Mediterranean forests, woodlands, and scrub

Mediterranean wood pasture in Salamanca, Spain: single mature evergreen oak trees of uniform age without natural undergrowth due to pastoral land use. The trees of uniform age, pictured here, will age and die roughly at the same time, without human intervention or costly reforestation. The landscape will degrade to a maquis shrubland as succession.

Mediterranean forests, woodlands, and scrub biome, as defined by the World Wildlife Fund, is characterized by dry summers and rainy winters. Summers are typically hot in low-lying inland locations but can be cool near colder seas. Winters are typically mild to cool in low-lying locations but can be cold in inland and higher locations.

The Mediterranean forests, woodlands, and scrub biome occurs in the world's five Mediterranean climate zones, on the west coast of continents in the mid-latitudes:^[1]

A Mediterranean forest, the Upper Galilee

• the Mediterranean Basin
• the Chilean Matorral
• the California chaparral and woodlands ecoregion of California and the Baja California Peninsula
• the Western Cape of South Africa
• the Southwest Australia corner area

Diversity

Eucalyptus forest in a state of regeneration after a fire

These regions are home to a tremendous diversity of habitats and species. Vegetation types range from forests to woodlands, savannas, shrublands, and grasslands; "mosaic habitat" landscapes are common, where differing vegetation types are interleaved with one another in complex patterns created by variations in soil, topography, exposure to wind and sun, and fire history. Much of the woody vegetation in Mediterranean-climate regions is sclerophyll, which means 'hard-leaved' in Greek. Sclerophyll vegetation generally has small, dark leaves covered with a waxy outer layer to retain moisture in the dry summer months.

All these ecoregions are highly distinctive, collectively harboring 10% of the Earth's plant species.^[2] Phytogeographers consider the fynbos (South Africa) as a separate floral kingdom because 68% of the 8,600 vascular plant species crowded into its 90,000 square kilometres (35,000 sq mi) are endemic and highly distinctive at several taxonomic levels.^[1][3] This is equivalent to about 40% of the plant species of the United States and Canada combined, found within an area the size of the state of Maine. The fynbos and Southwest Australia shrublands have flora that are significantly more diverse than the other ecoregions, although any Mediterranean shrubland is still rich in species and endemics relative to other non-forest ecoregions.^[1][3]

Biome plant groups

A mediterranean cork oak savanna, in Alentejo region, Portugal.

Major plant communities in this biome include:

• Forest: Mediterranean forests are generally composed of broadleaf trees, such as the oak and mixed sclerophyll forests of California and the Mediterranean region, the Eucalyptus forests of Southwest Australia, and the Nothofagus forests of central Chile. Forests are often found in riparian areas, where they receive more summer water. Coniferous forests also occur, especially around the Mediterranean. Pine and deciduous oak forest are widespread across California
• Woodland: Oak woodlands are characteristic of the Mediterranean Basin and in California. Pine woodlands are also present in the Mediterranean Basin. California additionally has walnut woodlands.
• Savanna and grassland: The California Central Valley grasslands are the largest Mediterranean grassland eco-region, although these grasslands have mostly been converted to agriculture. The remaining woodlands feature mainly oak, walnut and pine. The cork oak savanna in Portugal, known as montado, is a good example of a mediterranean savanna.
• Shrubland: Shrublands are dense thickets of evergreen sclerophyll shrubs and small trees. They are most common near the seacoast, and are often adapted to wind and salt air from the ocean. They are called chaparral (California and southern Portugal), matorral in Chile and southern Spain, garrigue or maquis in France, macchia or gariga in Italy, phrygana in Greece, tomillares in Spain, fynbos and strandveld in South Africa, kwongan in Southwest Australia and batha in Israel. Northern coastal scrub and coastal sage scrub, also known as soft chaparral, occur near the California coast. In some places shrublands are of the mature vegetation type, and in other places are the result of degradation of former forest or woodland by logging or overgrazing, or disturbance by major fires.

Fire as a medium of change

Scrubland in Aliso Canyon, Santa Susana Mountains, Southern California.

Fire, both natural and human-caused, has played a large role in shaping the ecology of Mediterranean ecoregions. The hot, dry summers make much of the region prone to fires, and lightning-caused fires occur with some frequency. Many of the plants are pyrophytes, or fire-loving, adapted or even depending on fire for reproduction, recycling of nutrients, and the removal of dead or senescent vegetation. In both the Australian and Californian Mediterranean-climate eco-regions, native peoples used fire extensively to clear brush and trees, making way for the grasses and herbaceous vegetation that supported game animals and useful plants. The plant communities in these areas adapted to the frequent human-caused fires, and pyrophyte species grew more common and more fire-loving, while plants that were poorly adapted to fire retreated. After European colonization of these regions, fires were suppressed, which has caused some unintended consequences in these ecoregions; fuel builds up, so that when fires do come they are much more devastating, and some species dependent on fire for their reproduction are now threatened. The European shrublands have also been shaped by anthropogenic fire, historically associated with transhumance herding of sheep and goats.

Degradation

Close up Ephesos ancient Greek amphitheatre with harbour street. Like the ancient city Miletus nearby, in antiquity the city possessed a natural harbour at the end of the street. Due to ancient and subsequent deforestation, overgrazing (mostly by goat herds), erosion and soil degradation the Turkey coastline is now 3-4 km away from the ancient site with sediments filling the plain and bare hill ridges without soils, woods—a maquis shrubland remaining.

Springtime in Chilean Matorral a few kilometers north of Santiago along the Pan-American Highway. In the background Aconcagua can be seen.

Mediterranean ecoregions are some of the most endangered and vulnerable on the planet. As such, many have suffered tremendous degradation and habitat loss through logging, overgrazing, conversion to agriculture, urbanization, fire suppression, and introduction of exotic and invasive species. The ecoregions around the Mediterranean basin and in California have been particularly affected by degradation due to human activity, suffering extensive loss of forests and soil erosion, and many native plants and animals have become extinct or endangered.

References

1. "Mediterranean Forests, Woodlands, and Scrub Ecoregions". WWF. Retrieved 2010-05-27. (included verbatim material: licensed under CC-BY-SA-3.0)
2. Cody, M.L. (1986). "Diversity, rarity, and conservation in Mediterranean-climate regions". In Soulé, M.E. Conservation biology: the science of scarcity and diversity. Sunderland, Massachusetts, USA.: Sinauer. pp. 122–152.
3. Cowling, R.M.; MacDonald, I.A.W.; Simmons, M.T. (1996). "The Cape Peninsula, South Africa: Physiographical, biological and historical background to an extraordinary hot-spot of biodiversity". Biodiversity and Conservation 5: 527–550. doi:10.1007/bf00137608.

External links

Media related to Mediterranean forests, woodlands, and scrub at Wikimedia Commons

• National Geographic Global 200 Ecoregions: Mediterranean Forest, Woodland and Scrub. Part of National Geographic's Wild World Terrestrial Ecoregions of the World mapping project.