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Evaluating ecological restoration success by mapping regulating ecosystem services based on field and remote sensing approaches: a case study in Arrábida Natural Park
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Resumo(s)
Regulating ecosystem services (ES) are important for sustaining life on Earth, as they maintain
the integrity of ecosystems and benefit human well-being. However, anthropogenic activities like
quarrying put these services under great pressure by reducing biodiversity and extensively damaging
the soil. Thus, restoration actions are necessary to recover these highly degraded areas and the ES they
provide, and are one of the main focuses of the current “Decade on Ecosystem Restoration (2021-2023)”
declared by the United Nations. However, the success of most restoration interventions remains
unknown or is typically assessed solely through spatially-limited local approaches e.g. field sampling.
In contrast, remote sensing (RS) repeatedly records and assesses changes in ecosystem characteristics
at different spatial (and temporal) scales and can be combined with field data to produce valuable
models and maps for large areas that can support adaptive management decisions.
This dissertation aimed to evaluate the success of the ecological restoration of a quarry located
within the Arrábida Natural Park, a protected area in Portugal with a high ecological value that served
as this study's reference ecosystem. For this, field and RS data were combined to assess key ecosystem
attributes which are closely linked with several ES. Furthermore, field and RS data were used to analyse
the trajectory over time (based on a chronosequence) and evaluate the restoration success through
statistical analysis, modelling, and mapping of the ecosystem attributes. The restoration intervention
mode applied in each site was also taken into consideration.
Overall, ecosystem recovery in the SECIL-Outão quarry was incomplete. Most studied attributes
and associated ES did not resemble or had values below those of the reference ecosystem (e.g. soil
carbon sequestration, soil fertility, habitat quality, resilience to fire and drought). Moreover, the
hypothesis that older restored quarry areas would be closer than recent ones to providing the same
regulating ES as the reference ecosystem was only observed for some attributes. Additionally, the
recovery trajectory differed between ecosystem attributes. While some variables showed positive signs
of improvement with restoration age (e.g. seedling density), the majority showed a stabilisation 15-20
years after restoration (e.g. productivity, soil decomposition, species similarity with the reference
ecosystem). Furthermore, there was a decrease over time in several ecosystem functioning indicators,
which might negatively affect the restored ecosystem’s functioning and resilience.
In the older plantations at the limestone benches, pine cover seems to contribute to slow
decomposition rates and decreased functional diversity, which might negatively affect ecosystem
functioning and the quality of ES. This indicates limitations in the restored ecosystem, possibly due to
the high competition and exhaustion of limited resources caused by the high Aleppo pine cover in the
older restored areas. Furthermore, ecosystem resilience variables were negatively affected by pine
cover, such as the proportion of resprouters (resilient to fire) or sclerophyll vegetation (resilient to
drought). This tendency is particularly worrying in a climate change scenario, where higher fire
frequency and severe droughts are expected. The pollination service estimated through flowering
duration and entomophily was also negatively affected by pine cover.
Thus, older restored sites might be in a vulnerable state due to their decreasing resilience and
pollination services, which could jeopardise restoration efforts in case of future disturbances, calling
the need for adaptive management actions. Since the high pine cover became an obstacle to the
progression of the plant community in the direction of the reference system, pine thinning is highly
recommended to promote key functional traits and ecosystem functioning, resilience, and biotic fluxes.On the other hand, shrub density in the restored sites proved to be very important in increasing
species similarity with the reference ecosystem, taxonomic and functional diversity, and seedling
density. Therefore, these results emphasise the importance of using native shrub species in the recovery
of the quarry locations. Additionally, interventions that promote higher native shrub densities are highly
suggested to improve the functioning, resilience, and self-maintenance of the restored areas, especially
in the hydroseeded slopes where herbaceous cover is dominant and similarity to the reference is low.
Furthermore, the produced maps provided estimates for the spatial distribution of several
ecological variables and ES, indicating which areas are more in need of adaptive management actions.
Their estimates were overall comparable with the statistical analysis of the different intervention modes
and the recovery success index calculated for each ecosystem attribute (which considered the different
intervention modes and zone types). Therefore, the multiple maps created by statistical models
supported the hypothesis that RS data, together with field data, allow upscaling information and the
creation of valuable models that can be used to produce spatial information at the landscape scale.
In conclusion, this study found that the restored ecosystem differs from its reference model and
the ES it provides, even after 30 years of restoration. Furthermore, these findings endorse the idea that
ecological restoration should not be viewed as a substitute for conservation, nor should the promise of
restoration be used to justify further destruction or unsustainable use, as restoration may not succeed in
re-establishing the full assemblage of native species or the full extent of the original ecosystem’s
structure and function.
Descrição
Tese de mestrado, Biologia dos Recursos Vegetais , 2023, Universidade de Lisboa, Faculdade de Ciências
Palavras-chave
Restauro ecológico de pedreiras serviços de ecossistema de regulação deteção remota atributos funcionais Parque Natural da Arrábida Teses de mestrado - 2024