Quarrying impact
The quarrying environmental impact focused on the impact on vegetation
cover and the loss of Pampean grasslands (Darwish et al., 2011), was
evaluated using QGIS software and information obtained from the
Direction of Mining Cadastre of the province of Buenos Aires
(https://www.gba.gob.ar/produccion/areas_de_trabajo/mineria).
This government agency records the materials extracted from each quarry.
This information added to the degree of permeability of the rocks of the
Tandilia Mountains in each quarry site, was used to associate the type
of the extraction to the impact level. A higher level of permeability
increases the vulnerability of groundwater due to the increased passage
of water contaminated with heavy metals, other minerals, and toxic waste
(Darwish et al. 2011 and Zhang 2013).
The area of Pampean grassland affected by mining activity in each county
was estimated and it was possible to obtain a quotient indicating the
loss of native habitat due to extractive activity and its percentage.
Finally, to measure the impact of all quarries in the landscape Tandilia
Mountains, an Impact index which includes a set of qualitative
variables, was used (Soriano et al. 2015). These variables are the
extent of the impact, the periodicity, the intensity, the reversibility
of the impact, and the recoverability of the environment. Each variable
has a value according to the degree of impact on the landscape. The sum
of these values will give a level of importance to the impact, which
allows us to characterize it. There are four categories of the levels of
impact: Irrelevant (0-25), Moderate (25-50), Several (50-75) and
Critical (75-100).
RESULTS
The mining activity has increased over the years in the Tandilia
Mountains. Based on the satellite imagery, the increase is both in the
amount of area occupied by the quarries and in the amount of quarries
(Table 1, Figure 2). Some of these quarries are active, and others have
been abandoned without carrying out a mitigation plan. By visual
interpretation of satellite images, it was possible to detect that 100%
of inactive quarries are invaded and surrounded by exotic vegetation
(field corroboration showed that the main invasive exotic species wereSpartium junceum , Pinus radiata , Laurus nobilis ,Acacia melanoxylon ).
In the satellite imagery of 1996, 69 quarries were observed and for 2022
the increase was more than double: 159 quarries. The total area of
native Pampean grassland is fragmented in 1971 remnants and they cover a
surface of 116580.76 hectares, of which 6428.41 hectares are affected by
this mining activity (5.22%).
Table 2 and Figure 3 show the area affected by mining activity and the
current area of Pampean grassland in each county that comprises the
Tandilia Mountains. Olavarría and Benito Juárez are the most affected
counties: they have lost 35.41% and 12.37%, respectively, of Pampean
grassland because of the extractive activity. Balcarce and Lobería are
the counties with less percentage of habitat lost by quarrying activity
(0.35% and 0.78% respectively). Also Olavarría, is the county with the
largest number of quarries (63) followed by Tandil (31) (see Table 1).
In Olavarría most of the quarries are clay (19) and granite (18) and in
Tandil there are 9 granite quarries and one clay quarry; for the other
quarries from Tandil, there is no information on the materials they
exploit. The percentage of the area used to extract the different types
of materials in the Tandilia Mountains is shown in Figure 4. Table 2
also shows that in 2022 the number of active quarries is 71,
corresponding to 44.93% of the total.
More than 80% of the area occupied for this extractive activity is
associated with the extraction of clays, granite, and limestone. Those
are the materials with the highest permeability. Table 3 shows the value
of different variables considered to estimate the Impact index. The
result of this index was 69, which categorizes as Severe the landscape
impact of quarries. The variables Intensity of the impact, effect,
periodicity, and the moment were the top contributors to the index.
DISCUSSION
In the last 28 years, the number of quarries in the Tandilia Mountains
doubled. Likewise, the area occupied by quarries also increased, being
three times larger than in 1996. This trend towards an increase in this
extractive activity is also reflected in the mining cadastre of the
Province of Buenos Aires which shows quarries already exploited and
quarries that are being explored to start extraction works. In this
cadastre, it can be seen that the projected area to be exploited in the
future in the Tandilia mountains is 6142.66 hectares, which represents
an increase of the affected area of 95.56%.
This increase in the area and number of quarries in the Pampean
grassland indicates that quarrying activity is indeed a threat to the
conservation of the native ecosystem of the Tandilia Mountains.
Moreover, many of them are abandoned and the environmental problem
related to landscape destruction, and loss of native vegetation remains
unsolved (Chase et al., 1999; Akanwa et al., 2017). As seen in satellite
imagery from 1996 to 2022 the degradation commences through the
destruction of the natural habitat itself, followed by the sheet erosion
of the delicate soil layer resulting from the breakdown of exposed solid
rocks, and concludes with changes to biodiversity and the alteration of
the natural recolonization process: the colonization by woody invasive
species (Khater et al., 2003; Darwish et al., 2011). So the ecosystem
changes induced by the mining activity itself are multiplied by the risk
of further ecosystem deterioration in and around abandoned sites
(Darwish et al., 2011; Lake & Leishman, 2004; Xu et al., 2022). Woody
invasive species colonize relatively rapidly and hamper the
establishment of native vegetation with high conservation value, so the
abundance and richness of those native species have decreased (Pitz et
al., 2019; D’Alfonso et al., 2014 ). Moreover, less vegetation exposes
the soil to erosion, resulting in a greater loss of substrates that
enable growth. This reduces the ability of the surrounding area to
support plant life and makes it impossible for native species to
colonize the area, leading to their displacement or disappearance
(Akanwa et al., 2017; Said et al., 2016). In addition to this, there are
a large number of exploration points that, although not selected for
material extraction, still have an impact on the ecosystem.
The results show that Olavarría and Benito Juárez are the counties the
most affected, with one-third and one-sixth (respectively) of their
native habitat lost. Mainly Olavarría is an area with a strong mining
culture. This extractive activity gained strength in the 1850s when new
techniques were introduced which were the basis for the take-off of the
large-scale capitalist mode of production, forming the original capital
of numerous productive enterprises. An understanding of the different
processes that determined regional growth makes it possible to explain
the way in which the Human Society-Nature mediation took place in the
region, and clearly shows an environmental rationality based on the idea
of progress and increased productivity (Paz, 2000). This anthropic
activity, closely linked to the culture of the region, has been
maintained and increased over time, as can be seen in the amount of area
affected. On the contrary, Lobería and Balcarce are the counties with
the least habitat loss due to extractive activity, with a tiny
percentage that could indicate that they are exemplary conservation
sites for the Pampean grassland of the Tandilia Mountains. Finally,
Tandil County is another example of an attempt to conserve its native
ecosystem, with only 0.93% of habitat lost to mining activity. Due to
different social protests since 2010, there has been an environmental
protection law (Law 14.126) aiming to conserve and preserve the
integrity of the geographical, geomorphological, touristic, and urban
landscape (Grosman & Kristensen, 2012).
Inconsistency can be seen between the governmental information and the
results obtained from analyzing the materials extracted from the
quarries. These discrepancies may be due to the lack of control over the
quarry activity in Argentina, as well as a delay in the timing of
information on these activities or in the updating of government
databases. On the one hand, 52 of the quarries found by visual
interpretation are not registered in the mining cadastre of the Province
of Buenos Aires. On the other hand, according to the bibliography, the
most extracted material from quarries in the province is limestone rock,
whereas the cadastre shows that only four quarries in the entire
Tandilia Mountains extract it (3.8%). The limestone rock is used for
construction in the entire province, so urbanization and population
growth demand a hike in the extraction (Bhatnagar et al., 2014).
Although there is a low percentage of quarries dedicated to extracting
limestone rock, their exploited area is high. The same happens with iron
oxide, its extraction in the whole Tandilia Mountains is 0.9%, while
the surface area taken up by its extraction is ten times bigger. This
means that these two mining exploitations, particularly, have a
considerable impact on the Tandilia Mountains: they require a lot of
surface area, and the amount of extraction is insignificant.
The Impact index that categorized the landscape impact as Severe could
significantly affect the following environmental parameters: air
quality, noise and vibrations, soil quality, groundwater quality water
resource depletion, diversity and abundance of fauna and flora, and
habitat alteration (Soriano et al., 2015). Moreover, the most extracted
materials are the most permeable. That means that those allow access to
water possibly contaminated with heavy metals and other chemicals in the
groundwater and lead to a larger ecosystem-wide problem and human
consumption of water (Darwish et al., 2011; Milgrom, 2008). This
qualitative impact assessment is another way of showing that the threat
to the native ecosystem and the environment is significant (Duinker &
Greig, 2007).
Given that mining activity in the Tandilia System follows the global
trend of increasing surface area and poses a significant threat to the
native ecosystems on which it is developed (Akanwa et al., 2017; Howarth
& Farber, 2002; Jiya & Musa, 2012; Darwish et al., 2010; Chitade &
Katyar, 2000), we propose that ecological restoration should be included
in the extractive activity budget. This should consist, at least, of a
smoothing of the slopes with the substrate removed by the works carried
out and a spreading of native seeds of the Pampa grassland on it.
Establishing semi-natural grasslands by using seeds from wild harvesting
is an effective method to restore vegetation with high natural value,
such as Eryngium regnellii which is a key species in a possible
ecological restoration because of its great diversity of pollinating
visitors (Herrera, 2019; Scotton, 2018). This could be the
beginning of the restoration process of the area altered by the mining
activity, started by quarry companies, always advised or accompanied by
biologists specialized in ecological restoration and environmental
impact assessment.
This work has confirmed the usefulness of these tools by detecting by
visual interpretation the quarries themselves and their state of
activity and studying their evolution over time by measuring geometric
parameters. However, the lack of studies on the environmental impacts of
mining and remote sensing in the Tandilia Mountains indicates the
under-utilization of those tools in this sector. Hence, the conclusions
drawn from this study will provide enhanced resources for governments,
and decision-makers to integrate these findings into restoring
initiatives. This will, in turn, manifest the research into tangible
actions on the ground.
CONCLUSION
After this analysis, it can be concluded that mining activity in the
Tandilia Mountains is a major threat to the area, which has increased in
recent decades, and that the tendency (as at the global level) will
continue to increase. This threat involves the fragmentation and loss of
the Pampean grassland with the consequent loss of biodiversity and the
invasion of exotic plants capable of colonizing areas altered by human
activity. In addition to this, quarries produce a landscape impact that
cannot be ignored. This threat is aggravated by the lack of control by
governmental agencies, whose official data related to the number of
quarries does not coincide with the results obtained in this study.
Furthermore, despite the existence of a law that obliges the remediation
of natural areas affected by mining activity, there is no control to
ensure that this process of ecological restoration is carried out.
Quarrying operations without environmental control could affect the very
existence of ecosystems and the hydro-geological conditions of the area
to a greater extent. Therefore, extractive management plans must be
developed based on the capacity of ecosystems that support life. Our
work responds to a need to confirm the threat posed to the Pampean
grassland by this extractive activity and is the first approach to this
problem in the region. The intention is to continue analyzing the
degradation gradient associated with the quarrying activity in the
Pampean grassland remnants and the surrounding areas. This analysis has
also shown that using remotely sensed images provides data and allows
the temporal evolution of different land uses to be known, thus enabling
better management of human activities in natural systems. This is why
the visualization of remotely sensed data and its processing into maps
with software such as QGIS are used as good analytical tools to
understand the impairment of nature by human activities and to be able
to determine the magnitude or degree of the threat. Analysis of
vegetation and detection of changes in vegetation patterns are keys to
natural resource assessment and monitoring. Thus it comes as no surprise
that the detection and quantitative evaluation of green vegetation is
one of the most important applications of remote sensing for
environmental management and decision-making. These same tools could be
used by enforcement agencies to monitor threats impacting the native
ecosystem to be protected.
ACKNOWLEDGEMENTS
The authors are grateful for funding from the Universidad Nacional del
Centro de la Provincia de Buenos Aires (03-PIO-65H). We would like to
thank Felisa for their commentaries and support. I. Carabia-Sanz was
supported by fellowships from the Comisión de Investigaciones
Científicas de la Provincia de Buenos Aires (CICPBA). A. Cortelezzi,
M.V. Simoy and I Berkunsky are Research Fellows of Consejo Nacional de
Investigaciones Científicas y Técnicas de Argentina CONICET.
CONFLICT OF INTERESTS
The authors have no conflict of interest to declare.
REFERENCES
Akanwa, A. O., Okeke, F. I., Nnodu, V. C. & Iortyom, E. T. (2017).
Quarrying and its effect on vegetation cover for a sustainable
development using high-resolution satellite image and GIS.Environmental Earth Sciences, 76 , 505.
https://doi.org/10.1007/s12665-017-6844-x
Bhatnagar, D., Goyal, S., Tignath, S. & Deolia, D. K. (2014). Impact of
opencast limestone mining on groundwater in Katni river watershed,
Madhya Pradesh, India–A geoinformatics approach. Journal of
Geomatics, 8 , 101–106.
Bernaud, G. & Le Bloch, F. (1998). Entre terre et eau, agir pour les
zones humides. Dossier d’information: ministère de l’aménagement
du territoire et de l’environnement, Paris.
Bétard, F. (2013). Patch-Scale Relationships Between Geodiversity and
Biodiversity in Hard Rock Quarries: Case Study from a Disused Quartzite
Quarry in NW France. Geohéritage , 5 , 59–71.
https://doi.org/10.1007/s12371-013-0078-4
Bilenca, D. & Miñarro, F. (2004). Identificación de Áreas Valiosas de
Pastizal (AVPs) en las Pampas y Campos de Argentina, Uruguay y sur de
Brasil. Fundación Vida Silvestre, Buenos Aires.
Catastro minero de la Provincia de Buenos Aires (2023). Available:
https://www.gba.gob.ar/produccion/areas_de_trabajo/mineria [Last
time access 9/05/2023].
Cingolani, C. A. (2011). The Tandilia Mountains of Argentina as a
southern extension of the Río de la Plata craton: an overview.International Journal of Earth Sciences, 100 , 221–242.
Chandler, G., Markham, B. L. & Helder, D. L. (2009). Summary of current
radiometric calibration coefficients for Landsat MSS, TM, ETM+, and EO+1
ALI sensors. Remote sensing of environment , 113 , 893–903.
https://doi.org/10.1016/j.rse.2009.01.007
Chase, T. N., Pielke, R. A., Kittel, T. G. F., Nemani, R. R., &
Running, S. W. (1999). Simulated impacts of historical land-cover
changes on global climate in northern winter. Climate Dynamics ,16 , 93–105.
Chebez, J. C. (2005). Guía de las reservas naturales de la Argentina.