In: Chuvieco E. (ed.) Remote sensing of large wildfires in the European
Mediterranean basin, pp.3-16. Springer-Verlag, 1999.
2 The role of fire in European Mediterranean
Ecosystems
Juli G. Pausas and V. Ramon Vallejo
Centro de Estudios Ambientales del Mediterráneo (CEAM)
Abstract. Fire is an integral part of many ecosystems, including the
Mediterranean ones. However, in recent decades the general trend in number of
fires and surface burnt in European Mediterranean areas has increased
spectacularly. This increase is due to: (a) land-use changes (rural depopulation is
increasing land abandonment and consequently, fuel accumulation); and, (b)
climatic warming (which is reducing fuel humidity and increasing fire risk and fire
spread). The main effects of fire on soils are: loss of nutrients during burning and
increased risk of erosion after burning. The latter is in fact related to the
regeneration traits of the previous vegetation and to the environmental conditions.
The principal regeneration traits of plants are: capacity to resprout after fire and
fire-stimulation of the establishment of new individuals. These two traits give a
possible combination of four functional types from the point of view of
regeneration after fire, and different relative proportions of these plant types may
determine the post-fire regeneration and erosion risk. Field observations in Spain
show better regeneration in limestone bedrock type than in marls, and in north-
facing slopes than in south-facing ones. Models of vegetation dynamics can be
built from the knowledge of plant traits and may help us in predicting post-fire
vegetation and long-term vegetation changes under recurrent fires.

The role of fire in European Mediterranean Ecosystems 2
2.1. Introduction
There are several features that make the landscapes of the European
Mediterranean Basin different from those of the rest of Europe, and these
differences are mainly related to the climate, the long and intense human impact,
and the role of fire. The latter is, in turn, influenced by the other two.
Mediterranean ecosystems of Europe have been subjected to a long-term history
of human use (Wainwright 1994, Grove 1996, Margaris et al. 1996), and this has
provoked older and very intense disturbance regime when compared to the other
Mediterranean-climate regions in the world (Fox and Fox 1986). However, within
the Mediterranean basin, differences in land-use patterns have increased during
this century between Euro-Mediterranean and Afro-Asiatic-Mediterranean
countries (Blondel and Aronson 1995). In the southern areas of the western
Mediterranean (Maghreb), growing populations are reducing forests and
shrublands by overgrazing and extending arable lands, whereas in the northern
countries abandoned land is increasing at the expense of marginal agriculture
(PuigdefÆbregas and Mendizabal 1998). These differential trends make the
European Mediterranean Basin more fire prone than the southern area, as shown
in the fire statistics of the last decades (VØlez 1997, Moreno et al. 1998).
2.2. Fire history
2.2.1. Statistics
Natural fires are common in many parts of the world and are an integral part of
many terrestrial ecosystems. Fire has been used by man as a management tool
since early times. It has been suggested that Palaeolithic people already burnt
deliberately to facilitate hunting and food gathering (Stewart 1956). The first
evidence of human-induced changes by fire in the Mediterranean landscape is
during the Neolithic (Naveh 1975). Since then, the Mediterranean basin has seen
the evolution of many cultures, some with high population densities, and most
making use of fire and farming. However, from the 60s until today the general
trend in number of fires and surface burnt in the European Mediterranean areas
(mainly Iberian, Italic and Greek Peninsulas and surrounding islands) has
increased exponentiallyFire statistics compiled for Spain from the 60s (Mart nez-
Ruiz 1994, Moreno et al. 1998, Piæol et al. 1998) show a clear increase in number
of fires and surface burnt especially since the mid-70s (Fig. 2.1 and 2.2). From
1960 to 1973 the mean annual burnt area was about 50 kha and the annual number
of fires was less than 2000. However, since 1974, the mean annual area burnt is
about 215 kha, caused by a mean of 8550 annual fires, and in some of these years
the area burnt was more than 400 kha, i.e. nearly 2% of the total non-arable land
of Spain (1978, 1985, 1989 and 1994; Fig. 2.1). This increase has occurred in spite
of the increased fire suppression efforts of the recent years. A similar trend has
been found in other European Mediterranean areas (e.g. Kailidis 1992, Viegas