Valdivian temperate forests

Category: Forest Biomes.

Geographic Location: South America.

Summary: A virtual continental island between the Pacific Ocean and the Andes Mountains, these forests boast high species endemism but face growing threats from human activities and climate change.

The Valdivian Temperate Forests biome is one of the few temperate rainforest areas in South America. Sandwiched between the Pacific Ocean and the Andes Mountains in the southern reaches of Chile and a small area of Argentina, the distribution area constitutes a virtual continental island. Species richness is relatively low, but the rate of species found only here, or endemism, is exceptionally high—about 45 percent for all vertebrates, and up to 90 percent of seed plants.

Phylogenetic uniqueness is also high; for example, there are 32 genera of trees, of which four-fifths are monotypic, meaning the genus comprises just a single species. These factors all indicate long and ancient isolation.

Geography and Climate

Wet temperate forests dominate the narrow strip between the western slopes of the Andes and the Pacific Ocean, from just north of the Chilean capital Santiago to the southern tip of the Taitao Peninsula. The forests are found in two north-to-south running mountain ranges as well as the intermediate valley. The peaks of the Andes are higher toward the north, about 23,000 feet (7,000 meters) higher than the southern range, which peaks at 13,123 feet (4,000 meters). Treelines are the same, at roughly 7,874 feet (2,400 meters). Forests are replaced by montane grasslands and shrublands above the treeline in the north, and by temperate grasslands, shrublands, and savannas further south.

The Andes were extensively glaciated during the Pleistocene Era, although volcanic rock and deposits have since covered most of the glaciated surfaces. The coastal range, Cordillera de la Costa, is a mountain belt rising to 4,265 feet (1,300 meters). It lies parallel to the coast and the Andes, which remained largely unglaciated. It submerges off the shore south of 42 degrees south, but then forms the large Chiloé Island and the Chonos Archipelago. Between the two mountain ranges lies a low structural depression valley, which submerges into the ocean at the same point.

The depression is filled with volcanic ash, erosion and glacial deposits; this fertile valley in the northern reaches of the biome is Chile’s agricultural heartland. Its climate results in a mediterranean vegetation type which separates the temperate forests of the eastern and western mountain ranges. These two temperate systems join further south.

The northward flowing Pacific Ocean currents combine with the dominant moist, westerly onshore winds to produce a maritime cool climate overall. This produces higher humidity and precipitation in the coastal range than in the Andes, and on the western slopes than on eastern slopes. In the south, rain falls year-round, with annual precipitation exceeding 236 inches (6,000 millimeters). A shift toward a winter rainfall regime and annual precipitation of about 39 inches (1,000 millimeters) occurs in the north. Coastal upwelling causes year-round coastal fog. Average annual temperatures vary between maxima of 55–70 degrees F (13 to 21 degrees C) and minima of 39–45 degrees F (4 to 7 degrees C) in the north and south, respectively.

Biodiversity

Southern beeches of the genus Nothofagus are widespread; this genus is found around the southern Pacific Rim, indicating a common evolutionary history reaching back to Gondwana.

Precipitation and, to a lesser extent, disturbances and latitudinal and altitudinal temperature differences, determine the distribution of vegetation types. The shade-intolerant Nothofagus species, which do not regenerate in undisturbed old-growth forests, are characteristic. They are widespread in the Andes due to periodic disturbances including volcanic eruptions and avalanches. Disturbances are less important in the coastal mountains where shade-tolerant trees are abundant.

Five main types of forest ecosystems can be distinguished. Northern deciduous forests with dominant Nothofagus species, including rauli and roble, mark the transition to mediterranean forests. Valdivian laurel-leaved forests are typical for the Nothofagus gap, and are dominated by broadleaf evergreen tree species, including tepa, ulmo, tiaca, tineo trees, and an understory of myrtle trees and arrayán.

Northern Patagonian forests are dominated by evergreen species such as coihue (N. dombeyi). Patagonian Andean forests feature the monkey-puzzle tree, a living fossil and Chile’s national tree, and the valuable and threatened alerce. High Andean scrublands with Nothofagus dominate nearer the treeline. Magellan’s beech (N. betuloides) and bogs of Sphagnum mosses typify southern evergreen forests.

Endemic bamboo species are characteristic understory species and can form dense, pure thickets. Edible, large-leaved perennial nalca and ferns are widespread. The copihue, Chile’s national flower, is a representative pioneer in disturbed areas.

Mammal endemism is relatively low here, but there are five endemic genera, including the monito del monte, an arboreal marsupial. Endemism levels for both reptiles and amphibians are high, with many species restricted to very small areas. They constitute important species targeted by the Alliance of Zero Extinction scheme.

About 30 percent of the bird species here are estimated to be endemic. There is just a single species of hummingbird, (Sephanoides sephaniodes), but it is vital to the one-fifth of woody plant genera that depend on its visits to spread pollen between their typically red, tube-like flowers.

Threats and Conservation

Before the arrival of the Spanish colonizers centuries ago, the indigenous Mapuche people cultivated only a few open areas, leaving the forest cover intact. After the colonizers’ arrival, heavy logging, burning, land clearance and habitat degradation began. Invasive species and, since the 1970s, ever-increasing pine and eucalyptus plantation forests, have caused significant damage. Today, few primary forests remain, especially in the coastal range.

Chile’s economy is one of the fastest-growing in Latin America, exercising strong human pressures on remaining forest fragments through tourism, construction of highways, and forest clearing for power lines, connecting the economic heartland with the hydroelectricity-producing areas in the south. There is a large network of protected areas, but—especially in the north—they are concentrated at middle elevations in the Andes, leaving the coastal range under further pressure. The area with the highest biodiversity (36–41 degrees south) has the lowest percentage of protected areas.

The analysis of historic plant distributions shows substantial variations, and indicates a high sensitivity of temperature regimes. Climatic change and geographic isolation seem to have resulted in a net loss of species over time, which lends credence to current observations that this ecoregion is highly susceptible to global warming.

The Valdivian Temperate Forests ecoregion is part of a Conservation International hot spot. Together with the Juan Fernández Islands it constitutes a World Wildlife Fund Global 200 ecoregion, and also belongs to the Top 100 Ecoregions, a list of those biomes with the highest richness-adjusted endemism of vertebrates in the world.

However, intensive logging and land conversion for forest plantations, agriculture, and economic development severely threaten this biome—in particular by fragmenting habitats and opening the door to invasions by exotic plants and vertebrates. To combat the problems affecting the forest, groups such as the Nature Conservancy have been implementing conservation programs in the region. Among them have been efforts to reforest 8,400 acres with native trees and programs to fun sustainable beekeeping and tree harvesting.

Bibliography

“Chile's Valdivian Coastal Reserve: Saving Ancient Forests.” Nature Conservancy, 2022, www.nature.org/en-us/about-us/where-we-work/latin-america/chile/stories-in-chile/valdivian-coastal-reserve/. Accessed 19 Aug. 2022.

Funk, S. M. and J. E. Fa. “Ecoregion Prioritization Suggests an Armoury Not a Silver Bullet for Conservation Planning.” PLoS ONE 5 (2010).

Smith-Ramirez, C. and J. J. Armesto. “Plant Phenology in a South American Temperate Rainforest, Chiloe, Chile.” Journal of Ecology 82 (1994).

Veblen, T. T., C. Donoso, F. M. Schlegel, and R. Escobar. “Forest Dynamics in South-Central Chile.” Journal of Biogeography 8 (1981).