffers to harsh weather conditions. Well-forested lands are consistently at least 2 to 4 degrees cooler during the summer and 1 to 2 degrees warmer during the winter than deforested land (Zimbabwe’s Forest Commission 2012). This temperature reduction can significantly lower smog production, according to the U.S. Department of Energy. Trees can reduce wind speeds by up to 85%, compared to treeless areas. This is also evidenced in the dense forests of Zimbabwe’s eastern Highlands and Amazon forest in Brazil basin where there is high evapotranspiration and also mild temperatures. This then has an environmental effect as the surrounding fauna experiences cooler temperature which do not restrain them from their normal chores like grazers and herbivores from grazing and herbivores respectively and decomposers which thus lead to ecological balance.

In rainfall formation, trees produce most of the moisture which rises into the space for condensation to take place with the aid of sodium iodide participles commonly known as condensation nuclei. In this view, trees contribute a lot to the environmental management process as it is pivotal in the provisioning role of transpiration which contributes to rainfall, which is commonly known as “water is life”. This is then commonly seen in Zimbabwe on its western part, which has sparse vegetation and receives unpredicted rainfall. It is in Matebeleland region which is classified as in region 5 whereas eastern Highlands is in region 1 and 2 due to amount of rainfall and vegetation cover. This then means that trees play an important role because their capability in provisioning service of water vapour which maintains the environment’s life in its fullness with which lack of water will lead to environmental collapse.

In line with Brundtland Commission which points out the interdependence among pillars of sustainable development, of which trees are part of environmental pillar implies that trees are important in environmental management process. If the ecological footprint is to be taken into account, trees also are a part which is to be considered important as they link the natural environment and the atmospheric processes in backward and forward linkages. Trees are also important in air cleaning where it has been largely polluted by human activities ranging from farming, industrial, factory and domestic. This is mostly done by urban trees which are exposed to the circumstance. According to Freer-Smith et al (2005), urban trees can make significant contributions to improving air quality by removing air impurities through dry deposition, a mechanism by which pollutants are deposited on plant leaf surfaces. This is seen at most trees close to industrial sites like cotton ginnery in Nembudzia where particles of processed lint at evergreen Jatropha trees are seen. These particles then are deposited into the soil when a tree sheds off its leaves and the very deposits will be processed into useful nutrients in the soil, which will be then be used by the same trees and other organisms for the healthy environment. With this school of thought, it is important to note that trees play an important role in the environmental processes as they convert the toxic particles which jeopardise even human beings and convert them to useful nutrients thus maintaining an ecological balance.

According to the Ecological Modernisation of the 1990s, Mol and Spaargaren (2000) said that, trees are helpful in urban areas in terms of the formation of urban heat islands. In this regard, human activities especially emissions from industrial actions and refrigeration and trees transpire water vapour into the space which mixes with hydro nuclei which aid in condensation process. In this regard, an urban city such as Harare or Gweru or even any other city can receive rainfall whilst other adjacent areas cannot, which create a different climate and  sustains the local environment. From this school of thought, it has been made clear that trees are important in environmental management processes as they facilitate the emergence and upholding of ecology. As Escobedo and Andreu (2015) said, trees mitigate the negative effects of urban development and improve environmental quality and ecological services, thus there is need for ecological rationality. This reduces ecological collapse as decoupling or delinking of material flows from economic flows.

Trees also act as buffers against noise pollution mostly in the urban set up. Green space has the ability to mitigate noise in urban areas. Hosseini and Maleki (2011) said that, planting "noise buffers" composed of trees and shrubs can reduce noise by five to ten decibels for every 30m width of woodland, especially sharp tones, and this reduces noise to the human ear by approximately 50%. To achieve this effect, the species and the planting design must be chosen carefully. The effective management and extension and creation of new woodland areas helps to screen noise and pollution, restore and enhance degraded landscapes, provide recreational opportunities, improve health and well-being and also help mitigate climate change and contribute to floodplain management. The successful growth of trees in urban areas is dependent on a number of factors, including the species type. The Right Tree for a Changing Climate database can help to determine the most appropriate tree for a location and aid in the management of trees in urban green space. This was done and became successful in East London, along the Thames Gateway, South Essex (The Hill Shire Council 2014). As a bonus, trees also provide habitat for birds, whose twittering add to the pleasant background sounds. A properly-designed buffer of trees and shrubs can reduce noise by about five to ten decibels or about 50% as perceived by the human ear, according to the USDA National Agroforestry Centre.

The International Tropical Timber Organisation report (2012) set up the seven Sustainable Forest Management Standards of which biodiversity, is also part of that. It is important also to take a glance on the role trees play in biodiversity which is an important component of the environment that other species cannot survive if it is tempered with without sustainability. Trees provide habitats for various wildlife species. In this regard, it is important to note that, various trees provide materials for nest building like local yellow wood trees, Mopani trees, baobab trees among others which most birds like all classes of eagles, doves, blue birds, the secretary bird among others usually make their nest on. Not only do they provide twigs and leaves for habitat formation but also some trees like dry Mopani tree braches, mupfuti, mutondo among others are easy to be drill by some birds like the commonly known chigogodza bird which make the nest by hollowing the trees trunk as its habitat. Some trees have thorns and pricks that some birds are able to live on while some predators cannot penetrate to pounce on them which is another role trees play in balancing the ecology which therefore lead to better environment that is rich with all forms of lives. However, it is not only do wildlife benefit from trees provisioning of that but do human beings also fell trees to get building materials. Some people also make beehives from the tree barks like mupfuti so that bees also get shelter to live on and it is also important to realise that bees and other insects do not necessarily dependent on human beings for shelter but rather they do look out for holes on other trees. From this analysis it has been made clear that trees play a great fundamental role in the environmental management process by ensuring habits and sustaining the lives of other animals which are completely dependent upon the very existent of trees.

Still in the biodiversity role of trees, it is important to note that there are various kinds of trees that provide food in form of fruits and leaves to other animals and birds. As all animals other than carnivores, omnivores and scavengers often rely on tree species for survival, trees completely come to that aid. Tree species whether indigenous or exotic provide food to animals like squiggles, rodents, giraffes, baboons, monkeys, chimpanzees, gorillas, kudus, hoto, husvu, to name but a few get food from trees all year round. In this regard it is also important to keep in mind the fact that trees through their provisioning role of food sometimes get destroyed by gigantic wildlife animals like elephants and rhinoceros which have for examples destroyed the Gonarezhou National Park in Zimbabwe thus the local authorities have resorted to relocation of some elephant herds to enhance ecological footprint balance of the park.  According to Tafangenyasha (1996), said that in Gonarezhou National Park from 1970-1983 trees population declined with 30.1% (in 13 years) at an annual rate of 2.3%. Most of the endangered tree species are: Brachystegia, Julbernadia, Isoberlinia, Colophospermum, some Combretum, Terminalia. It is also important to realise that trees provide food in different seasons of the year which gives a reproductive cycle to different forms of life i.e birds and animal species, for example, most birds reproduce from early March to mid-June where food is available and animals reproduce from end of August to end of November where trees have shed off their leaves and twigs which are useful in habitat building by some birds like eagles and ravens as well as rodents and mice. However, it is important to realise that not only do wildlife benefit from trees for food but also human beings as they get edible fruits and roots for eating and herbs for technical medicine and traditional or home use. In this regard, it has been made clear that, trees play a pivotal role in environmental management through provisioning role for human beings, domestic animals, and wild life species.     

In foregoing with biodiversity role, trees are important in the boosting of the nutrient levels of the soil. In this school of thought, it has been observed that when trees shed off their leaves mainly during the winter and spring season of the year, those leaves are spread out on the land waiting for the rains in the summer where decomposers will work upon them. In this regard small animals like eelworms, bacteria, fungi will be catalysts and facilitators of the process. It is known that, trees are storages of carbon and nitrogen which are also important for carbon and nutrient cycles. They provide with such inputs which when they are successfully worked upon, trees themselves, grasses and other animals and insects will have food and nutrients for their up keep (Porter et al 2008). However, it is also important to realise that human beings, especially rural farmers, collect humus or mulch from the forest which are products of trees and apply them in the fields to boost their harvest. Thus they can realise bumper harvest which means that when households have adequate food they will not abnormally stalk upon trees excessively for food, thus the environment can remain healthy, balanced, productive and sustainable. In this regard, it has been noted that trees play a tireless role in the environmental management process by providing vital inputs for soil fertility and growth of themselves, grasses and small animal species as well as human beings which is very critical for environmental sustainability.

In the protection role, trees are the main natural and human favoured actors against soil erosion. In this regard, it has been noted that trees with firstly their leaves intercept a lot of water during the storms. The water will not hit the ground with great intensity which prevents  splash erosion. When water is intercepted, some will reach the ground with reduced intensity, some through dripping as it follows braches and stems to the ground and some is held there for many hours and may evaporate back to the atmosphere and some is taken up by insects and small birds for their daily living. It has been noted that coniferous trees intercept 25-35% of precipitation and deciduous fruits also 15-25% (Reid and Lewis 2007). Also, it has been observed by Reid and Lewis (2007) that, 22.4% is intercepted and evaporated by the forest canopy and average interception loss remains above 20%. Even for the largest storms  peak flows from below-canopy rainfall suggest that altered interception and transpiration could account for the 54 to 70% average increase in peak flow. About 46% of the interception loss occurs through post-storm evaporation from foliage and 54% is either evaporated during the storm or enters long-term storage in bark. In Santa Monica, Annual rainfall interception by the 29,299 street and park trees was 193,168 square metres (6.6 square metres/tree), or 1.6% of total precipitation. The annual value of avoided storm water treatment and flood control costs associated with reduced runoff was $110,890 ($3.60/tree). Interception rate varied with tree species and sizes. Rainfall interception ranged from 15.3% (0.8 square metres/tree) for a small Jacaranda mimosifolia (3.5 cm diameter at breast height) to 66.5% (20.8 square metres/tree) for a mature Tristania conferta (38.1 cm). In a 25-year storm, interception by all street and park trees was 12,139.5 m3 (0.4%), each tree yielding $0.60 (0.4 squares metres/tree) in avoided flood control costs. Rainfall interception varied seasonally, averaging 14.8% during a 21.7 mm winter storm and 79.5% during a 20.3 mm summer storm for a large, deciduous Platanus acerifolia tree (Xiao and McPherson 2003). In terms of roots vitality, it has been noted that roots facilitates water dripping, ground seepages, infiltration and percolation thereby reducing surface water run off which often lead to the formation of gullies and dongas. All these processes of ground water movement are very critical as they curb against soil erosion which has resulted in the loss of very useful lands in Zimbabwe that could have been productively used for settlement, industry, farmland or wildlife habitat. It has been observed that tracks of lands that have densely populated trees have low risks of soil erosion than those areas with little to no vegetation. However, it has been ironically observed that in the tropical regions like the Congo and Amazon Basins, big trees have choked up some small species varieties of trees and grasses in phototropism competition which has also led to the reduction of some important plant species. Despite this are disadvantages, it has been made clear that trees are very important in environmental management process as they reduces the potential loss of land to soil erosion through leaves and roots activities.

In hydrological role, trees are very important as through leaves activities, they transpire water vapour into the atmosphere, which is critical for rainfall formation. The rainfall will then supply water for all forms of life in the environment. Also, trees with their roots facilitate infiltration of water into the ground which leads a rise in the water table thereby allowing themselves to reach water and other plant species to reach for water. Also, if infiltration has taken place on a large scale in other areas like mountainous regions of eastern Highlands in Zimbabwe it leads to seepages and sponge areas which provide animals with water for daily living. Also, if infiltration is greatly facilitated it allows human beings to sink boreholes and dig wells for water. With regards to the hydrological cycle, trees play an important role in also cleaning water through infiltration with the aid of soil so that all species can get clean water. From this school of thought it has been noted that the hydrological cycle is incomplete if trees are left out as they ensure water availability to all species on the mother earth.

Paradoxically, it is important to note that though trees are helpful in environmental management processes sometimes they retard the very nascent efforts especially of human beings which result in them being felled down. In urban areas, trees because of their leaf drop cause filthiness on the ground and roof tops thereby leaving impurities. Also, tree roots tend to cause bending and crumbling of the infrastructure like tarred roads, drainages, canals, walls among others with their effects resulting in the jeopardising of human health in the form of pipe bursting (sewer and clean water), wall cracks. This is also seen at MSU tarred ground tree roots have caused crumbling of the infrastructure. In the rural areas has been observed that, some trees have thorns which neuter peoples carts, cars, bicycles and even human beings and their domestic animals causing disruptions in the daily lives of the people. With this, the result is the down-right felling of trees which are considered as precarious to livelihood of the people thereby depletes some species of trees which are important in the ecological balance. With this school of thought it can be said that though trees are very pertinent in environmental management, some species are victims because of their unwanted repercussions. Thus people in general are caught up in between where on the other hand there is a pressing need for conserving and protecting the environment (trees) and on the other the need to live a healthy and safe environment by felling them. This however, is a cause for concern in any given set up of the society as people suffer differently as a result of some trees.

To conclude, it has been noted that, trees are very fundamental in all environmental processes through their provisioning, regulation, supporting and cultural roles in four pronged areas of atmospheric, biodiversity, soil and hydrological facilities. Also, it has been realised that, though trees are important in any given environment, they are the very victims of deforestation since time immemorial due to human activities which sometimes trigger natural hazards and some of them are a result of gigantic animal activities in quest for survival. However, also trees in trying to balance the ecology end up disrupting human activities which when develop will graduate into protecting the environment and thus some tree species end up being felled down.