The Mediterranean Biome: Five Global Hotspots of Fire and Endemism

The Mediterranean biome — characterised by mild, wet winters and hot, dry summers — occurs in only five widely separated regions: the Mediterranean Basin, California, Central Chile, the Cape Floristic Region of South Africa, and Southwest Australia. Despite covering less than 5% of Earth's land, these five regions contain approximately 20% of all plant species — a botanical diversity exceeded only by tropical rainforests. The Cape Floristic Region alone contains over 9,000 plant species in an area smaller than Portugal — 70% of them found nowhere else on Earth. The Mediterranean climate is also the only climate type reliably associated with fire-adapted vegetation: summer drought combined with combustible shrubs makes fire a fundamental ecological process, and the plants of these regions show clear evolutionary adaptations to periodic burning.

Convergent Evolution — Similar Solutions

The five Mediterranean biome regions are biologically independent — separated by oceans and continents, with few species shared between them. Yet they have converged on remarkably similar plant forms in response to the same climate. Sclerophyllous leaves — thick, hard, waxy-coated to reduce water loss during summer drought — appear independently in the oaks and maquis of the Mediterranean Basin, the chaparral shrubs of California, the matorral of Chile, the fynbos of South Africa, and the kwongan of Australia. Deep root systems to access groundwater during summer drought appear in all five regions. Smoke-triggered germination — a mechanism by which seeds germinate only after exposure to the specific chemicals produced by burning vegetation — has evolved independently in hundreds of species across all five regions, representing one of the most striking examples of convergent molecular evolution in plants.

Climate Change Threats

All five Mediterranean biome regions are among the most climate-vulnerable on Earth. Climate projections consistently show Mediterranean climates becoming hotter and drier, extending the summer drought period, increasing the frequency and intensity of wildfires, and expanding the thermal envelope beyond the tolerance of many endemic species. The Mediterranean Basin — bordered by the Middle East, North Africa, and southern Europe — is projected to experience some of the largest temperature and precipitation changes of any populated region under continued warming. Fire seasons are already lengthening across California, Australia, and the Mediterranean Basin. The endemic species of these biodiverse hotspots — many with small geographic ranges and narrow climate tolerances — face extinction risks that are among the highest of any terrestrial biome.

Mediterranean Agriculture — 10,000 Years of Coevolution

The Mediterranean Basin is the cradle of Western agriculture — the region where wheat, barley, lentils, chickpeas, olives, grapes, and many other foundational crops were first domesticated, beginning approximately 10,000 years ago in the Fertile Crescent and spreading across the Mediterranean over the following millennia. This long agricultural history has profoundly shaped Mediterranean biodiversity: traditional extensive farming systems, particularly the dehesa and montado tree-pastures of Iberia (scattered cork and holm oaks over grazed grassland), the olive groves of the eastern Mediterranean, and the agro-silvo-pastoral systems of North Africa, have co-evolved with native flora and fauna over millennia to create some of the most biodiverse agricultural landscapes on Earth. Spanish dehesa supports breeding populations of imperial eagles, black vultures, and lynx; traditional Cypriot olive groves shelter densities of migrant birds that exceed those in natural scrubland; and the ancient field systems of Crete maintain plant communities of extraordinary botanical richness.

Mediterranean Megafires — The New Normal

The Mediterranean biome has always been a fire-prone landscape, but the combination of climate change (hotter summers, extended drought, more extreme fire weather) and land use change (rural depopulation leading to the accumulation of unmanaged fuel loads in abandoned agricultural land) is producing a new fire regime — one of larger, more intense, and less predictable fires that exceed the capacity of existing fire suppression infrastructure and that may be outside the adaptive range of even fire-adapted native vegetation. The 2021 Greek wildfires burned over 100,000 hectares in a single week; the 2020 California fire season burned over 1.7 million hectares; and the 2019-2020 Australian Black Summer fires burned approximately 18 million hectares of bush — including large areas of previously fire-rare wet forests and rainforest. These mega-fire events are not simply extreme versions of historical fire regimes but qualitatively different phenomena, burning at intensities and extents that kill fire-adapted plants and prevent the natural regeneration processes that historical fire regimes supported.