Greening of Urban Jungle – Wahidul Islam and Ifrith Islam
Urban agriculture, as opposed to rural agriculture, means more greenery in cities. But the authorities concerned are yet to change their mind in greening the ever expanding urban areas in Bangladesh. Metropolitan agricultures are in the bottom of the list of priority of the department of agricultural extension popularly known as DAE. The policy makers think much about rural agriculture which would cater to all the demands of the metropolitan dwellers. For sure, Bangladeshi farmers are out there in the rural areas to have produces enough to provide their city brothers and sisters. The agricultural department hasn’t thought that these farmers can’t provide oxygen either in cylinders or through pipeline to the city dwellers particularly to the inner part of a metropolitan. It sounds unthinkable still. A person inhales 7 or 8 liters of air per minute. The percentage of oxygen in the air is about 20%. But when you exhale, your breath consists of 15% oxygen, so you consumed about 5%. Therefore, a person uses about 550 liters of pure oxygen each day which is not available in increasingly industrialized cities particularly in Dhaka.
Why green metropolitan
is a must
Six molecules of carbon-dioxide to produce one molecule of glucose by photosynthesis, and six molecules of oxygen are released as a by-product. A glucose molecule contains six carbon atoms, so that’s a net gain of one molecule of oxygen for every atom of carbon added to the tree. A mature sycamore tree might be around 12m tall and weigh two tonnes, including the roots and leaves. If it grows by five per cent each year, it will produce around 100kg of wood, of which 38kg will be carbon. Allowing for the relative molecular weights of oxygen and carbon, this equates to 100kg of oxygen per tree per year.
How many trees does humanity need?
There are as many as seven billion people all over the world. A human breathes about 9.5 tonnes of air in a year, but oxygen only makes up about 23 percent of that air, by mass, and we only extract a little over a third of the oxygen from each breath. That works out to a total of about 740kg of oxygen per year. That is, very roughly, seven or eight trees’ worth. So the whole world needs roughly fifty billion trees for better breathing. So counting trees on the planet is not an act of fooling, isn’t it? We don’t know how many trees were when our lush green planet Earth was ready for habitation or how many need it to sprout again to make it into ‘jannah’ ‘hadikah’ which mean garden or green in Arabic.
So, have you found your favourite tree as your blessing?
Well, we will never know…
There are so many trees and of them some we know and many we don’t, especially the young generation. When they are old enough to hang out with friends, they go for walk to a nearby lake or different places for sightseeing or to the Botanical Garden then sometimes they can learn the various name of the trees either from a knowledgeable friends or from the name tag on the trees.
People can grow trees as a hobby or out of necessity. In some cases hedge plants are grown for security reason, i.e. to stop outsiders from trespassing. Tree planting hobby is one of the most popular one because nature gives a type of pleasant feeling that nature lovers don’t find it easily among others. Different types of trees can be nurtured in pots on verandas. But not all types of trees are possible to grow on rooftop. Trees like mango, carambola, star fruit, grape, pamello, wood apple if we know which kinds of trees need what amount of space and soil.
The Greening of Rooftops
According to the Department of Agricultural Extension, there are around 6000 rooftop gardens in the Dhaka city which is home to more than four lakh buildings. Government has divided the Dhaka city in three five areas supervised by its five offices called Metropolitan Gulshan, Metropolitan Mirpur, Metropolitan Muhammadpur, Metropolitan Uttara and Metropolitan Kamrangirchar, said sources in Metropolitan Mohammadpur office in Shankar area. Among them only Mohammadpur office has over 1000 beneficiaries.
Vegetables, Fruits And Flowers Compete For Space On Rooftops
Vegetables, fruits and flowers that can be grown on their roofs include aubergine, tomato, bottle gourd, ash gourd, beans, pumpkin, basil, coriander, capsicum, chilli, bean, mango, sweet tamarind, litchi, banana, lemon, orange, guava, olive, strawberry, varieties of seasonal flowers, cacti and orchids.
On rooftop, larger plastic barrels can be cut off to make bigger pots or the usual terra-cotta containers. The wooden boxes, high stoneware clay and the fiberglass are also highly useable. The heavy type containers should be placed near the load-bearing walls or over a load-bearing beam or joist as these can take more weight than unsupported areas. Also the containers should be placed in such way that anything doesn’t block the oozing of surplus water. In Dhaka it is hard to find the right kind of soil for the right kind of plants. But from nursery we can buy a bag of average good soil rather than cherry-picking from here and there because pure soils are unavailable in this metropolitan city. Collecting soil from a nursery, it is beneficial because the soil is premixed with organic formulations. Sometimes you need no fertilizer as only soil nutrients are enough.
Sunny and Windy Gardens
The wind is unceasing. On sunny, hot days we call it refreshing breeze. But cold isn’t the issue for the plants in a tropical country; wind dries the leaves and they are not watered once a day in summer, plants will die soon. Plants that are tolerant of wind and sun tend to have leaf modifications. It results in reduced surface evaporation, e.g. plants with needle-like leaves (pines, grasses or brooms) or even small leaves. Dwarf spring-flowering bulbs can also tolerate exposed sites. Gardeners in high rises tend to water houseplants once a day, but they don’t! So, most professional gardeners ask the building owner to install drip irrigation on any balcony or terrace. But an outdoor water supply, a two-inch pipe can be used as that easily runs all the way around perimeter of the garden. Children love water so they can come handy where watering the garden is concerned. Hence their `help’ is really time- consuming sometimes. Most herbs don’t need rich soil but sometimes better compost won’t do any harm. Gardeners feel bad to throw away the garden waste and pay to have them hauled away and then turn around and pay for bagged compost.
Climbing or Creeping Plants
If we talk about rooftop plantation the walls of the concrete jungle will take it otherwise. City walls are much bigger than those of city rooftops. The higher the high-rise building bigger the city walls but the size of the rooftops remains the same whatever high goes the skyscraper. The only problem is they are steep. So climbing plants are the answers to wall plantation they will be easy on eyes. On land creepers are chosen for their suitability to clothe a pergola in the garden but to grow them on wall structures one need some scaffolding or structures to support the creeping plants and vegetables. In growing you need to be careful. A single climber may be the most effective way to cover a wall. Rough cast walls are helpful for creepers but to grow vegetable producing creepers you need to create some pergola like steel structure for their support. Too many climbers all vying for attention may produce an unsatisfactory result in case of bigger walls it is possible. And for the better growth intensive care is necessary. Cornices (a decorative border found where the ceiling meets the walls in some rooms and also along the top of some walls and buildings) can be used for different floors. Pots can be placed on the cornices of different levels of a building to use the full spaces. Hose, ladder, harvesting equipment must be there for taking proper care of the creepers.
There are a lot of climbing plants which give a very remarkable view such as sugar snap peas, bottle gourd, bitter gourd, drum stick, chickpea, pumpkin, beans among the vegetable creepers.
Among the flowers there are moonflowers, bougainvillea, ivies and clematis for wall plantation. Ivy-clad buildings are attractive. Ivy, there are two types of that people grow- Boston ivy and English ivy. The English ivy does not need any help to grow up the wall as it uses root that digs into plaster but it destroys that side of building. They must be controlled around gutters, roof lines and exterior window casings, trim and shutters. Whereas Boston ivy looks great climbing up the walls even though it is not evergreen but it turns pretty colours and drop leaves in the fall and won’t destroy walls.
Vines grown on the masonry surface of a structure or home can reduce the surface temperatures of the wall and provide an effective way to reduce the problems of heat gain in west facing walls. They also create a more comfortable exterior space nest to the building. Vines add striking visual interest and vibrant greenery to the home landscape. They can cover an unsightly masonry wall as well as provide for birds and small wildlife.
All climbing plants will need some training initially. When planting a new climber at least 30-45cm away from the base of the wall so that rain can reach the roots of the plant. Using a series of horizontal or vertical wires, or a trellis attached to the wall to provide support for the climbing plants. Tie in new shoots with soft garden twine. Garden structures for the climbing plants need to be strong and secure as plants can become very heavy while bearing fruits. A rope ladder is necessary to climb across the wall of the building so that the unnecessary part of the vine can be structured into fine creative wall decoration.
Plants That Grow With Less or No Sunlight
A wide spectrum of cacti, mint, begonias, philodendron, bromeliad grow better in less sunny places. These plants are like introvert boys or girls who like withdraw themselves in the corner of a room, busying themselves with gadgets. These plants are opposite of sunny plants.
The Mother-in-law’s Tongue (Snake Plant), Lucky Bamboo and Maidenhair ferns are the plants that can grow exceptionally well without sunlight and it can purify the air at home.
Peace lily needs regular watering as they flourish and lend a calm ambiance to home. Spider plant and Dracaena need watering as well.
Peace LilyMother-in-law’s Tongue
Devil’s Ivy (Money Plant)
Then, there is the Devil’s Ivy (pothos), which is a climber with a little bit of support and grows without sunlight. And also purify the air of carbon monoxide. Trimming and watering is necessary periodically to keep the pothos looking full and luscious.
Building-Integrated Food Chain in Inner City:
Beyond energy cost, there are additional vulnerabilities in our conventional food-production system. Crisis like strikes, natural calamities like too much rain, little rain and even flood in the north disrupts communication and in the long-term, reduction of flows water from the upstream will cause water shortage in Bangladesh and its primary vegetable-producing regions. These vulnerabilities are reviving interest in the growing food locally and even on the rooftops.
Most of our children growing up in the cities have forgotten swimming like have had no relationship with mother earth. They have never seen a spinach and or goat being grown, picked a tomato from the garden, or watched chickens scratching in the soil perhaps on the TV screen only. It makes our future generation aware about environment on which have to and will depend on for so many natural products.
Animals on Rooftops
Goat Farming and Gardening in the rooftop in Dhaka may go hand in hand. It may draw the future roadmap to supply animal proteins to the inner city. Rooftop farms have the potential to use millions of gallons of rainwater avoiding the dependence on the city’s WASA like stuffs. Black Bengal goats have additional advantage of having 2-3 kid every 6 months and highly prolific. Its meat has high demand in the city super market. Although, don’t grow faster as compared to those of Boer and Jamunapari its meat flavor is adored by the consumers. In addition, goat milk having its unique character of low allergen and for smaller fat structure is an ideal drink for the babies who are sensitive to soy and other milk and milk products. The most important part is that the inner city pollution has had brought asthma to our city dwellers. Goat milk relieves asthma for unknown reasons. As a result, rooftop goat farming is gathering popularity. Norwegian milking goats are capable of producing over a litre of milk per day is a very good choice. Recently, Boer goats have started growing in Bangladesh as it is a specialist meat breed introduced to Australia from South Africa.
Low Carbon Emission
The more the inner city goes green the less the emission of carbon will be. This means, fewer trucks on road and highways to carry food for the cities and the lower greenhouse gas emissions. In addition, rooftop gardening models, may have other benefits – plentiful sun and an absence of traditional pests. The farm is established in the compost produced from goat pellet. Because the thick bed of rich compost and the impermeable layer beneath, this place almost never has to irrigate. The compost is safe- free of herbicides often used on lawns, for example-by controlling exactly what gets composted.
A community approach (self-help basis) rearing of poultry, pigeons, koels on the rooftop has been on-going for some years in Dhaka city. This is contributing to strengthen the economies by ensuring some kind of food safety. If pragmatic approach is taken, this will help nourishing and protecting soil, plants and animals in a concerted way. In some houses fish culturing and grass production in water is going on in this space-constrained mega city.
Real and professional farmers have nothing to be antagonistic to these amateur urban farmers. Professionally grown produces in rural Bangladesh may be only directed to export. Agricultural corporate may grow in villages keeping eye on international markets. City corporations and other authorities concerned should come up shooting the legal and institutional stumbling blocks to popularize metropolitan agriculture. The greening of city may transform least livable Dhaka into more livable one.