Archive for July, 2012

Australian aboriginal fires preserve biodiversity

July 24th, 2012 1 comment

Traditionally, Australian aboriginal people set fires in their landscape to facilitate hunting. A recent study has compared the landscape and fire history from two regions, one where aboriginal people live in a traditional way and the other where fires are “natural” and caused by lightning [1]. The results show that aborigines generate many small fires that are climate-independent, while lightning generates few large climate-driven fires. Anthropogenic fires are smaller even when climatic conditions cause huge fire in the lightning region. The authors suggest that this climate-buffering effects of aboriginal fires has likely been important for many species that benefit both from fine-grained mosaics of alternating resources and from enhanced protection from large catastrophic fires and the predators that hunt within them. This may explain the coincident decline of many small- to medium-sized mammals in the arid regions of Australia with the cessation of aboriginal hunting and burning. That is, the extinction of the aboriginal life style shifted fire regimes from small fires to large climate-driven fires, in a similar manner to the extinction of rural life styles in the Mediterranean Europe [2], and this shift promoted the extinciton of Australian mammals.

Fire Dreaming, by Malcolm Maloney Jagamarra [from]


[1] Bird R.B., Codding B.F., Kauhanen P.G. & Bird D.W. (2012). Aboriginal hunting buffers climate-driven fire-size variability in Australia’s spinifex grasslands. PNAS, 109, 10287-10292. [pnas]

[2] Pausas J.G. & Fernández-Muñoz S. (2012). Fire regime changes in the Western Mediterranean Basin: from fuel-limited to drought-driven fire regime. Clim. Change, 110, 215-226.  [doi | springer | pdf]


Life 15 days after the large fires in Valencia

July 22nd, 2012 4 comments

Few days ago two simultaneously large fires occurred very near to Valencia city [1]: The first affecting Dos Aguas and surroundings (ca. 29000 ha burned), and the second in Andilla and surroundings (ca. 19000 ha burned). The fires burned under extreme fire whether conditions (strong drought, high temperature and strong dry wind [Foehn type wind]). 15 days after the fire, I visited area burned around Dos Aguas and took these pictures showing the postfire life activity; several species already started to resprout and pines were dispersing their seeds. In addition I saw several lizards, different birds and a fox, all in the middle of the recently burned area, quite far from the edge of the fire.

A. Chamaerops humilis (en: Mediterranean dwarf Palm, es: palmito, cat: margalló)

B. Resprout of Quercus coccifera (en: Kermes oak, es: coscoja, cat: garric, coscoll)

C. Resprout of Daphe gnidium (en: flax-leaved daphne, es: torvisco, cat: matapoll). The high intensity of the fire is clear from the thick remaining branch.

D. Post-fire seed dispersal of the serotinous cones of Pinus halepensis (en: Aleppo Pine , es: pino carrsco; cat: pi blanc).


[1] Incendios forestales en Valencia, Junio 2012,, 4/Julio/2012.


Bark harvesting and Cork oak vulnerability to fire

July 11th, 2012 No comments

Cork oak (Quercus suber) is a strong fire-resistant tree species thank to is very thick and insulating corky bark [1-4]. In fact it is the only European tree with the capacity to resprout from epicormic buds in the canopy after an intense crown-fire [1]. However, the bark of the cork oak is periodically harvested for cork production (mainly for bottle tops but also for other uses, [2]) and thus bark harvesting increases the vulnerability of the tree to fire. In a recent paper we quantified the response of cork oak (tree mortality, stem mortality, and crown recovery) after fire [5]. The results showed that fire vulnerability was higher for trees with thin bark (young or recently debarked individuals) and decreased with increasing bark thickness until cork was 3–4 cm thick. This bark thickness corresponds to the moment when exploited trees are debarked again, meaning that exploited trees are vulnerable to fire during a long period. Exploited trees were also more likely to be top-killed than never-debarked trees, even for the same bark thickness. Additionally, vulnerability to fire increased with burn severity and with tree diameter, and was higher in trees burned in early summer or located in drier south-facing aspects. All these aspects need to be considered when managing cork oak woodlands specially nowadays that fire activity is increased [6]. Increasing the length of the cork harvesting cycle would increase the time during which the trees have a thicker bark and are better protected against fire injury. Since cork is the main economical income from these forests, stopping bark exploitation might be unrealistic in most cases. However, in fire-prone areas where conservation and tourism are the main objectives, stopping bark explotation would likely be the most effective option to increase ecosystem resilience to fire. The valorisation of many other services provided by cork oak forests [7] could create economic incentives to decrease the bark-exploitation dependency of these systems in the future.

Foto: Cork oak  resprouting from epicormic buds (By F. Catry)


[1] Pausas, J.G. 1997. Resprouting of Quercus suber in NE Spain after fire. J. Veg. Sci. 8: 703-706. [doi | pdf]

[2] Aronson, J., J. S. Pereira, and J. G. Pausas (eds). 2009. Cork Oak Woodlands on the Edge: Ecology, Adaptive Management, and Restoration. Island Press, Washington, DC. [web of the book]

[3] Pausas J.G. 2009. Convergent evolution., 8/Nov/2009. [link]

[4] Pausas J.G. 2011. Bark thickness: a world record?, 3/Jan/201. [link]

[5] Catry F., Moreira F., Pausas J.G., Fernandes P.M., Rego F., Cardillo E. & Curt T. 2012. Cork Oak vulnerability to fire: the role of bark harvesting, tree characteristics and abiotic factors. PLoS ONE 7: e39810. [doi | pdf ]

[6] Pausas J.G. & Fernández-Muñoz S. 2012. Fire regime changes in the Western Mediterranean Basin: from fuel-limited to drought-driven fire regime. Climatic Change 110: 215-226. [doi | springer | pdf]

[7] Bugalho M.N., Caldeira M.C., Pereira J.S., Aronson J., & Pausas J.G. 2011. Mediterranean Cork oak savannas require human use to sustain biodiversity and ecosystem services. Frontiers in Ecology and the Environment 9: 278-286. [doi | pdf | blog]


Incendios forestales en Valencia, Junio 2012

July 4th, 2012 2 comments

¿Por qué se dan estos incendios?


  • El incremento de población urbana en el paisaje rural (chalets, urbanizaciones, actividades de fin de semana, etc…) aumenta la probabilidad de igniciones. Esto es debido a que muchas actividades humanas generan chispas o igniciones, tanto de manera accidental (vehículos, soldaduras, cocinas, cigarros, cableados, barbacoas, …) como intencionada (malhechores y pirómanos).
  • La disminución de la población rural (reducción del pastoreo, agricultura, recolección de leña, etc..) durante las últimas décadas conlleva un incremento de la cantidad de vegetación (combustible) en el paisaje. De manera que si se da un incendio, es más probable que sea de mayor tamaño e intensidad que anteriormente cuando el uso del monte era intenso.
  • La elevada sequía y las elevadas temperaturas hacen que la vegetación sea muy inflamable, y una fuente de ignición (chispa, etc.) pueda ser fuente de un incendio. El cambio climático aumenta la frecuencia de estas situaciones.
  • Los vientos de poniente en Valencia son muy secos, cálidos y relativamente fuertes. Si hay un incendio en estas condiciones, el fuego se propaga rápidamente y es prácticamente imposible detenerlo, hasta que no cambian las condiciones del viento.

Los días 28 al 30 de Junio de 2012 en Valencia se dieron todos estos factores. Las condiciones climáticas eran extremas, con temperaturas elevadas  (las máximas rondando 40 grados) y humedad muy baja (hacía al menos 2 meses que no llovía); en esas condiciones, las chispas prenden fácilmente. Además, hubo tres días seguidos de vientos secos y sin cambio de dirección (el poniente), que facilitó la rápida propagación del fuego. Los dos incendios que se dieron esos días afectaron aproximadamente a un total de 50000 ha. Los incendios se controlaron cuando el poniente calmó.


¿Qué podemos hacer para evitarlos?


No es fácil, y se requiere una política a largo plazo. La simple extinción no es suficiente, tal como hemos visto en muchas ocasiones, tanto en nuestro país como en otros (incluidos países tecnológicamente más avanzados y ricos). Aquí algunas ideas:

  • Disminuir la población urbana que vive en los paisajes inflamables, es decir, disminuir los chalets y urbanizaciones que tenemos en nuestros montes, reducir la interfaz urbano-forestal. En general las urbanizaciones en el medio natural son: 1) potenciales puntos de ignición; 2) puntos de desastre cuando se da un incendio (a menudo los incendios no son perjudiciales para la vegetación, que se regenera, pero causan problemas a los habitantes que viven en el monte); 3) son en sí mismos un problema para la biodiversidad, independientemente de los incendios (destrozan parte del paisaje y de la naturaleza, incrementan las especies invasoras, etc…).
  • Incentivar la vida rural y el uso sostenible de los montes. Introducir o facilitar a la presencia de herbívoros autóctonos (y sus depredadores).
  • Reducir el cambio climático, es decir, reducir las emisiones de gases efecto invernadero y cumplir con los protocolos de Kyoto sobre el cambio climático. Reducir el uso de energías contaminantes, etc.
  • Aceptar que siempre habrá incendios en nuestros montes mediterráneos, y aprender a vivir con ello. Diseñar con detalle las zonas donde se puede construir y donde no; limitar fuertemente el paso en los caminos rurales, especialmente en épocas propensas a incendios; regular las construcciones y sus alrededores considerando los incendios como parte del paisaje.

 Valencia, 30 Junio 2012.

Para más información:

Libro: Incendios forestales, Ed. Catarata-CSIC [enlace]

Incendios de ayer, de hoy y de mañana, Crónica Popular 6/7/2012  [enlace | pdf]

Pausas J.G. & Paula S. 2012. Fuel shapes the fire-climate relationship: evidence from Mediterranean ecosystems.  Global Ecol. Biogeogr. [doi pdf | post]

Pausas J.G. & Fernández-Muñoz S. 2012. Fire regime changes in the Western Mediterranean Basin: from fuel-limited to drought-driven fire regime. Climatic Change 110: 215-226. [doi | pdf post]

Pausas, J.G. 2004. Changes in fire and climate in the eastern Iberian Peninsula (Mediterranean basin). Climatic Change 63: 337-350. [doi pdf]

Pausas, J.G., Vallejo R. 2008. Bases ecológicas para convivir con los incendios forestales en la Región Mediterránea – decálogo Ecosistemas, 17(2): 128-129 (5/2008). [link | pdf]

Urban planning for fire management [link]

Book: Fire in mediterranean ecosystem [link]

The answer is blowing in the wind [link]