Yungas of northwestern Argentina: biodiversity and water reserve

Characteristics and distribution of the Yungas

According to the National Council for Scientific Research (CONICET) of Argentina, “the Yungas jungle is an ecoregion that ranges from the department of Santa Cruz in Bolivia to the province of Catamarca in northern Argentina, which is characterized by being a cloudy forest, product of the orography of the Andes ”(Yungas, the green treasure). Indeed, the Yungas are formed thanks to the orographic summer rains, when the humid masses (coming from the Atlantic) rise by contact with the sub-Andean and Pampean mountain ranges, and with the eastern mountain range, on their slopes facing east.

The Biodiversity Information System (SIB) of the Administration of National Parks of Argentina, states that, in the Yungas, “Altitudes vary between 400 and 3,000 m. Annual precipitation is of the order of 900 to 1,000 mm, reaching 1,300 mm in some places. The rains are preferably summer or are concentrated over 5 to 6 months. During the colder months, the condensation and water uptake of the mist that characterizes these cloudy forests, partially compensate for the absence of rain. The mountainous structure and the marked rainfall on the eastern slopes generate a fairly organized river network ”.

These mountain forests, one of the most biodiverse ecoregions in Argentina (along with the missionary or Paraná jungle), stand out for presenting several floors or strata of vegetation, configured according to their altitude above sea level.

The altitudinal variation gives rise to different strata of vegetation

The report on the Yungas Biosphere Reserve (Fundación ProYungas, 2010) describes the altitudinal levels of vegetation in these forests:

• Neblina Pasture: 2400–3500 masl; hilltops, pastures with isolated queñoa trees; high rainfall and frequent fogs. Main disturbances: fire and overgrazing
• Montane Forest : 1500–3000 masl; it borders the “fog grasslands”; heavy rainfall and very frequent fogs; forests in different stages of recovery due to the effect of fire. Main disturbances: fire and overgrazing.
• Montana Forest: 700–1500 masl; slopes of the mountains; Altitudinal strip of maximum rainfall. Main disturbances: landslides on slopes.

• Pedemontana Forest: 400–700 masl; in the foothills and low-lying mountains. Transformed to a large extent in areas of intensive agriculture, mainly sugar cane and soybeans. Main disturbances: forest fires, erosion of the banks of streams and rivers caused by their wandering meandering courses, typical of the foothills.

Natural areas that protect the Yungas ecoregion

According to the aforementioned SIB, the Yungas ecoregion has, in Argentina, an area of 4,780,677 ha, with 268,164 ha in national protected areas: the Baritú, Calilegua, El Rey, Aconquija and Los Cardones National Parks, and the National Reserves The Nogalar de los Toldos and Pizarro.

The final report made in 2011 by Lic. Amélie Le Ster, for the UNESCO Young Scientists Scholarship, states that “ the Yungas Biosphere Reserve was declared in 2002 by the UNESCO MAB (Man and Biosphere) Program , in order to preserve a portion of the mountain forests called Yungas in the Argentine Northwest, also called the Tucuman-Bolivian jungle or the Tucuman-Oranian jungle ”.

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Said research adds that “the Yungas Biosphere Reserve is characterized by being trans-provincial, including the territory of the provinces of Jujuy (30%) and Salta (70%) with an area of approximately 1,350,000 ha, among the 300 m and 5,000 m of altitude, being one of the largest in Argentina ”.

Habitat fragmentation and threats

"In addition to the infrastructure process, irrational logging of the forest and the negative impact of livestock on natural regeneration, external factors have had an impact to generate and maintain total anarchy in forest exploitation, aptly named because it was never an exploitation (Selva de Yungas del Northwest Argentina –Jujuy, Salta, Tucumán-, Environmental and Productive Recovery, National Institute of Agricultural Technology).

“In this region an intense process of fragmentation and degradation of forests is observed due to the replacement of these by agriculture and the selective use of valuable forest species. In the south of the province of Salta, the traditional use of the land produces an appearance of mosaic or patches of different successional states ”(Analysis of Fragmentation and Landscape Structure in Native Forests of Northern Argentina, Advances in Renewable Energies and Middle Environment Vol. 16, 2012).

The Yungas are a refuge for endangered species such as the tapir and the jaguar

This forest not only treasures trees of great value, and provides environmental benefits for the population; It is also home to emblematic animals such as the tapir (a vulnerable species, with a decreasing population trend according to the IUCN), and the jaguar (declared a National Natural Monument in Argentina by Law 25,463 of 2001). Consequently, the conservation of the remaining fragments of the Yungas, which once constituted a forest continuum, is essential for the future of the enormous biodiversity that this ecoregion harbors.