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There are important social-developmental contributions to the acquisition of flexible, generative, context-sensitive thinking and engagement with the world. We highlight how among individuals with autism, limitations in the propensity to identify with the attitudes of other people might lead to a paucity of movement across alternative ‘takes’ on the world, and with this, specific forms of cognitive restriction and rigidity.
Consider this condensed version of a classic description of a person with autism called L (Scheerer et al. 1945). L was first seen at the age of 11 with a history of severe learning difficulties. He was said never to have shown interest in his social surroundings. Although he had an IQ of only 50 on a standardised test of intelligence, L could recount the day and date of his first visit to a place, and could usually give the names and birthdays of all the people he met there. He could spell forwards and backwards.
L's background history included the fact that in his fourth and fifth years he rarely offered spontaneous observations or reasons for any actions or perceived event. Nor would he imitate an action of others spontaneously. He was unable to understand or create an imaginary situation. He did not play with toys, nor did he show any conception of make-believe games. He was unable to converse in give-and-take language. He barely noticed the presence of other children, and was said to have ‘little emotionality of normal depth and coherence’.
Year after year pictures in the media show towering flames threatening people's homes, livelihoods, and their very lives in places as diverse as North America, Europe and Australia – why does this happen? Conflicting stories continually appear over whether fire is rapidly destroying the animals, habitats and plants we treasure in our forests, or whether fire is their salvation, the key to diversity and ecosystem rebirth – where does the truth lie? With global warming predictions, do we face more and larger fires or will technology be able to tame this potentially savage enemy? This book delves into these and other questions, providing a factual account and perspective of how fire burns in the forest, what it does and how it might be controlled.
Where the published work of others is used, or where good sources of extra information are recommended, the authors and the date of the publication are given so that the source can be found in the references at the end of the book. This inevitably has resulted in a compromise; we've tried to keep this to a minimum to help the text flow but give sufficient references to help the reader who wishes to find out more. Our apologies if we fail you at any point.
How destructive or beneficial are forest fires to wildlife? Should we be trying to reduce or increase the amount of fire in forests? How are forest fires controlled, and why does this sometimes fail? What effect will climate change have? These and many other questions are answered in this richly illustrated book, written in non-technical language. The journey starts in the long geological history of fire leading up to our present love-hate relationship with it. Exploring the physics of how a single flame burns, the journey continues through how whole forests burn and the anatomy of firestorms. The positive and negative ecological effects of fires are explored, from plants and wildlife to whole landscapes. The journey ends with how fires are controlled, and a look to the future. This book will be of interest to ecologists, biogeographers and anyone with an interest in forest fires and the role they play.
The region within the European Union classified in the Habitats Directive under category 90 ‘Forests of Boreal Europe’ is but a fraction of an immense biogeographical zone that stretches east, covering over 700 million hectares of Siberia, and that continues on in a vast swathe through northern North America and Canada. Russia alone supports 22% of the world's forests and between 70–75% of this area remains close to natural. The ‘Taiga’, as it is also known, is large in nearly all senses of the word; the size of habitats, including mires, lakes and rivers that nest within it; the large, roaming herds of big game; the size of the big animals, including moose and brown bear; and not least of all, the scale of disturbances and processes that give this ecosystem its distinctive character. To most who know it, the boreal biome remains one of the last frontiers of wilderness, a ‘self-willed’ land shaped by the forces of wind, snow, pathogens, herbivores and especially fire.
South of the equator, on the African continent, stretching 2500 km from east to west and 1250 km north to south, lies one of the greatest expanses of uniform vegetation in Africa, the Miombo Forest. This landscape of trees and grass, sometimes dense uniform forest, is dominated by trees belonging to the genera Brachystegia and Julbernadia.
The previous chapter explains how a fire burns and what types of fire are possible. But once out in the real world there are many influences that determine whether a fire starts and how it subsequently behaves. First of all, there has to be a source of ignition – the spark or heat source intense enough to cause combustion – and this has to coincide with some sort of flammable material in a dry enough state to burn. Once the fire has started, its behaviour in terms of how fast and far it will spread and how much energy it produces is primarily controlled by the weather, the shape of the terrain (topography) and the amount and state of the fuel. These three factors can be fitted together as a fire behaviour triangle (see Fig. 4.5); change one side of the triangle and the fire regime will also change, often dramatically. Which one of these factors is most important in shaping the fire of an area will vary depending on the region, the ecosystem type and historical events such as previous fires.
The fire regime of an area can be defined as the characteristic frequency, extent, intensity and seasonality of fires within an area. You should also be aware that the fire itself can influence the weather and fuel sides of the triangle and hence the fire regime – it is a two-way process.
Prior to the arrival of humans, fires came and went, the forest grew, burnt, and regrew. Fire was a systematic, natural process within many ecosystems. With the arrival of early humans, fire became more prevalent on the landscape (with the new fire starters), and the ecosystem adapted to the changing regime. It is only in the last 100 years or so that humans have found the need to systematically suppress fire and attempt to eliminate its destructive nature – essentially to tame it. Suppression activities began in earnest after World War II when aeroplanes, helicopters, smokejumpers and new firefighting strategies were introduced. Why have we attempted to remove this element of the ecosystem from its natural role? The answer is simple, of course – fire competes with us for natural resources, fire threatens and destroys our property and it can kill. In many parts of our world, the economy is dependent on the renewable resources found in the forest. Our lives and lifestyles also depend on homes, buildings, telecommunication towers and lines, pipelines and a host of other infrastructure elements in and around wildlands (natural or semi-natural forest) at risk of fire. The normal feeling is that fire cannot be allowed to threaten and disrupt our lives and economy. The existence and mission of fire suppression is thus based on the protection of human life, property and the resources upon which economies depend.
Fire is a chemical reaction that results in the very rapid release of the energy stored in fuel. Plants use the sun's energy to combine carbon dioxide with water to produce carbon compounds (sugars, starch, cellulose etc.) and oxygen. When a plant dies and decomposes, the reverse happens: oxygen is used up in breaking apart the carbon compounds to release carbon dioxide, water and a gentle trickle of heat (think about the heat produced by a good rotting compost heap or pile of manure). Fire is a form of decomposition, just a lot quicker, releasing the carbon dioxide, water and heat in a massive burst. In this chapter we start at the beginning and look at how plant material burns before considering how a whole fire burns.
Mechanics of fire
When heat is applied to, for example, a piece of wood, three distinct phases are passed through: pre-ignition, ignition and then combustion.
When heat is first applied to our piece of wood, the energy will initially be absorbed by water contained in the wood (which has a large capacity to store heat). Then as the temperature rises further (Fig. 3.1a), the heat evaporates the water at the surface of the wood (it may even steam as the water vapour condenses in the air) which keeps the wood surface around 100 °C (see Box 3.1 for a demonstration of this).
In 1899 Gifford Pinchot, who in 1905 became the first Chief of the United States Forest Service (USFS), wrote an article for National Geographic magazine entitled ‘The relation of forests and forest fires’ in which he stated, ‘That fires do vast harm we know already, although just what the destruction of its forests will cost the nation is still unknown.’ Influenced by European views of forestry and founded on the belief of human mastery over nature, the passionate and charismatic Pinchot, along with his understudies and eventual successors, led a crusade against fire that was considered both morally acceptable and economically desirable. Forests, like other natural resources, were deemed valuable assets to be used to meet immediate human needs and increase the wealth of those who owned them. Pinchot's conservationist vision ‘to control the use of the earth and all that therein is’ (Cortner & Moote 1999) was confidently thought to be not only plausible but completely possible owing to an era of tremendous optimism in western society at that time. Reaping the benefits of the industrial revolution, including the steam engine, electricity and the telephone, human progress was fuelled by a philosophy of scientific determinism that viewed the world and how it functioned as orderly, machine-like, and therefore predictable as well as controllable. The famous author H.G. Wells captured this sentiment in 1902 in his address at the Royal Institution of Great Britain suggesting that if humans were to channel the same level of scientific effort on the future as had been placed on understanding the past it would be possible to predict what lies ahead with certainty.
When considering forest fires and the survival of plants and animals there is a glaring paradoxical imbalance. A flame has a temperature of around 800–1200 °C whether it is the gentle flame of a match or candle, or a raging forest fire (see Chapter 3 for a longer discussion), and physiologically active living tissue (plant or animal) is killed by a short exposure to temperatures above 50–60 °C.
A burning forest does not consist of solid flame, so inevitably the temperature inside the forest is not uniformly that of a burning flame. Hot air rises, dragging in colder air near the ground from the sides. Thus although the centre and top of a burning canopy may be above 1000 °C, temperatures may be expected to reduce with height to perhaps just a few hundred degrees, unless there is a marked radiation of heat downwards from burning fuel above ground level (such as in dense shrubbery). Even so, temperatures above 100 °C may persist for up to several minutes near the ground, especially if the ‘burnout time’ is long (see Box 5.1). The main key to surviving forest fires is to keep the heat of the flame away from living tissue. How this is done very much depends on whether you are considering plants or animals, and if looking at plants, what sort of fire is burning – whether it is a ground fire, a surface fire or a crown fire. Some plants will also continue via seeds if the parent is killed.
Welcome to Fire in the Forest. The ancient Greeks considered fire as one of the classical elemental forces along with water, earth and air; and indeed fire has helped shape the world around us to such a great extent that it would be hard to argue the point. Without a doubt, there is nothing on this planet that cannot be traced back (many times over) to some kind of fiery origin, whether that be the Big Bang at the origin of the universe, the atomic fires of some long dead pre-supernova star, the liquid burning rock just below the crust of the earth or the vegetation sitting frailly on the surface of the planet. While all of these forging fires are fascinating, a tome that spans the fullness of fire would be many volumes thick. The focus of this book is to explore the various facets of fires in forests: from how a single flame works, to what determines whether a forest will burn, to why huge forest fires occur and how they can be tackled. In this we will be dealing primarily with wildland fires – fires in the natural or semi-natural forest rather than those in plantations or in urban areas. These wildland fires have shaped the planet's biotic structure so we also focus on how plants and animals cope with fire, our own interaction with fire and ultimately our overall relationship with the whole planet.