
Thursday 15 February
The World's Favourite Unloved Species 2018 - the Galapagos Racer
In the simplest terms, forests are areas of land covered with trees and undergrowth. However, while it is true that forest landscapes are dominated by trees, in reality these ecosystems are far more complex than they may first appear, supporting a whole host of different species and playing an important part in human livelihoods.
Interestingly, forests occupy one third of the Earth’s land area, yet incredibly house around 80 percent of the world’s terrestrial biodiversity, from birds and mammals to amphibians and invertebrates. There are many different types of forest around the world, with temperature, rainfall and soil composition all determining which type will grow in a particular area.
Tropical rainforests contain the greatest species diversity of all biomes on Earth, and are thought to be the world’s oldest living ecosystems. Found near the equator in Africa, Asia and Central and South America, these are lush, dense forests characterised by consistently heavy rainfall and year-round high temperatures of between 18 and 25 degrees Celsius.
In a single year, a tropical rainforest can experience an impressive 254 centimetres of rain, often causing nutrients to leach from the soil. This, combined with the lack of light penetrating through the trees, means that very few plants grow on the forest floor, which is instead mostly covered with soil and dead plants. Decomposition occurs at an extremely rapid rate in tropical rainforests as a result of the warm temperatures and moist air. However, despite being somewhat deficient in living plant matter, the forest floor is home to some rather charismatic species such as the okapi (Okapia johnstoni), which roams the rainforests of the Democratic Republic of the Congo in search of the leaves, fruits and fungi on which it feeds.
The understory or ‘shrub layer’ of the tropical rainforest is the next level up from the forest floor, and typically contains small trees or bushes that rarely exceed 3.5 metres in height. These plants tend to have large leaves to trap as much sunlight as possible in the dingy lower regions of the forest. Many animal species inhabit the understory, from the powerful jaguar (Panthera onca) to tiny invertebrates and treefrogs, such as the large-eyed lemur leaf frog (Hylomantis lemur).
The primary layer of the forest which forms a dense roof over the ferns, mosses and vines of the understory and forest floor is known as the canopy. The canopy is typically formed of broadleaf trees which grow to impressive heights of 25 to 35 metres, such as the white seraya (Parashorea macrophylla), with a few trees growing even taller and forming the emergent layer, for example the Brazil-nut tree (Bertholletia excelsa). Many species have adapted to living in the trees of the canopy where food is abundant, including birds, bats, snakes and primates such as the white-handed gibbon (Hylobates lar).
Did you know? As well as tropical rainforests, there are also tropical dry forests. These are formed mostly of deciduous trees which shed their leaves to survive the long dry season. Although tropical dry forests typically support less biodiversity than rainforests, the fact that sunlight can reach the ground during the dry season means that a thick undergrowth layer can grow, providing plenty of food and shelter for ground-dwelling animals.
Found in north-eastern Asia, eastern North America and parts of Europe, temperate forests are characterised by having average temperatures of around 10 degrees Celsius and an average annual rainfall of between 76 and 152 centimetres. Unlike tropical rainforests, temperate forests go through four distinct seasons, with precipitation often falling as snow in the winter months. Temperate forests are many and varied, and while most contain a mixture of both deciduous and coniferous trees, one tree type typically tends to dominate.
In temperate deciduous forests, the dominant trees tend to be those with broad, flat leaves, such as maple (Acer species), birch (Betula species) and oak (Quercus species), and in the autumn the leaves of these trees change colour, creating a beautiful tableau of yellows, oranges and fiery reds. In the winter, the leaves drop to the nutrient-rich forest floor, which is covered in fertile soil and supports a range of shrubs, mosses, ferns and wildflowers. The presence of this abundant undergrowth in temperate forests means that, unlike in tropical rainforests, the majority of species can be found on the forest floor.
Temperate coniferous forests are typically found in coastal areas or inland mountainous zones, and have warm summers, relatively mild winters and tend to experience higher levels of precipitation than their deciduous counterparts. This moderate, moist climate allows for a long growing season, and so the dominant tree species in these forests, such as cedars (Cupressaceae family), pines (Pinus species) and firs (Abies species), can grow very tall, with enormous trees such as the giant sequoia (Sequoiadendron giganteum) of North America proving to be particularly impressive. The relatively slender, almost triangular shape of coniferous species makes the trees very strong and prevents the branches from snapping under the heavy weight of the winter snow. In contrast to the broad leaves of deciduous trees, the leaves of coniferous trees are either long, pointed needles or small, flat scales. These stay on the tree for several years, falling off gradually.
Animals living within temperate forest habitats have to adapt to the climate, with some species, such as the American black bear (Ursus americanus), coping with the cool winters by hibernating. Camouflage is another important adaptation for forest-dwelling species such as the adder (Vipera berus), which blends in well with its forest-floor environment. Although not as diverse as tropical rainforests, temperate forests still house an incredible array of species, from the industrious Eurasian beaver (Castor fiber) to the majestic bald eagle (Haliaeetus leucocephalus).
Did you know? You can tell the different types of coniferous trees apart by their needles - firs have short, blunt-tipped needles, while pines have needles that grow in bunches attached at the base, and spruces have very sharp, four-sided needles.
The northernmost forest type, boreal forests, or ‘taiga’, are characterised by short, moderately warm summers and long, cold winters, with a large proportion of the 40 to 100 centimetres of precipitation experienced each year falling as snow. The majority of boreal forests are found across Scandinavia and Russia, but this habitat type also occurs in Canada, Alaska and north-eastern Asia, typically between latitudes of 50 and 60 degrees North.
Boreal forest winters tend to be relatively dry, while summers are moist, and average annual temperatures are very low, ranging from about -5 to 5 degrees Celsius. Due to this cold climate, decomposition is very slow in boreal forests, resulting in thin, acidic and nutrient-poor soil.
The dominant trees in boreal forests tend to be coniferous species such as larch (Larix species), pine (Pinus species) and fir (Abies species) trees, although deciduous species such as white birch (Betula papyrifera) are also relatively common. The canopy of boreal forests tends to be rather dense, allowing little light to pass through, resulting in a limited understory and a fairly sparse forest floor covered in mosses and lichens. The growing season in boreal forests is short, typically lasting around three months, but the presence of moist ground in the summer as a result of snowmelt, in combination with long days, means that plant growth can be somewhat explosive.
Animal species found in boreal forests must be able to cope with extremely harsh conditions, and species such as the reindeer (Rangifer tarandus), snowshoe hare (Lepus americanus), grey wolf (Canis lupus) and bobcat (Lynx rufus) are all well adapted to their habitat, with thick fur helping them survive the long, cold winters. Boreal forests are also home to a number of fascinating bird species, including the spruce grouse (Dendragapus canadensis) and the great grey owl (Strix nebulosa).
Although sometimes considered to be a type of temperate forest, Mediterranean forests are typically found to the south of temperate regions, around the coasts of the Mediterranean, California, Chile, South Africa and Western Australia.
While the winters in Mediterranean forests are somewhat mild and wet, the summer months are typically hot and dry, and so many plant species living within these habitats have thick, leathery leaves to help them retain water in the intense heat. Special veins also help them to transport water when it rains, making the most of the little moisture available. Forest fires are a common occurrence in Mediterranean forest regions, and many plants living in these habitats are able to survive being scorched, with some even depending on fire to remove competitors and germinate their seeds. Mediterranean forests are characterised by short, broadleaf evergreen shrubs and oak trees, collectively known as ‘maquis’, and include the oak woodlands of California and the eucalyptus forests of Australia.
Many Mediterranean forest species are endemic, meaning that they are found nowhere else on Earth. A wide variety of charismatic species call Mediterranean forests home, including the Iberian lynx (Lynx pardinus), the Barbary macaque (Macaca sylvanus) and the Spanish imperial eagle (Aquila adalberti). These species have adapted to their habitat by being able to forage over large areas, whereas other Mediterranean forest species, such as the Mediterranean chameleon (Chamaeleo chamaeleon), have adapted by becoming agile climbers.
As well as being home to countless plants, animals and fungi, forests are extremely important to human wellbeing, providing vital ecological, economic, social and health benefits. More than 1.6 billion people around the globe depend on forests for their livelihoods, from the provision of food and clean air to preventing flooding and soil erosion.
Through the process of photosynthesis, trees and other plants produce life-giving oxygen, while also playing a role in battling climate change by acting as sinks for carbon dioxide. Incredibly, the amount of carbon stored within forests is currently greater than the amount of carbon in the atmosphere.
As well as providing food, shelter and jobs for forest-dependent populations, forests also stabilise the soil, preventing soil erosion and helping to regulate the potentially devastating impacts of storms and floods. Forests also feed our rivers, and even human populations living far from these habitats depend upon them, as they are vital in supplying the water for almost 50 percent of the world’s largest cities, including New York, Jakarta and Caracas.
Forests play an important role in supplying the raw materials that we use for all sorts of day-to-day products, such as paper, packaging and construction timber, and more than one quarter of modern medicines originate from tropical forest plants. Aside from the more obvious physical benefits of these diverse habitats, forests harbour great cultural and aesthetic value, and also contribute to the nature-based tourism industry.
Did you know? On average, a broadleaf tree can absorb around 10 kilograms of carbon dioxide per year.
Almost half of Europe’s land surface is covered in forest. However, after centuries of human influence, the vast majority of this forest is now classified as semi-natural.
The Atlantic forest lies along the east coast of South America, and is one of the most diverse and biologically rich forests in the world. Sadly, it is also one of the world’s most threatened ecosystems.
The eastern deciduous forest is a vast forest stretching along the eastern side of North America. Dominated by deciduous trees, it is composed of a diverse range of landscapes and ecosystems that vary in vegetation, soil and wildlife.
Wisconsin’s Northwoods are a beautifully diverse mosaic of forests, lakes, wetlands and bogs that blanket much of the northern part of the state of Wisconsin, in the United States.
Wytham Woods is a beautiful patchwork of deciduous woodland and grassland in the Upper Thames Basin in Oxfordshire, England. It is home to a range of plant species, and is carpeted by a stunning display of bluebells in spring.
Despite being vital to human livelihoods and the future of the world’s biodiversity, our forests are facing a range of threats and are being depleted at an alarming rate - in the last 50 years alone, at least 17 percent of the Amazon rainforest has been lost. Once a forest is destroyed, it can take a very long time for it to regenerate, particularly in boreal areas where the soil quality is poor and the climatic conditions are challenging.
In combination with unsustainable forestry practices, deforestation remains the greatest threat to the world’s forests, with logging, urban development and land conversion for agriculture all contributing to an annual loss of over 130,000 square kilometres of forest habitat globally — that equates to an area larger than the size of Portugal. In addition to losing their habitat to human development, some animal species living within forests are at risk of persecution and poaching as a result of coming into conflict with humans and their livestock. Species living within boreal forests are particularly sensitive to human disturbance.
In the Amazon, this deforestation leads to the release of almost half a billion tonnes of carbon each year, which contributes to the effects of climate change which in turn also have a negative impact upon forest habitats. Industrial and vehicular emissions cause acid rain and other forms of pollution, posing a serious risk to temperate deciduous and boreal forests in particular - over time the acid rain damages leaves, and causes plants to produce fewer and smaller seeds. The ability of plants to resist disease is also greatly reduced as a result of the presence of pollutants, leaving forests depleted and unhealthy.
Many of the world’s forests have existed for millions of years, and have always been exposed to forest fires, but the frequency of these has increased dramatically as a result of human activity. This has led to the direct destruction of forests, and in addition has contributed to increased carbon emissions from the burning wood. Forest fires are particularly frequent in the Mediterranean region, where a combination of threats has left many natural forest communities degraded or permanently altered. The accidental or deliberate introduction of invasive, non-native plants and animals can also have a devastating impact on forests, with the introduced species frequently out-competing the native species for important resources such as space and food.
Forests provide a whole host of benefits and products for humans, and while it is therefore unrealistic to stop all use of forest resources, it is important to ensure that forest management is carried out responsibly and sustainably. One way of doing this is through forest certification. If it is processed, transformed, manufactured and distributed in a sustainable way, wood and the products made from it can be officially labelled so that consumers can choose to purchase products derived from responsibly managed forests.
Reforestation, which involves the replanting or regeneration of forests which have been damaged or destroyed, is another key step which can be taken to counteract habitat loss. In some areas, forests are able to regenerate naturally, with seeds from nearby trees being dispersed by animals or the wind and becoming established in the deforested area. However, other areas need a helping hand, and native tree species need to be manually replanted. Reforestation is particularly helpful in creating ‘wildlife corridors’, which are stretches of habitat created to link isolated fragments of forest. There are a number of organisations around the world that aim to replant trees and help to regenerate and restore forest habitats.
The creation and maintenance of protected areas, such as nature reserves and national parks, plays a huge role in conserving both the biodiversity of forests and the benefits it provides. There are many organisations and commissions which focus on creating and safeguarding protected areas around the world, including IUCN’s Global Protected Areas Programme and the World Commission on Protected Areas. There are also various national and international laws and regulations in place to prevent the overexploitation of forest species, such as those listed on the Convention on International Trade in Endangered Species (CITES).
Understanding how forests work, including the ecology of forest-dwelling species, is vital to their conservation, and raising awareness of their plight is a big step towards saving forest habitats for future generations.
Find out more about forests and their conservation:
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Forests supported by...
Forests have been profiled with support from The Mitsubishi Corporation Fund for Europe and Africa to help raise awareness about the importance of forests and their distinctive biodiversity, and the need for their protection and conservation.
Teaching resources for 7-11 year olds:
Teaching resources for 11-14 year olds:
Thursday 15 February
The World's Favourite Unloved Species 2018 - the Galapagos Racer
Thursday 01 February
Thursday 01 February