POST TIME: 30 August, 2018 10:24:26 AM
Forests needed more ever than before
Nearly half of all known species live in forests, including 80 per cent of biodiversity on land
Mohammed Abul Kalam, PhD

Forests needed more ever than before

Forests cover a third of all land on Earth, providing vital organic infrastructure for some of the planet's densest, most diverse collections of life. They support countless species as well as 1.6 billion human livelihoods, yet humans are also responsible for widespread deforestation, clearing millions of forested acres every year.
The United Nations declared March 21 the International Day of Forests in late 2012, part of a global effort to publicize both the value and plight of woodlands around the world. It was first celebrated March 21, 2013, nestling in between the U.N.'s International Day of Happiness on March 20 and World Water Day March 22.
Forests pump out oxygen we need to live and absorb the carbon dioxide we exhale (or emit). A single mature, leafy tree is estimated to produce a day’s supply of oxygen for anywhere from two to 10 people. Phytoplanktons are more prolific, providing half of Earth's oxygen, but forests are still a key source of quality air.
Nearly half of all known species live in forests, including 80 percent of biodiversity on land. That variety is especially rich in tropical rain forests, from rare parrots to endangered apes, but forests teem with life around the planet: Bugs and worms work nutrients into soil, bees and birds spread pollen and seeds, and keystone species like wolves and big cats keep hungry herbivores in check.

Some 300 million people live in forests worldwide, including an estimated 60 million indigenous people whose survival depends almost entirely on native woods. Many millions more live along or near forest fringes, but even just a scattering of urban trees can raise property values and lower crime.

By growing a canopy to hog sunlight, trees also create vital oases of shade on the ground. Urban trees help buildings stay cool, reducing the need for electric fans or air conditioners, while large forests can tackle daunting tasks like curbing a city's "heat island" effect or regulating regional temperatures.

Trees also have another way to beat the heat: absorb CO2 that fuels global warming. Plants always need some CO2 for photosynthesis, but Earth's air is now so thick with extra emissions that forests fight global warming just by breathing. CO2 is stored in wood, leaves and soil, often for centuries.

Large forests can influence regional weather patterns and even create their own microclimates. The Amazon, for example, generates atmospheric conditions that not only promote regular rainfall there and in nearby farmland, but potentially as far away as the Great Plains of North America.

Tree roots are key allies in heavy rain, especially for low-lying areas like river plains. They help the ground absorb more of a flash flood, reducing soil loss and property damage by slowing the flow.

On top of flood control, soaking up surface runoff also protects ecosystems downstream. Modern storm water increasingly carries toxic chemicals, from gasoline and lawn fertilizer to pesticides and pig manure, that accumulate through watersheds and eventually create low-oxygen "dead zones."

Forests are like giant sponges, catching runoff rather than letting it roll across the surface, but they can't absorb all of it. Water that gets past their roots trickles down into aquifers, replenishing groundwater supplies that are important for drinking, sanitation and irrigation around the world.

Farming near a forest has lots of benefits, like bats and songbirds that eat insects or owls and foxes that eat rats. But groups of trees can also serve as a windbreak, providing a buffer for wind-sensitive crops. And beyond protecting those plants, less wind also makes it easier for bees to pollinate them.

A forest's root network stabilizes huge amounts of soil, bracing the entire ecosystem's foundation against erosion by wind or water. Not only does deforestation disrupt all that, but the ensuing soil erosion can trigger new, life-threatening problems like landslides and dust storms.

In addition to holding soil in place, forests may also use phytoremediation to clean out certain pollutants. Trees can either sequester the toxins away or degrade them to be less dangerous. This is a helpful skill, letting trees absorb sewage overflows, roadside spills or contaminated runoff.

We herald houseplants for purifying the air, but don't forget forests. They can clean up air pollution on a much larger scale, and not just the aforementioned CO2. Trees catch and soak in a wide range of airborne pollutants, including carbon monoxide, sulfur dioxide and nitrogen dioxide.  Sound fades in forests, making trees a popular natural noise barrier. The muffling effect is largely due to rustling leaves — plus other woodland white noise, like bird songs — and just a few well-placed trees can cut background sound by 5 to 10 decibels, or about 50 percent as heard by human ears.

Not only do trees provide fruits, nuts, seeds and sap, but they also enable a cornucopia near the forest floor, from edible mushrooms, berries and beetles to larger game like deer, turkeys, rabbits and fish.

Forests provide a wealth of natural medicines and increasingly inspire synthetic spin-offs. The asthma drug theophylline comes from cacao trees, for example, while a compound in eastern red cedar needles has been found to fight MRSA, a type of staph infection that resists many antibiotic drugs. About 70 percent of all known plants with cancer-fighting properties occur only in rain forests.

Where would humans be without timber and resin? We've long used these renewable resources to make everything from paper and furniture to homes and clothing, but we also have a history of getting carried away, leading to overuse and deforestation. Thanks to the growth of tree farming and sustainable forestry, though, it's becoming easier to find responsibly sourced tree products.

More than 1.6 billion people rely on forests to some extent for their livelihoods, according to the U.N., and 10 million are directly employed in forest management or conservation. Forests contribute about 1 percent of the global gross domestic product through timber production and non-timber products, the latter of which alone support up to 80 percent of the population in many developing countries.

Natural beauty may be the most obvious and yet least tangible benefit a forest offers. The abstract blend of shade, greenery, activity and tranquility can yield concrete advantages for people, however, like convincing us to appreciate and preserve old-growth forests for future generations.

Forests really tie everything together — and we often don't appreciate them until they're gone. Beyond all their specific ecological perks, they've reigned for eons as Earth's most successful setting for life on land. Our species probably couldn't live without them, but it's up to us to make sure we never have to try. The more we enjoy and understand forests, the less likely we are to miss them for the trees.

Preservation of forests and woodlands is extremely important for the supply of forest food. If rural populations in developing countries lose their access to forest food and medicine, e.g., due to deforestation or ecosystem degradation, this may lead to food insecurity, malnutrition, and disease. Forests also serve as important genetic reservoirs for plants and animals that have potential use for food and medicine. In order to use forest food to complement diets in balanced ways, more knowledge is needed on the nutritional values of different types of forest food. The traditional knowledge of indigenous people and local communities in gathering and hunting of forest foods and medicinal forest plant species should be paid more attention to. In local communities the approach is holistic, for example, there is no clear distinction between medicine and healthy food. In addition, forest management practices that can preserve the valuable species and their nutritional value need to be developed and studied

Forest-related diseases and hazards: Our innate attraction to forests, part of a phenomenon known as "biophilia," is still in the relatively early stages of scientific explanation. We know biophilia draws humans to water, woods and other natural scenery, though, and exposure to forests has been shown to boost creativity, suppress attention deficit/hyperactivity disorder (ADHD). ADHD, speed up recovery, and encourage meditation and mindfulness. Environmental modifications -- such as changes made to minimize the impact of ADHD in day-to-day living which forests can provide. It may even help us live longer.

The natural environment and compounds derived from woodlands have an abundance of positive effects on human physical and mental health. Forest environments may, however, also pose risks to human health. People living in forests or otherwise having frequent contact with forests may be exposed to forest-related infectious diseases. The lifecycle of many infectious diseases involve the pathogen, the vector, and the human. The vectors are often insects, but can also be mammals. Many infectious diseases such as Puumala virus (PUUV), Lyme borreliosis, Hantavirus cardiopulmonary syndrome (HCPS), and malaria, are associated with forests, which are the preferred habitat for vector and host populations. Infectious diseases are severe, especially in tropical regions, but for example tick-borne diseases, such as Lyme disease and tick-borne encephalitis, occur outside tropical regions. Emergence of infectious diseases is linked among other things to deforestation, loss of biodiversity, habitat alteration, and human migration. Human-induced land-use changes are often considered as the primary drivers of infectious disease outbreaks; for example, the increased risk for Lyme disease in northeastern USA is connected with forest fragmentation, urban sprawl, and biodiversity loss. Ecosystem alterations affect the emergence of the diseases by changing the ecological system as well as the habitats of hosts or vectors and parasites. Modification of forest ecosystems—for example, deforestation, forest fragmentation, and biodiversity degradation—beyond a certain threshold may increase the risk of disease transmission. Increased edge effect can promote interaction among pathogens, vectors, and hosts as well as the population growth of vectors and hosts. Also reforestation may increase the risk for zoonoses in some areas, for example, in Europe.

There is clear evidence that forest clearance affects the emergence of infectious diseases. Deforestation has coincided with an increase of malaria and/or it vectors in Africa, Asia, and Latin America; for example, in South America, deforestation or activities associated with it have produced new habitats for Anopheles darlingi mosquitoes and have caused malaria epidemics. The destruction of forest habitat can also result in the replacement of the most common vector species with a more effective vector; for example, when overall mosquito diversity decreases, the surviving dominant species are usually more effective vectors for malaria.

The relationships between forest ecosystem and disease transmission are complicated. Modification of forest ecosystems may be necessary, but is rarely sufficient to increase disease transmission or to generate an epidemic. Still more research efforts are needed to clarify how forests can be used in regulating the emergence of infectious diseases. Climate change may enlarge the occurrence area of infectious diseases. Several models suggest that global warming may lead to increasing risk of vector-borne disease, but caution is needed when interpreting these results.

Forests also include other risks to human health; for example, forests expose people to physical hazards such as forest fires, floods, drought, soil slides, and haze. Forests also include dangerous wildlife and toxic fruits, foliage, and fungi. Forests include flora and fauna that can provoke allergic or irritant reactions, for example, bites of insects and snakes may cause simple localized reactions or serious systemic reactions in sensitive people. The pollen from trees, shrubs, weeds, and grasses is one of the main causes of allergy, and there is a clear need to identify nonallergenic or low-allergenic trees and other plants when designing parks or managing urban forests.

In recent years, the fundamental effect of forests on human health and well-being has been acknowledged to a greater extent. There are currently numerous cross-sectoral initiatives that promote the work in the field of forests and human health and the integration of the research results into the practice. There is also an abundance of existing research on the relationships between human health and forests.

The former Head, Department of Medical Sociology

Institute of Epidemiology, Disease Control & Research (IEDCR)

Dhaka, Bangladesh E-mail: med_sociology_iedcr@yahoo.com