Quarrying impact
The quarrying environmental impact, focused on the impact on vegetation
cover and the loss of Highland grassland (Darwish et al., 2011), was
evaluated using QGIS software and cadastre information (Subsecretaría de
Minería, 2023). 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 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; Zhang 2013).
The area of Highland 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 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 in the area
occupied by the quarries and in the number of quarries (Table 1, Figure
2). Some of these quarries are active, and others have been abandoned
without carrying out a mitigation plan.
In the satellite imagery of 1996, 69 quarries were observed; for 2022,
the increase was more than double: 159 quarries. The total area of
native Highland grassland is fragmented in 1971 remnants, and they cover
a surface of 116580.76 ha, of which 6428.41 ha are affected by this
mining activity (5.2%).
Table 2 and Figure 3 show the area affected by mining activity and the
current Highland grassland area in each county comprising the Tandilia
Mountains. Olavarría and Benito Juárez are the most affected counties:
they have lost 35.4% and 12.4% of Highland grassland because of the
extractive activity. Balcarce and Lobería are the counties with less
percentage of habitat loss by quarrying activity (0.3% and 0.8%,
respectively). Also, Olavarría is the county with the most significant
number of quarries (63), followed by Tandil (31) (Table 1). In
Olavarría, most of the quarries are clay (19) and granite (18); in
Tandil, there are nine 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 clay, granite, and limestone extraction. Those are the
materials with the highest permeability. result of the impact index was
69, which categorizes as Severe the landscape impact of quarries (Table
3). The intensity of the impact, effect, periodicity, and moment were
the top contributing variables 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, 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 being explored to start extraction works. In this cadastre, the
projected area to be exploited in the future in the Tandilia mountains
is 6142.66 ha, representing an increase of the affected area of 95.6%.
This increase in the area and number of quarries in the Highland
grassland areas indicates that quarrying activity is indeed a threat to
the conservation of the native ecosystem of the Tandilia Mountains. The
abundance and richness of native species have decreased, with invasive
woody vegetation being the most present in the study area (D’Alfonso et
al., 2014). 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).
Active quarries in 2022 represent a relatively low percentage of the
total number of quarries: many of them are abandoned, but the
environmental problem is not solved; those related to the destruction of
the landscape, vast losses of vegetation, and the alteration of the
native ecosystem remain (Chase et al., 1999; Akanwa et al., 2017). So,
the ecosystem changes induced by the mining activity are multiplied by
the risk of further ecosystem deterioration in and around abandoned
sites (Darwish et al., 2011). All of these inactive quarries have exotic
vegetation present, and some of them are invaded by such vegetation,
which is the first with the capacity to colonize the disturbed substrate
(Lake & Leishman, 2004; Xu et al., 2022). In addition to this, many
exploration points still impact the ecosystem, although not selected for
material extraction.
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. Understanding the different
processes that determined regional growth makes it possible to explain
how the Human Society-Nature mediation took place in the region and
clearly shows an environmental rationality based on progress and
increased productivity (Paz, 2000). This anthropic activity, closely
linked to the region’s culture, has been maintained and increased over
time, as can be seen in the 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
Highland grassland of the Tandilia Mountains. Finally, Tandil County is
another example of an attempt to conserve its native ecosystem, with
only 0.9% 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 around
Tandil city only (Grosman & Kristensen, 2012).
Inconsistency can be seen between the governmental information and the
results obtained from analyzing the materials extracted from the
quarries. On the one hand, 52 of the quarries found by visual
interpretation are not registered in the Province of Buenos Aires mining
cadastre. On the other hand, according to the bibliography, limestone
rock is the most extracted material from quarries in the province. In
contrast, the cadastre shows that only four quarries in the 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 a low percentage of quarries are 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 shows that the threat to the native
ecosystem and the environment is significant (Duinker & Greig, 2007).
This work has confirmed these tools’ usefulness by visually interpreting
the quarries themselves and their state of activity and studying their
evolution over time by measuring geometric parameters. However, the need
for studies on the environmental impacts of mining and remote sensing in
the Tandilia Mountains indicates the under-utilization of those tools in
this sector.
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 Pampa 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
must be addressed. This threat is aggravated by the lack of control by
governmental agencies, whose official data related to the number of
quarries do 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 needs to be 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. This
study 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 is 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 is no surprise that
green vegetation detection and quantitative evaluation is one of the
most important applications of remote sensing for environmental
management and decision-making. Enforcement agencies could use these
same tools 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.
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.