History and Distribution of the Temperate Forests

• The Coastal Range Coalition
• Biodiversity
• Cultural diversity
• History of the temperate forest
• Threats to the rainforest
• Tourism

   The temperate forests of South America are concentrated in a narrow longitudinal band no more than 200 km in width, situated between the long Chilean coast of the Pacific Ocean and the eastern foothills of the Andes, between 35º degrees latitude in Central Chile and 56º degrees in Tierra del Fuego (Smith 2000).

   The origin of these forest formations dates back millions of years.  A global tendency of cooling in the Tertiary period, coinciding with tectonic processes caused the emergence of the Andean mountains in the southeastern part of South America.  As a result of this, the southern forests became gradually isolated from other forests of the continent (Smith, 2000)

    Arid climate barriers appeared in the north of Chile and in Patagonia; caused  by the Andean mountain range which reached elevations that blocked the trajectories of humid western winds, 30º to the south  and the frontal monsoons of the east, and to the north of 30º.  During the last 3 to 5 million years, the arid conditions and the altitude barrier of the mountain range also interrupted the flow, or biologic transition, between the tropical latitudes of the eastern Andes and to the western side of the continent.  This separation reflects the elevated number of taxa in the temperate forest which has unequalled levels of distribution of genus, making it the most extensive of the tropical latitude forests.  Some important genus found in the southern forests have related species in the high, cold areas of northern Brazil, eastern and northeastern Bolivia, and the northern Andes almost all the way to Central America.
The arid conditions intensified during the glaciation, further restricting the area of temperate forests.  They were pushed up to Ecuador by the expansion of glaciers in the south, augmenting their isolation (Smith, 2000).

    At this time there occurred a series of alternating heating and cooling, the mountain glaciers  advanced and retreated numerous times during the Pleistocene Era (1.8 million years ago), causing successive  contractions and expansions of the area of the temperate forests.  The immigration of species from the tropical latitudes already was not possible because of the conditions of the northern  aridity and the mountain range of the west. So the immigrations of species during the hot periods between glaciation was not able to compensate for the extinction of species during the periods of cooling.  The growth of the arid north and the isolation possibly produced the great number of present monotypic genus of plantlife  in this temperate forest. The lack of immigration caused a loss of species, particularly the taxas  linked to  tropical ancestors. Estimates figures  indicate that around 60% of the preexisting plants with tropical affinities have become extinct because of the environmental changes since the late Tertiary period (5 million years ago).  The diversity of birds associated with forests of the southern latitudes also seem to have reduced considerably during the Pleistocene Era (Smith, 2000).

    As the glaciers covered a large part of southern South America, the biodiversity of the forests survived in small glacial refuges between icefields and on the  outskirts of this   territory.  For the majority of the forest species,  descended from tropical ancestors, the refugees were situated in the coastal area, near the northern limit of the actual forests, where the precipitation was presumably more and the temperatures were moderate because of the maritime influence.  Some of the areas of the coast between 38º and  40º degrees maintained themselves without ice and the glacial processes that continued to affect the vegetation further south.  It was able to be estimated, through the reconstruction of the extensive fields of ice, that the area covered by the temperate forests had been greatly reduced by the Last Glacial Maximum, 21,000 years in the past, to around 1/3 of their actual range.). Small patches of some conifers (Alerce) and species of Nothofagus were able to persist in the vicinity of the glaciers by their capacity to grow  in poor or flooded soils.  The location of the refugee forests is confirmed by the  peak  in taxonomic richness of trees observed between 35º and 40º south, and through the results of palynologic studies in the region the Lake District and the island of Chiloé, which documented a rapid expansion of tree species from the coastal area, beginning  around 12,000 years ago and continuing today (Smith 2000).

    The study  of the colonization by the forests after the last glaciation suggests that the current forests are able to expand their distributional ranges as an answer to the warming climate.  The colonization by  the taxa of the Valdivian forest, in the Lake district, and of the island of Chiloé was rapid and began 12,000 years ago, immediately following the increase of temperature. Nevertheless, not all the species distributed themselves at the same rate. Some studies have revealed trees in the Andes that date back just 3000-5000 years.  The colonization of Nothofagus trees in the southern region of Patagonia progressively occurred during the last 10,000 years (Smith, 2000).

    The climatic and topographic complexity of our country, on account of its length that travels a total of 38º latitude, has caused its biogeographic diversity and the variety of endemic biota that exist today (Smith, 2000).

    A staggering amount of species are endemic to this region. The temperate forest contains 51.2% of native plantlife, 77% of amphibians, 80% of (bryozoos) and an astounding 92% of hemiterphenes and heteropters.

The history of  human forest use can be classified in four stages. (Armesto et al,  1994)

The Indigenous Period:
From around 10,000 years ago until approximately the sixteenth century, indigenous tribes mostly occupied the coastal areas and the central valley. Their survival depended on agriculture and fishing. The ability for controlled burning and clearing the forests was limited  due to  the lack of  metal instruments used to cut trees. According to chronicles of the seventeenth and eighteenth centuries, in the the southern central area between 33 degrees and 45 degrees longitude, Chile resembled a dense, wooded landscape.

The Colonization:
The Spanish colonization initiated an intense extraction of wood for construction of towns and ships, also the forests were burned back in order to open land for fields and domestic animal pastures.  The large scale extraction of wood began to form the opinion of the colonizers that forest products were inexhaustable.  The colonization phase is able to be divided into two parts: colonial, which brought the rapid destruction to the forests between Maule and Concepción and republic,, principally after 1850, during which the european colonization reached the southern portion of Chile, in regions IX and X, where many ancestors still remain.

The Seclective Exploitation:
From the mid-nineteenth century until the mid-twentieth century, the use of the native forest was based in a selective destruction, which invaded a large part of the forests in the central valley and accessible coast,  and, subsequently, deteriorated older examples of the intrinsic endemic species. This phase was characterized furthermore by the extensive burning of forests in order to gather species of trees whose wood had high value, some of the types being: the old growth alerce, the araucaria and the cypress of Guaitecas—all which resist  fire and may be taken once all the surrounding plantlife has been burnt away.

The Industrial Era:
Since 1950 there has arisen a business mentality that can be characterized by the major levels of destruction and exploitation of the native forest that is unmatched by the past.  The establishment of sawmills  and the industries’practice of replanting foreign fast growing monotypes, especially pine plantations, have added rapid growth to the destruction of Chile´s native forests.

The consequences of using the forest this way will result to degradation and fragmentation.  The public estimates indicate that, before the colonization phase, around 30 million hectares existed.  Today there are only 7.5 million hectares remaining (Armesto et al, 1994).  On another point, the catastrophe of Chile´s forest groundcover wass realized in 1997 by CONAF, who found that the surface area of the forest is 15,647,894 hectares (20.8% of the national surface area)  Of this, 13,443,316 hectares correspond to the native forest (including renovations), and compose 17.8% of Chile’s surface area. (back)