Southeastern South America contains one of the vastest networks of grasslands in the Neotropics. The grassland biome in Argentina originally comprised a vast mosaic of temperate steppes (pampas) and subtropical savannas (campos) spread across several major flood-plains (Krapovickas and Di Giacomo 1998). These grassland regions are a globally important centre of endemism for numerous species of fauna and flora (Krapovickas and Di Giacomo 1998, Stattersfield et al. 1998). About 60 grassland-dependent bird species occur in Argentina (Krapovickas and Di Giacomo 1998), and three Important Bird Areas (IBAs) have been identified in the grasslands. However, these grasslands are also very suitable for agriculture and livestock, and as a result are probably the most threatened terrestrial biome in Argentina (Krapovickas and Di Giacomo 1998, 2000).

Native Argentinian grassland has been intensively converted to short-grass matrix for livestock grazing. This has been the most prominent driver in the 2,762km² (13%) reduction of this habitat type from 1974 to 2011 in the Buenos Aires province alone (total of 21,911km²). During the same timeframe, short-grass matrix increased by 5,180km², representing almost a quarter of the land in the study area (Lara and Gandini 2014). Countrywide, the great majority of grassland has already been converted to cropland, rangeland, or settlement—with an average of 39% of pampas grassland being converted to cropland by 2002 (Minarro and Bilenca 2008). Less than 3% of the original pampas remain in a natural state (Roman 2000) and the area covered by grassland has been decreasing annually by 0.5% between 1988 and 2002 (Paruelo et al. 2005). Additionally, grasslands in Argentina are periodically burnt to produce short-term increases in the land’s productivity, further fragmenting the available grassland for birds and other biodiversity (Nabinger et al. 2013).

Grassland birds depend on large patches of connected grassland for food and nesting (Pretelli et al. 2013). Therefore, the degradation and fragmentation of this habitat in southeastern South America has led to marked declines in these species. It has also contributed towards reduced reproductive performance and increased brood parasitism in Brown-and-yellow Marshbirds and reduced nesting success in Spectacled Tyrants (Pretelli et al. 2015). While livestock farming is the dominant cause for grassland conversion in the area, urbanisation reduces the density and abundance of grassland bird species as well (McLaughlin et al. 2014). Marshbird nesting success was 62% reduced in agricultural-livestock converted patches compared to native grassland within Mar Chiquita Coastal Lagoon Biosphere Reserve, and Spectacled Tyrants had 84.4% and 86.4% reduced success in agricultural-livestock and urban patches compared to within the reserve (Pretelli et al. 2015). The decline in abundance of unthreatened birds like the Marshbird due to conversion of grassland to cropland or pasture (Codesido et al. 2011) is a troubling sign for more vulnerable threatened species, such as the Strange-tailed Tyrant Alectrurus risora pictured above.

The remaining large blocks of once open and tree-less grasslands are being afforested with plantations of trees, usually non-native species of pine and eucalyptus (Krapovickas and Di Giacomo 1998), following land preparation that often involves road building and wetland drainage (Di Giacomo and Krapovickas 2001). Between 1995 and 2000, the area of such monocultures increased by more than 500% (Di Giacomo and Krapovickas (2001), with over 1,000 km² of grassland converted to plantations in 2001 alone (Laura 2002). Several potential grassland IBAs have already been destroyed, before their importance could be confirmed (Di Giacomo and Krapovickas 2001). Moreover, the negative impacts of tree plantations on grassland ecosystems can extend well beyond the actual converted habitat, for example through edge effects caused by road building (O’Leary and Nyberg 2000) and through increased densities of non-grassland predators (Herkert et al. 2003). Recognising the immediate need for landscape planning and conservation, BirdLife International’s partners Aves Argentinas-AOP, SAVE Brasil, Aves Uruguay, and Guyra Paraguay founded the Alianza del Pastizal with the aim of promoting sustainable cattle rearing through nature conservation-agricultural production integration.