Forest fires research

Forest fires research: beyond burnt area statistics

Editors Jorge H. Amorim, J. Jacob Keizer, Ana I. Miranda, and Kieran Monaghan

Title Forest fires research: beyond burnt area statistics Editors Amorim J.H., Keizer J.J., Miranda A.I., Monaghan K. Graphic Design Jorge H. Amorim 1st Edition July 2011 Number of copies 100 Copyright xxxxx ISBN xxxxxx

Index 1

Foreword ....................................................................................................................1

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Fire-Related Research at the A ssociate Laboratory CESAM ......................................3

Pre-fire 3

Managing Forests for Increased Fire Resilience ........................................................7 3.1 Introduction ..........................................................................................................7 3.2 Fuel management and fuel treatments ...................................................................7 3.3 Different forest types, different fires .......................................................................9 3.4 Conclusion ......................................................................................................... 10 Referenc es .................................................................................................................... 11 4 Fire in the Amazon Forest ........................................................................................ 13 4.1 Introduction ........................................................................................................ 13 4.2 Deforestation and biomass burning...................................................................... 14 4.3 Emission factors for combustion gases in Amazonian burns .................................. 16 4.4 Forest fragment ation and vulnerability to understory fires ...................................... 16 4.5 Conclusions ....................................................................................................... 17 Referenc es .................................................................................................................... 18

During fire 5

Forest Fire Behaviour ............................................................................................... 21 5.1 Introduction ........................................................................................................ 21 5.2 General aspects of fire behaviour modeling .......................................................... 21 5.3 Dynamic fire behaviour ....................................................................................... 22 5.4 Fire behaviour and fire safety .............................................................................. 24 5.5 Conclusion ......................................................................................................... 25 Referenc es .................................................................................................................... 26

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Forest Fire Emi ssions............................................................................................... 27 6.1 Introduction ........................................................................................................ 27 6.2 Methodology ...................................................................................................... 27 6.3 Results and Discussion....................................................................................... 29 6.4 Conclusions ....................................................................................................... 31 Referenc es .................................................................................................................... 32

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Forest Fires, Air Quality and Human Exposure ........................................................ 33 7.1 Introduction ........................................................................................................ 33 7.2 2003 forest fires impact on air quality ................................................................... 33 7.3 Forest fires and fire-fighters exposure to air pollutants .......................................... 37 7.4 Conclusions ....................................................................................................... 37 Referenc es .................................................................................................................... 38

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Baseline Measurement of Smoke Exposure Among Wildland Firefighters ............... 39 8.1 Introduction ........................................................................................................ 39 8.2 Methods ............................................................................................................. 39 8.3 Results .............................................................................................................. 41 8.4 Discussion ......................................................................................................... 42 Referenc es .................................................................................................................... 44

Post-fire 9

The Effects of Wildfire on the Biosphere .................................................................. 47 9.1 Introduction ........................................................................................................ 47 9.2 Terrestrial systems ............................................................................................. 48 9.3 Aquatic systems ................................................................................................. 49 9.4 Conclusions ....................................................................................................... 52 Referenc es .................................................................................................................... 52 10 Fire Effects on Soil and Water Resources, and their Mitigation................................ 53 10.1 Introduction ........................................................................................................ 53 10.2 Background........................................................................................................ 53 10.3 Hydrological and associated transport processes in recently burnt areas ................ 54 10.4 Land-use policies and stakeholders’ involvement in their implementation ............... 56 Referenc es .................................................................................................................... 57 11 Planning Post-fire Restoration ................................................................................. 59 11.1 Introduction ........................................................................................................ 59 11.2 Ecological restoration strategy in Mediterranean fire-prone ecosystems and landscapes..................................................................................................................... 60 11.3 Perspectives ...................................................................................................... 63 Referenc es .................................................................................................................... 63

Fire in the future 12

Fire Activity Under Future Climate ........................................................................... 67 12.1 Introduction ........................................................................................................ 67 12.2 Fire activity, weather and the FWI........................................................................ 68 12.3 Climate change impacts on area burned and forest fire occurrenc es ...................... 70 Referenc es .................................................................................................................... 71 13 Erosion Under Future Fire Scenarios ....................................................................... 73 13.1 Introduction ........................................................................................................ 73 13.2 Problem statement ............................................................................................. 73 13.3 Study area ......................................................................................................... 75 13.4 Challenges ......................................................................................................... 76 13.5 Adapting erosion models to post-fire contributions ................................................ 76 13.6 Back-casting erosion bet ween 2002 and 2010 ...................................................... 77 13.7 Future climate research strategy.......................................................................... 78 Referenc es .................................................................................................................... 78

1 Foreword Jorge H. Amorim, J. Jacob Keizer, Ana I. Miranda, and Kieran Monaghan (Editors) CESAM, University of Aveiro Aveiro, 3810-193, Portugal e-mail contacts: [email protected], [email protected], [email protected], [email protected]

During the last few years extreme fire occurrences in distant parts of the globe such as Australia, Russia and United States of America (USA) have increased global awareness and concern about the destructive power and profound consequences of forest fires. The complexity and extent of the impacts of forest fires, however, go far beyond the statistics provided by official reports and media on, for example, total burnt area, number of destroyed houses, or human casualties. The World Health Organization (WHO, 2007) has identified forest fires, and particularly those occurring close to urban areas, as one of the major threats to public health security in the 21st century, stressing the need for politicians, experts and stakeholders to recognize the magnitude and multidimensionality of the impacts of forest fires and the resulting risks. The WHO has also alerted that effective measures of risk and crisis management are urgently needed. Intended to promote a more interdisciplinary approach to the multiple and interrelated factors influencing and potentiating the occurrence, severity and impacts of forest fires, the Centre for Environmental and Marine Studies (CESAM) organized an International Workshop entitled “Forest fires research - beyond burnt area statistics”. On May 26 2010 at the University of Aveiro, it brought together a variety of experts, professionals and students from Portugal, Spain and the USA. This booklet aims to share the main contents of the presentations that were given by national and international scientists during the workshop. It is organised according to four different stages in relation to the occurrence of forest fires: before, during, after and under future conditions. The different chapters address a wide range of distinct but clearly interrelated research topics, namely: fire prevention; fuel management; fire behaviour and suppression; smoke emissions, air pollution and human exposure; ecosystem functioning and biodiversity; hydrology and soil erosion; ecological restoration; ecotoxicology; socio-economic factors; and climate change impacts.

WHO, 2007. The w orld health report 2007 - A safer future: global public health security in the 21 st century. World Health Organization (WHO). Geneva, Sw itzerland. 72 pp.

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2 Fire-Related Research at the Associate Laboratory CESAM Casimiro Pio Director of CESAM, University of Aveiro Aveiro, 3810-193, Portugal e-mail contact: [email protected]

Population growth and associated anthropogenic activities have caused changes to the planet over a range of different fields, including environmental contamination, resource depletion, declines in biodiversity and climate change. The 2007 Intergovernmental Panel on Climate Change (IPCC) report predicts that Mediterranean regions will be amongst the areas most impacted by climate change, with a substantial increase in temperature and a decrease in rainfall. The predicted increases in extreme events such as heat waves and periods of prolonged drought will impose additional stress on ecosystems and society, resulting for example in enhanced deficits in water supply and increases in the frequency and intensity of forest fires. Wildfires have always existed in nature and are, under natural conditions, a mechanism for renewal and ecosystem balance. However, forests in present-day southern Europe are, to a large extent, man-made, so that forest fires become highly detrimental not only in terms of the environment and public health but also of the economy. The dimension of the wildfire problem at present and the expected evolution of environmental conditions towards facilitating the onset and spread of fires emphasize the urgent need for the development and implementation of strategies at various organizational levels , ranging from fire prevention to combat and remediation across Mediterranean regions and in Portugal in particular. To apply appropriate, economically and environmentally sustainable strategies, the phenomenon of wildfires and their consequences need to be studied scientifically. For decades, research activity in Portugal has been limited in all scientific areas, including that of forest fire. The scientific production related to this topic (including burning of forest biomass), as reflected by output in research journals, has been somewhat limited, with approximately 180 published articles listed in the ISI web of knowledge. In recent years, however, and in line with an overall increase in research activity in Portugal, there has been a marked growth of research activities in the area of forest fires, and the majority of the afore-said articles (110) have been published in the last five years. The University of Aveiro has contributed significantly to this trend, contributing with around 24% to the national output in the years prior to 2005 vs. 33% in the last five years. Thus, at present, one third of the Portuguese papers in the topic of forest fires is (co-)authored by the University of Aveiro, most of which are produced by researchers from CESAM. CESAM is one of the research units of the University of Aveiro; it has the status of Associate Laboratory

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and has as overall mission to study the marine and coastal environmental systems. Environmental research at CESAM is conducted from an inter-disciplinary perspective, incorporating the biological, physical, chemical and geological processes and their interaction with society. Founded in 2002 as a continuation of the Centre of the Coastal Zones and the Sea (CZCM), CESAM has achieved a sustained growth, as reflected by the number of researchers, currently amounting to 150 doctoral researchers and 200 PhD students, as well as by the number of funded research projects, conferred doctorate degrees, publications and citations. The five scientific disciplines underpinning research at CESAM allow to address the various and complementary aspects of forest fires. This, combined with the experience accumulated in recent years and the existence of a team of young and motivated researchers, positions CESAM in a favourable situation to continue developing high-quality, fundamental and applied research in this area that is so important for the country and where there remains so much scope for further understanding. Within the theme of forest fires, CESAM researchers have developed research on a marked variety of topics that include: 

Modelling the prediction, evolution and suppression of fires;



Composition and emissions of pollutants into the atmosphere;



Transport and atmospheric dispersion of plumes;

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Modelling the effects of forest fires in the photochemical pollution;



Effects on health;



Effects on hydrology, erosion and soil quality;

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Impact on surface water quality;

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Impact on biodiversity of terrestrial and aquatic ecosystems;

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Effect on the carbon cycle;

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Fire scenarios under future climate change;



Domestic and industrial burning of forest biomass.

Currently, CESAM has a total of 40 researchers dedicating their efforts to the study of forest fires, mostly on issues related to the fires’ consequences. A substantial part of these researchers, approximately 25%, is studying processes that occur during forest fires or forecasting future scenarios of fire risk. Fire prevention, by contrast, has received comparatively little research attention at CESAM. The fire-related studies are spread over approximately 30 research projects funded at both the European and national level. The directors and researchers of CESAM have been working to expand and deepen their work on Portuguese forest fires, trying to develop and evolve the various scientific branches within our organization, in collaboration with researchers and research groups from national and international scientific institutions. This workshop, organized by CESAM’s young researchers, represents one more step in this direction, aiming at furthering the scientific knowledge that is so fundamental for the sustainability of our planet in these difficult and challenging times.

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pre-fire

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3 Managing Forests for Increased Fire Resilience Paulo M. Fernandes* Centro de Investigação e de Tecnologias Agro-Ambientais e Biológicas (CITAB), Universidade de Trás-os-Montes e Alto Douro * Corresponding author e-mail: [email protected]

3.1

Introduction

The Mediterranean Forest Research Agenda (EFI, 2010) is useful as a framework to describe our current goals of wildland fire research. Short-term fire control policies should give the way to “longer-term policies aimed at acting on the structural causes of fires and integrating fire and forest management strategies”. Consequently, fire research priorities should include landscapescale issues related to large fires, fire severity mitigation in forest stands, and which forest types are less fire-prone and more fire-resilient. The relevance of these topics is further emphasized by climate changes, because the expected increase in fire danger will raise burned area and carbon emissions (Thonicke et al., 2010). Mediterranean forests will adapt to climate change with difficulty and it has been recognized by the IPCC that their protection from wildfire will be important, including through large-scale fuel management with prescribed burning (Parry et al., 2007). Forest management towards higher resistance to fire spread and improved fire resilience consists of two complementary approaches, respectively the treatment of fuels in fire-prone vegetation types and the modification of forest type. Here an overview and some results illustrating recent and on-going research initiatives on these topics will be provided.

3.2

Fuel management and fuel treatments

Learning with wildfires, experimenting with fire or using simulation tools are the three basic approaches to fuel management research. To what extent is wildfire incidence controlled by fuel? This should be the first question in relation to the relevance and effectiveness of fuel management. Although the answer to this question differs with vegetation type, it is generally accepted that high-intensity fire regimes are driven primarily by weather. In Portugal t he median fire-free interval is relatively short (12-16 years) but the re-burn probability (hazard) of a given area grows exponentially with time since fire, as the aging of fuels results in fuel accumulation and higher flammability (Figure 3.1; Fernandes et al., 2010a). Furthermore, it seems that this time-dependency of fire incidence is only marginally affected by extreme weather. Fire size and maximum fire size tend respectively to be less variable and lower where fire recurrence is higher. Hence, the control of fuels over landscape fire spread occurs on a relatively short-term scale but is effective, thus supporting a prominent role of fuel treatments in fire management.

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Figure 3.1 – Empirical probability of fire occurrence (a) and Weibull hazard of burning (b) for the N-CE and CW-S subdivisions of Portugal (Fernandes et al., 2010a).

The study of fire-resistant forest stands, i.e. exhibiting some degree of post-fire tree survival and/or fire severity mitigation, can inform technical guidelines for stand management against wildfire. The existing silvicultural recommendations often are of uncertain origin and not supported by theory or sound empirical evidence. Pinus pinaster patches surviving wildfires in northern Portugal exhibit size-dependent tree mortality, and are able to persist under a regime of frequent fires, which promotes more open and vertically discontinuous stands (Figure 3.2; Vega et al., 2010). These fire-resistant structures can be used as a silvicultural model for fuelbreaks and other fuel-treated areas. Additionally, the observed variability in stand structure and maintenance of regeneration indicate resilience to fire.

Figure 3.2 – Fire-resistant Pinus pinaster stand in Portugal, w ith tree density = 250 ha-1, basal area = 11 m2 ha-1 and median fire return interval = 6 years.

Experimental studies of fire behaviour and effects have important applications in the evaluation and planning of fuel treatments. Fire modelling allows simulation of fire characteristics for different fuel and stand management scenarios (e.g. Cruz et al., 2008) as well as landscapelevel analysis of fire-spread potential in response to variation in fuels and other factors (e.g. Loureiro et al., 2006). However, direct empirical evidence of the differences in fire behaviour and severity between alternative fuel treatments or between treated and untreated stands can only be obtained from the real world. Wildfire data are valuable but anecdotal, and experimental

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fires on this topic have been extremely scarce worldwide. Under a fire danger rating of Very High, we have observed a drastic change in fire behaviour — from crowning to relatively mild surface fire — when the fire moved from an untreated 28-year old stand to areas treated with prescribed fire 2-3 years before (Fernandes et al., 2004); differences in fire characteristics between 13- and 28-year fuel accumulation could not be proven because of fluctuations in wind speed and direction. However, analysis of related data has indicated lower surface fire intensity in prescribed burnt plots for at least 10 years after treatment (Fernandes, 2009a), due to the persistence of lower shrub and litter loadings in the treated plots.

3.3

Different forest types, different fires

Forests with different species compositions can have distinct fire potential, as an outcome of differences in the nature, quantity and arrangement of fuels. Because stand structure affects both the fuel-complex and the local weather environment (fuel moisture, wind speed), it can offset the effect of cover type to a certain degree, as was shown in the simulation study of Fernandes (2009b), where the range in fire hazard was similar between and within cover types. Potential fire risk increased in the following order: (1) open and tall forest types, and closed and tall Quercus suber and diverse forests; (2) closed, low woodlands of deciduous oaks, Q. suber and diverse forests, closed and tall Pinus pinaster woodland and tall Eucalyptus globulus plantations; (3) open and low forest types; (4) dense low stands of P. pinaster, E. globulus and Acacia spp. If fire modelling takes into account the spatial variation in fuels and stand structure, gradients in fire behaviour can be described in the transition of one vegetation type to another, e.g. shrubland to Quercus rotundifolia forest patches (Azevedo et al., 2009). It is conventional wisdom among forest researchers and managers that some forest types, namely deciduous broadleaves, are effective at modifying fire behaviour and disrupting landscape fire spread. Fire modelling (Fernandes, 2009b) and fire selectivity (e.g. Moreira et al., 2009) studies support this hypothesis. However, the fire severity implications of cover type changes are not well understood. Fernandes et al. (2010b) compare fire severity between adjacent stands of P. pinaster and of other species (deciduous and evergreen broadleaves and short-needled conifers) in northern Portugal. Fire intensity inferred from stem char height (adjusted for the effects of other factors) was highest in P. pinaster, followed by deciduous broadleaved and short-needled conifer forest. In addition to cover type, fire severity was explained by stand characteristics (height, density, basal area), aspect, fire spread pattern and distance to the edge between P. pinaster and the contiguous cover type. A faster decline in fire severity was observed in deciduous broadleaves, and fire severity tended to decrease with stand maturity and under moister conditions. Implicit in these results is the fact that different cover types will not be different just in their fuel complexes. Simultaneous measurements of micrometeorological

variables

and fuel

moisture contents

will

highlight

weather-related

differences in the fire environment between forest types, provided that the stands are adjacent and do not differ in aspect and slope (Figure 3.3).

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Figure 3.3 – Simultaneous measurement of relative humidity in tw o nearby stands of Pinus pinaster and Betula alba under identical topographical position. Higher values tend to be observed in Betula, a mesic deciduous type.

The results indicate that less fire-prone landscapes would result from expanding broadleaved forest or mountain conifers. However, fire severity refers to the immediate impact of fire and is not synonymous with fire resilience. It is the interaction between fire severity and species traits (related with post-fire response) that will dictate fire resilience. Consequently, research on post fire tree mortality patterns is an important supplement to fire severity studies. The description and prediction of fire-induced mortality to southern European tree species has recently gained momentum, covering the entire fire severity range and addressing both conifers (P. pinaster (Figure 3.4); P. nigra) and broadleaved species (Quercus spp., Castanea sativa, Eucalyptus globulus) (Moreira et al., 2007, Fernandes et al., 2008, Catry et al., 2010, Vega et al., 2010). RSH

≥0.9