324
including all species; of which only 31% are commercially valuable species
(Handroanthus lapacho, Juglans australis, Cedrela saltensis, Patagonula americana, and Parapiptadenia excelsa). The Bosque Montano is mainly represented by
Podocarpus parlatorei and Alnus jorullensis and to a lesser extent Juglans australis.
It has a large area without forest exploitation due to the difficult accessibility and
low value of the woods. However, these forests are subjected to grazing pressure
throughout the year (Del Castillo et al. 2005).
Physical and biological changes along the altitudinal gradient determine uses
and conservation strategies (Malizia et al. 2012). In addition, it has been proposed
that the climatic history of the region with glacial refuges in the Northern Yungas
during the Pleistocene (Pennington et al. 2000) would have contributed to configurate the current pattern of biological diversity revealed from the geographic distribution of endemic species (Brown et al. 2001, 2006).
The main environmental service of the Yungas is the water provision for irrigation and human consumption (Balvanera 2012), having an influence over approximately 400,000 ha of crops and more than 2 million people. Regarding good’s
provision, native forests continue to be the main source of quality wood in the
NWA. The Yungas is the traditional supplier of the domestic hardwood market and
even has a surplus that is traded abroad, but unplanned logging is a threat to a sustained supply. The main problem is the informal trade of native woods: according to
estimations, 40% of the declared volumes comprises illegal timber. The problem is
due to the reduction of natural stocks because of selective extraction and the significant increase in illegal logging (Fornes et al. 2016). The overexploitation of the
Yungas along the second half of the last century has been particularly alarming and
has caused habitat forest disturbance (Grau and Brown 2000; Brown and Pacheco
2006). Since 1960, mechanization led to overexploitation of the Yungas. Thus, continuous selective logging for 50 years in a regional context of unsustainable management and lack of control and transparency of the local markets led to a deep
ecological impact on accessible forests (Grau and Brown 2000).
The Argentinean Yungas’ transformation into crops and urbanization achieved to
30% of its original surface in the year 2010, while in 1970 the grade of transformation was 18% (Malizia et al. 2012). The highest levels of landscape transformation
in South America between 2001 and 2010 were recorded at the transitional area
between the Chaco forest and the basal altitude of the Yungas (Volante et al. 2012;
Aide and Grau 2004). It is estimated that the remaining area of the Yungas is
3,726,835 ha (Malizia et al. 2012). The Selva Pedemontana is the altitudinal floor of
the Yungas most affected by transformations, mainly in flat lands below 5% slope,
where it is estimated that more than 80% of the original area has been already transformed (Gutiérrez Angonese and Grau 2014).
The forestry exploitation of the Yungas Rainforest, although with very low
impact intensity, began at the time of the colony, mainly in the Province of Tucumán,
where “the abundance of excellent wood made it easier for its inhabitants to build
good carts” (Levene 1940). The carriage industry became a relevant economic
activity at that time in NWA. The arrival of the railroad to Tucumán in 1876
promoted the development of the timber exploitation at an important commercial
L. F. Fornes
including all species; of which only 31% are commercially valuable species
(Handroanthus lapacho, Juglans australis, Cedrela saltensis, Patagonula americana, and Parapiptadenia excelsa). The Bosque Montano is mainly represented by
Podocarpus parlatorei and Alnus jorullensis and to a lesser extent Juglans australis.
It has a large area without forest exploitation due to the difficult accessibility and
low value of the woods. However, these forests are subjected to grazing pressure
throughout the year (Del Castillo et al. 2005).
Physical and biological changes along the altitudinal gradient determine uses
and conservation strategies (Malizia et al. 2012). In addition, it has been proposed
that the climatic history of the region with glacial refuges in the Northern Yungas
during the Pleistocene (Pennington et al. 2000) would have contributed to configurate the current pattern of biological diversity revealed from the geographic distribution of endemic species (Brown et al. 2001, 2006).
The main environmental service of the Yungas is the water provision for irrigation and human consumption (Balvanera 2012), having an influence over approximately 400,000 ha of crops and more than 2 million people. Regarding good’s
provision, native forests continue to be the main source of quality wood in the
NWA. The Yungas is the traditional supplier of the domestic hardwood market and
even has a surplus that is traded abroad, but unplanned logging is a threat to a sustained supply. The main problem is the informal trade of native woods: according to
estimations, 40% of the declared volumes comprises illegal timber. The problem is
due to the reduction of natural stocks because of selective extraction and the significant increase in illegal logging (Fornes et al. 2016). The overexploitation of the
Yungas along the second half of the last century has been particularly alarming and
has caused habitat forest disturbance (Grau and Brown 2000; Brown and Pacheco
2006). Since 1960, mechanization led to overexploitation of the Yungas. Thus, continuous selective logging for 50 years in a regional context of unsustainable management and lack of control and transparency of the local markets led to a deep
ecological impact on accessible forests (Grau and Brown 2000).
The Argentinean Yungas’ transformation into crops and urbanization achieved to
30% of its original surface in the year 2010, while in 1970 the grade of transformation was 18% (Malizia et al. 2012). The highest levels of landscape transformation
in South America between 2001 and 2010 were recorded at the transitional area
between the Chaco forest and the basal altitude of the Yungas (Volante et al. 2012;
Aide and Grau 2004). It is estimated that the remaining area of the Yungas is
3,726,835 ha (Malizia et al. 2012). The Selva Pedemontana is the altitudinal floor of
the Yungas most affected by transformations, mainly in flat lands below 5% slope,
where it is estimated that more than 80% of the original area has been already transformed (Gutiérrez Angonese and Grau 2014).
The forestry exploitation of the Yungas Rainforest, although with very low
impact intensity, began at the time of the colony, mainly in the Province of Tucumán,
where “the abundance of excellent wood made it easier for its inhabitants to build
good carts” (Levene 1940). The carriage industry became a relevant economic
activity at that time in NWA. The arrival of the railroad to Tucumán in 1876
promoted the development of the timber exploitation at an important commercial
L. F. Fornes