Ecology of Fire-Dependent Ecosystems

Wildland Fire Science, Policy, and Management

Devan Allen McGranahan, Carissa L. Wonkka

• Editore: CRC Press
• Anno: 2020
• ISBN:
  9780429944932
• Edizione: 1
• Argomento: Biological Sciences
• Categoria: Ecology

Ecology of Fire-Dependent Ecosystems is brimming with intriguing ecological stories of how life has evolved with and diversified within the varied fire regimes that are experienced on earth. Moreover, the book places itself as a communication between students, fire scientists, and fire fighters, and each of these groups will find some familiar ground, and some challenging aspects in this text: something which ultimately will help to bring us closer together and enrich our different approaches to understanding and managing our changing planet.

-- Sally Archibald, Professor, University of the Witwatersrand, Johannesburg, South Africa

Most textbooks are as dry as kindling and about as much fun to sink your teeth into. This is not that kind of textbook. Devan Allen McGranahan and Carissa L. Wonkka have taken a complex topic and somehow managed to synthesize it into a comprehensive, yet digestible form. This is a book you can read cover to cover – I know, I did it. As a result, I took an enlightening journey through the history and fundamentals of fire and its role in the natural and human world, ending with a thoughtful review of the evolving relationship between humans and wildland fire.

-- Chris Helzer, Nebraska Director of Science, The Nature Conservancy, and author of The Prairie Ecologist blog

Ecology of Fire-Dependent Ecosystems: Wildland Fire Science, Policy, and Management is intended for use in upper-level courses in fire ecology and wildland fire management and as a reference for researchers, managers, and other professionals involved with wildland fire science, practice, and policy. The book helps guide students and scientists to design and conduct robust wildland fire research projects and critically interpret and apply fire science in any management, education, or policy situation. It emphasizes variability in wildland fire as an ecological regime and provides tools for students, researchers, and managers to assess and connect fire environment and fire behaviour to fire effects.

Fire has not only shaped social and ecological communities but pushed ecosystems beyond previous boundaries, yet understanding the nature and effects of fire as an ecological disturbance has been slow, hampered by the complexity of the dynamic interactions between vegetation and climate and the fear of the destruction fire can bring. This book will help those who study, manage, and use wildland fire to develop new answers and novel solutions, based on an understanding of how fire functions in natural and social environments. It reviews literature, synthesizes concepts, and identifies research gaps and policy needs. The text also explores the interaction of fire and human culture, demonstrating how fire policy can be made adaptable to cultural and socio-ecological objectives.

CHAPTER 1

Introduction

Fire has flourished on Earth for nearly 500 million years. Fire began with the origin of terrestrial vegetation, which provided two critical components: fuel, and atmospheric oxygen. Although fire appeared in various forms through the eons, the nature of fire consisted generally of a simple chemical reaction turning plant material and oxygen into heat, light, and gasses whenever a spark was introduced to a sufficient amount of dry vegetation.

Humans transformed fire into a phenomenon. Fire not only shaped communities but pushed ecosystems beyond previous boundaries; fire cooked food and stoked cultures; and now, fire has altered the atmosphere that brought it into being. As human capacity to understand the Earth system developed, so too did understanding of fire chemistry and physics. But understanding the nature and effects of fire as an ecological disturbance has been slower, hampered by the complexity of the dynamic interactions between vegetation and climate and by fear of the destruction fire can bring.

We intend for this book to help those who study, manage, and use wildland fire to develop new answers and novel solutions, based on an understanding of how fire functions in natural and social environments. We review literature, synthesise concepts, and identify research gaps and policy needs. We seek to help readers develop the knowledge base to design and conduct robust wildland fire research projects and critically interpret and apply fire science in any management, education, or policy situation.

A BRIEF HISTORY OF FIRE IN THE EARTH SYSTEM

Fire historian Stephen Pyne defined Three Fires to describe the progression of fire on Earth:

• First Fire—natural burning in an oxygen-rich atmosphere, which shaped today's geographical distribution of species and ecosystems.
• Second Fire—anthropogenic fire, when humans learned to use fire for their advantage. Long periods of intentional human burning affect ecological structure and composition today, and humans still use Second Fire for the same reasons as their ancestors.
• Third Fire—industrialised fire, when fire moved into novel habitats like furnaces, engines, and bombs. In Third Fire, fire went from simply combining vegetation, heat, and oxygen to the exploitation of concentrated, high-energy fossil fuels, whose byproducts will affect the distribution and composition of life on Earth into the future.

Natural burning

The history of fire on Earth is limited to what can be reconstructed from the geologic record. Evidence consists largely of fossilised charcoal, called fusian (Fig. 1.1), and other charcoal deposits found in sedimentary layers.

James St. John CC BY 2.0

Figure 1.1: Fusian is fossilised charcoal, apparent here in a chunk of weathered coal from the Middle Pennsylvanian, found in Ohio, USA.

Earth was probably fire-free until ca. 400 million years ago, prior to which fire was impossible without two major components: fuel and oxygen. The evolution and global spread of terrestrial plants addressed both issues, providing vegetation biomass for fuel and oxygen as a byproduct of photosynthesis, which then accumulated to levels in the atmosphere sufficient for combustion. The first fusian records date to the late Devonian, just before substantial deposits from the beginning of the Carboniferous period (Scott 2000). Alternating periods of fire activity and inactivity generally track fluctuations in atmospheric oxygen levels (Pausas & Keeley 2009).

Fire was among the dynamic ecosystem processes that changed in response to major shifts in climate worldwide throughout the Quaternary period, which began nearly 3 million years ago and continues through the present. There is considerable evidence of fire from the Quaternary period in the geologic record. Fire histories can be inferred from biological clues into broad climate and ecosystem patterns such as pollen cores taken from the bottom of ancient lakes and isotopic ratios of fossilised creatures like mollusks. Many of these records point to dramatic but cyclical variability in plant community composition, with concurrent variability in the frequency and type of fires through the pre-modern epoch known as the Pleistocene.

The Pleistocene shaped the current distribution of species, ecosystems, and processes. Climatic variation during the Pleistocene was driven by waxing and waning glaciers, which were so prevalent that the Pleistocene is commonly known as the Ice Age. During periods of glacial maxima, Earth's water was bound up as ice, sea levels dropped, and global climate became arid. Under these conditions, grasslands and savannas spread worldwide. The forests that dominated the early Eocene slowly opened up as the climate warmed and dried. Through the Miocene and Pliocene, grasses adapted to a warmer, drier climate, and fire drove their evolution and spread (Hoetzel et al. 2013, Scheiter et al. 2012). By the Pleistocene, grass-dominated, fire-prone ecosystems characterised much of Earth's terrestrial surface not covered by ice. It is likely that by evolving fire-tolerant traits grasses themselves promoted fire, and as if playing leap-frog, fire-adapted grasslands and fire itself made incursions into areas long held by forests.

Anthropogenic burning

Another consequential product of the Pleistocene was humans—humans who used and promoted fire as they followed the worldwide spread of grasslands and savannas. While many animals have adapted to fire, humans are unique in having captured fire and put it to work for them. Fire played a central role as human culture and technology developed, and humans applied novel uses of fire everywhere they settled. Since the Pleistocene, anthropogenic fire has modified landscapes worldwide, although changes are tempered by the local biota and human culture.

The archaeological record cannot say how early hominins interacted with natural fire, but primates today suggest it was calm and utilitarian. In the field, chimpanzees respond to grass fires as part of their daily adventure: a lookout climbs a tree and vocalises to others before they file through the flame front at a point with low fuels and small flames (e.g., Pruetz & LaDuke 2010). And in the laboratory, great apes prefer cooked food (Wobber et al. 2008). It is easy to imagine how early hominins engaged natural fire and brought it back to the hearth (Gowlett & Wrangham 2013).

Domesticated fire both served and catalysed human culture. The human brain developed for social interaction, and after the light of the workday waned, humans gathered around fires for storytelling and communal bonding (Dunbar 2014). In extant Stone Age cultures like those of the Kalahari (Fig. 1.2), night-time conversation shifts towards stories, songs, and religious ceremonies, and is conducted around the fire (Wiessner 2014).

Ian Sewell CC BY-SA 2.5

Figure 1.2: Two San men in Botswana start a fire by hand. Anthropological research of extant hunter-gatherer cultures provides insight into how prehistoric humans made use of fire.

Humans probably first burned landscapes for the convenience of stimulating wild food production and attracting game. Intentionality in fire use developed into what is now known as “fire-stick farming” (Jones 1969), which predated the sedentary Neolithic agriculture that persists in indigenous agroforestry practices worldwide: deliberate, low-intensity fires remain components of tropical home garden traditions and Australian Aboriginal culture today (Nigh 2008). In the tropics, swidden agriculture—or, colloquially, “slash and burn”—relied on fire to clear early-succession vegetation and restore soil fertility after deliberate fallow periods (Fig. 1.3). In Europe, fire was similarly used to clear land and manage field stubble (Fig. 1.4).

Alzenir Ferreira de Souza CC0

Figure 1.3: Tropical agriculture worldwide continues to use fire to clear fallow land in preparation for planting. Fire clears vegetation and increases soil nutrient levels, at least temporarily.

public domain

Figure 1.4: A 19^th-century print by Berndt Lindholm (1841–1914) depicts burning to clear land in Iisalmi, Finland.

Industrialised fire

Third Fire ignited the Industrial Revolution by unlocking fossil fuels like coal, natural gas, and oil—the mineralised remnants of biomass that escaped First Fire in the Carboniferous period. Millions of years of geologic pressure turned lignin into lignite, which fueled dense cities and productive ...

Indice dei contenuti

• Cover
• Half Title
• Title Page
• Copyright Page
• Dedication
• Contents
• Foreword
• Chapter 1 Introduction
• Section I Fire Fundamentals
• Section II Fire Effects
• Section III Human Dimensions
• About the authors
• References cited
• Image attributions
• List of Tables
• Index