1 INTRODUCTION
Changes in climatic conditions are periodic and common in nature in
different regions of the planet. They correspond to a natural cyclic
process involving warming, cooling and intense geological activities of
the Earth that promote various phenomena and effects, causing changes in
biological systems and ecological interrelations (Oliveira, Carneiro,
Vecchia, & Baptista, 2017). However, anthropogenic actions of the last
200 years have contributed to harmful conditions, changing particle/gas
concentrations in the atmosphere with the intensification of land use
and occupation (Oliveira et al., 2017; IPCC, 2018), and accelerating the
speed of environmental processes to the point of preventing species from
adapting or finding more suitable places to live.
The increase in the average global surface temperature is one of the
main concerns of the scientific community in view of its immediately
noticeable effects and relation with the biosphere in general. During
the last century, the increase recorded was of approximately 0.87 °C
above pre-industrial levels (IPCC, 2014) and if the temperature
continues to rise at the current rate, the increase is estimated to
reach 1.5 °C between 2030 and 2052 (IPCC, 2018). The expected average
increase in South America is 4 °C, indicating a higher frequency of
extreme events in Brazil, such as floods and heat waves (Marengo, 2005).
Regional models indicate that by the end of the 21stcentury, the most intense effects will occur in the tropical region,
specifically in the Amazon and Northeast of Brazil (Nobre, Sampaio, &
Salazar, 2008).
Climate and geological transformations have triggered adaptive processes
in biological communities, leading to their evolution, development,
diversification, dispersion and extinction throughout the history of
lineages (Costa, Veloso Filho, Aquino, & Castro, 2012). It is
particularly important to be aware of their effects on biodiversity,
because of the associated changes in distribution, phenology, migration
calendar, nesting success, and population sizes of species. Thus, the
response of biodiversity to climate change has become a very fruitful
field for research (Hughes, 2000; McCarty, 2001; Walther et al., 2002;
De Marco Junior & Siqueira, 2009; Walther, Berger, & Sykes, 2005;
Bellard, Bertelsmeier, Leadley, Thuiller, & Courchamp, 2012), including
studies with animal (Crick, 2004; Ribeiro, Sales, & Loyola, 2018;
Miranda, Imperatriz-Fonseca, & Giannini, 2019) and plant (Siqueira &
Durigan, 2007; Simões, Zappi, Costa, Oliveira, & Aona, 2019)
assemblages. Biological interaction with climate is easily observed in
geophysical patterns of vegetation distribution, reflecting different
bioclimatic zones (Salazar, Nobre, & Oyama, 2007). Within the South
American climate ranges, rainforest and savanna are the predominant
biomes. They are also largely deforested, what has led to worsening
climate change because the removal of vegetation cover promotes a warmer
and drier regional climate (Nobre et al., 2008). However, although some
evidence of current extinctions is correlated with climate change,
studies suggest that climate phenomena could outweigh habitat
destruction as the greatest global threat to biodiversity in the coming
decades (Pereira et al., 2010; Bellard et al., 2012).
Studies on Quaternary climate fluctuations and vegetation in Brazil
confirm that successive expansions and retractions occurred between
forests and savannas (Silva; Bates, 2002), the main habitat typologies
in Brazil. Cerrado is the largest forest savanna in South America,
covering 21% of the country’s land area and extending marginally into
Paraguay and Bolivia, behind only the Amazon Forest in terms of
extension (CI, 2019). Research in tropical South America has shown
Brazil as a region where significant amounts of forests are converted
into non-forest areas as a result of global warming (Ledru, 2002;
Sanaiotti, Martinelli, Victoria, Trumbore, & Camargo, 2002; Salazar et
al., 2007). Field observations and numerical models also indicate loss
of tropical forest cover (Soares-Filho et al., 2006; Vale, Cohn-Haft,
Bergen, & Pimm, 2008; Rochedo et al., 2018; Gomes, Vieira, Salomão, &
Steege, 2019), replaced by savannas (Salazar et al., 2007); this
potential reorganization of the distribution of biodiversity can affect
the structure, dynamics and functioning of ecosystems and their
respective contributions (Gallagher, Hughes, & Leishman, 2013).
Research about spatiotemporal ecological representations of species has
increased considerably in recent years with the advancement of
geoprocessing and species distribution modeling tools by ecologists and
conservation managers, and thus the need to provide efficient
assessments of these predictive models (Teles, 1996; Allouche, Tsoar, &
Kadmon, 2006). Species Distribution Models (SDMs) allow spatial
extrapolation of known occurrence records at different scales and
generate potential distribution maps based on the effects of climate
change on species distribution (Teles, 1996; Costa, Carnaval, & Toledo,
2012; Oliveira & Cassemiro, 2013).
Although the assessment of the effects of climate change on Brazilian
biodiversity is increasing in all biomes, especially those predominantly
forested and with greater species richness and endemism (Amazon and
Atlantic Forest) (Aleixo, Albernaz, Grelle, Vale, & Range, 2010), there
are few attempts to predict the impacts on non-forest areas (Siqueira &
Peterson, 2003; Terribile et al., 2012). High levels of environmental
devastation have made Cerrado to be included in the list of biodiversity
hotspots (Myers, Mittermeier, Mittermeier, Fonseca, & Kent, 2000; CI,
2019), and yet minimal (scientific and political-social) attention has
been given to the marginal and disjointed position of the savannas of
the North and Northeast, called the modern Brazilian agricultural
frontier. They refer, in large part, to “MATOPIBA”, a portion of the
North and Northeast savannas with more than 73 million hectares (8.5%
of the Brazilian territory), recognized as the portion between the
states of Maranhão, Tocantins, Piauí and Bahia (Heck & Menezes, 2016)
that accounts for much of Brazil’s grain and fiber production
(https://www.embrapa.br/tema-matopiba).
Despite its importance, there is a growing concern with maintaining
biodiversity and understanding the ecological relationships among local
species, intensified by projections of climate scenarios. In order to
strengthen conservation strategies in this ecological transition region
in central-north Brazil (from the Amazon to the Brazilian Sertão), this
research applied spatial analysis procedures and modeling tools to
predict the potential distribution of “marginal” species (on the edge
of the Cerrado biome) in this subset of priority ecotonal biodiversity
for conservation, which we are calling hereafter a sub-hotspot.
Based on the physical-environment (thematic maps) and biological
(species occurrence) variables of the current times, algorithms were
applied in order to model the fundamental niche and the potential area
of occurrence of the species. The following questions were investigated
in this study: based on the potential current occurrence range of the
target species, do the impacts of future climate change on their
distribution predict retraction or expansion of the forecasted
occurrence of the central-north peripheral Cerrado? Do predictions of
future occurrence among species of wide geographical distribution differ
from those of relatively more restricted to the northern portion of the
Biome? Are environmentally stable areas of future predicted scenarios
located inside Conservation Units (CUs) at present? In this context,
this study aimed to estimate the impact of climate change on the future
extent of occurrence of peripheral cerrados of central-north Brazil.