Grasslands and Open Savannas of the Dry Chaco

Abstract

The Dry Chaco is mostly known as a forested ecosystem. However it includes natural grasslands, savannas, scrublands, and wetlands. With one of the highest global deforestation rates in the last two decades and only 12% of the area protected, the concern about land-use change in this ecoregion has raised exponentially; but conservation initiatives developed in last years almost exclusively targeted forests whereas natural grasslands and savannas remain as neglected ecosystem within scientific and governmental agendas. While currently the distribution of natural grassland and savanna area encompasses over 20,000 km 2 , historical records and spatial models indicate that natural grassland and savannas were more widespread in pre-European era. Two main reasons drove this reduction in natural grasslands and savannas: woody encroachment by fire suppression and overgrazing, and conversion to agriculture and implanted pastures. In this article, through a combination of analyzes and bibliographic revisions, we describe biotic and abiotic components of natural grassland and savannas of the Dry Chaco. We also present the current distribution and conservation status of these ecosystems, and describe the process of change and the ecological consequences for biogeochemical cycles and biologic interactions. To provide basis for management, we estimate current grazing stocking rates on natural grasslands and savannas of Argentine Dry Chaco and we propose an alternative approach to sustainably intensify the use of these ecosystems and improve cattle rancher livelihoods. Despite the existent knowledge about natural grasslands and savannas in the region, we believe that is necessary to motivate the scientific community and national institutions to increase efforts to reconcile the restoration and conservation of these particular rangelands.

Land systems’ asymmetries across transnational ecoregions in South America

“…Fires were the most important variable characterizing land-use systems' asymmetries in biomes dominated by extensive ranching activities, such as dry forests, and tropical grasslands and savannas. Fire is used as a management tool associated to deforestation (for shifting or permanent cultivation), to promote grassland regrowth and palatability, to control shrubland encroachment in pastureland, and to prevent big fires by reducing fuel accumulation (Bowman et al 2011;Fernández et al 2020). Examples of regions where fire's density is reflecting land system asymmetries are the Dry Chaco forest between Bolivia and Paraguay or the Yungas between Bolivia and Argentina, where Bolivia has lower fire density in both cases (Table 2).…”

“…This land-use intensification brought associated important losses of natural vegetation in lowland plains (Aide et al 2013;Armenteras et al 2017;Hansen et al 2013). Yet, intense land uses co-exist with vast tracks of (grass) land managed in extensive ways using traditional fire techniques (Bowman et al 2011;Fernández et al 2020), large areas of forest recovery, mostly in mountain sectors (Aide et al 2019(Aide et al , 2013Nanni et al 2019) and the protection of land which differs importantly among countries and ecoregions (Baldi et al 2018).…”

Las arañas saltadoras (Araneae: Salticidae) como indicadoras del estado de conservación de los hábitats en el Chaco Oriental

“…Grassland cover has been reduced due to shrub encroachment caused by fire suppression and selective grazing that favor woody species (Grau et al 2015). Also, grasslands were reduced by conversion to agriculture and implanted pastures (Fernández et al 2020). Thus, this province requires conservation and restoration efforts to prevent the irreversible loss of its habitats and the isolation of its natural protected areas (Chebez 2005).…”

Un aporte al entendimiento de la lignificación de los pastizales/sabanas del Chaco Semiárido sudamericano

“…La lignificación junto con la conversión de ecosistemas nativos en tierras para cultivos (incluido las pasturas exóticas) fueron identificadas como las mayores causas de la desaparición de los pastizales/sabanas en la Región Chaqueña (Grau et al 2014;Fernández et al 2020). A la fecha, no existen experiencias destacadas en el campo de la restauración y el uso sustentable de estos ecosistemas.…”

“…En gran parte, ello se debería a que las políticas de conservación de la Argentina priorizan a los bosques e ignoran a los pastizales/sabanas (Grau et al 2014). En la comunidad científica, aunque se advierte un interés creciente por la problemática (Grau et al 2014;Kunst et al 2015;Fernández et al 2020), resulta insuficiente dada la gravedad de la situación. Por lo tanto, es fundamental estimular a los decisores políticos para que incluyan a los pastizales/sabanas en las políticas de conservación y uso sustentable de los ecosistemas nativos, y también a la comunidad científica para que aporte los conocimientos necesarios para una toma de decisiones eficaz (Grau et al 2014;Fernández et al 2020).…”