Research Article |
Corresponding author: Sylvain Moulherat ( sylvain.moulherat@terroiko.fr ) Academic editor: Cristian-Remus Papp
© 2024 Sylvain Moulherat, Léa Pautrel, Guillaume Debat, Marie-Pierre Etienne, Lucie Gendron, Nicolas Hautière, Jean-Philippe Tarel, Guillaume Testud, Olivier Gimenez.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Moulherat S, Pautrel L, Debat G, Etienne M-P, Gendron L, Hautière N, Tarel J-P, Testud G, Gimenez O (2024) Biodiversity monitoring with intelligent sensors: An integrated pipeline for mitigating animal-vehicle collisions. In: Papp C-R, Seiler A, Bhardwaj M, François D, Dostál I (Eds) Connecting people, connecting landscapes. Nature Conservation 57: 103-124. https://doi.org/10.3897/natureconservation.57.108950
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Transports of people and goods contribute to the ongoing 6th mass extinction of species. They impact species viability by reducing the availability of suitable habitat, by limiting connectivity between suitable patches, and by increasing direct mortality due to collisions with vehicles. Not only does it represent a threat for some species conservation capabilities, but animal vehicle collisions (AVC) is also a threat for human safety and security in transport and has a massive cost for transport infrastructure (TI) managers and users. Using the opportunities offered by the increasing number of sensors embedded into TI and the development of their digital twins, we developed a framework aiming at managing AVC by mapping the collision risk between trains and ungulates (roe deer and wild boar) thanks to the deployment of a camera trap network. The proposed framework uses population dynamic simulations to identify collision hotspots and assist with the design of sensors deployment. Once sensors are deployed, the data collected, here photos, are processed through deep learning to detect and identify species at the TI vicinity. Then, the processed data are fed to an abundance model able to map species relative abundance around the TI as a proxy of the collision risk. We implement the framework on an actual section of railway in south-western France benefiting from a mitigation and monitoring strategy. The implementation thus highlighted the technical and fundamental requirements to effectively mainstream biodiversity concerns in the TI digital twins. This would contribute to the AVC management in autonomous vehicles thanks to connected TI.
Abundance modelling, animal vehicle collision, autonomous vehicle, camera traps, computer vision, connected transport infrastructure, deep learning, digital twin, risk management, ungulates
Transports of people and goods contribute to the ongoing 6th mass extinction of species (
Not only do they represent a threat for some species conservation capabilities, animal vehicle collisions (AVC) are also a threat for human safety and security in transport when large species are involved. Animal vehicle collisions’ events also represent a massive cost for TI managers and users due to infrastructure and vehicle repair or compensations for damages (
In Europe, terrestrial AVC often involve large mammals (
The transport system is in a deep digital transformation with the development and deployment of data-driven TI management (
Unfortunately, biodiversity concerns are not yet part of this TI digital environment which nevertheless offers a suitable place for biodiversity-based risk management such as AVC (
With the OCAPI initiative, the goal is to enhance the integration of biodiversity-oriented digital facilities into the DT of TI (
The methodological framework developed and implemented in this study is composed of 5 major steps (Fig.
Framework to deploy sensors along a transport infrastructure to map the animal abundance in the transport infrastructure vicinity in order to manage the animal vehicle collision risk.
The study site is a 19.7 km section of the railway joining Toulouse to Agen in south-western France (Fig.
Study site in south-western France focused on 19.7 km of railway where numerous AVC occurred the last 10 years. The land cover is represented using the 5 main habitat typologies as used for the statistical analysis. Camera traps deployed on the field are identified by a letter from A to L.
The study site benefits from a land use map produced by combining data from Corine Land Cover (
As a part of the AVC hotspot identification, we used SimOïko to perform spatially explicit population dynamic simulation of ungulates on the study site. SimOïko is an individual-based spatially explicit model developed to perform population viability analysis based on the MetaConnect model (Moulherat, 2014). In the model, each individual of the simulated population is a unique agent whose virtual life is driven by stochastic processes. For example, survival of an individual depends on the result of a Bernoulli event with probability p corresponding to the average survival of the individual age class. The model assumes that individuals live in panmictic patches of suitable habitat. In this study, roe deer and wild boar, the AVC target species, are not explicitly modelled. Instead for the sake of simplicity, we used a virtual species representative of a mixture of roe deer and wild boar life history traits (
We modelled the dispersal behaviour of ungulate moving between suitable habitat patches using the SimOïko embedded Stochastic Movement Simulator (SMS) algorithm (
Simulations were initialised with 118 individuals assuming that all the potential suitable patches are occupied at their maximum carrying capacity. The simulation runs for 100 years which is sufficient to ensure the metapopulation dynamic stabilisation for at least the last 50 years (see Suppl. material
As a result, the model provides the expected number of individuals living in the studied landscape and a map of the cumulative number of animal passage per map pixel during the simulation time (
To map the abundance of ungulate in the TI vicinity using the camera traps deployed for another purpose (e.g. evaluate the mitigation measures efficiency), we mimic the expected monitoring process and analysis to evaluate its effectiveness in an iterative four-step process:
On the study site, we designed a monitoring program to evaluate the efficiency of 2 bridges upgrades (including fencing) (sectors 1 and 2 Fig.
The monitoring began in August 2022. However, due to TI manager investment abilities, the monitoring could only start for the two bridges upgrading reducing the study site section to 11.7 km- long for the framework showcasing (sectors 1 and 2 Fig.
Both scenarios of camera trap deployment (SCо and SCа) were evaluated for their expected ability to provide relevant mapping of ungulate abundance close to the TI.
We used the simulated frequentation map to mimic a camera trap survey leading to a frequentation history of 30 recording occasions. Thus, for each sampling occasion, the number of detections in a pixel containing a camera trap is simulated as a random event following a Poisson distribution. The average value of this distribution corresponds to the average number of passages of ungulates within the pixel during a single time-step of the population dynamics simulation. In this respect, we divided the average number of passages of dispersing individuals by the proportion of dispersing individuals.
To recognise the main species (here roe deer and wild boar) involved in AVC on the images produced by the monitoring program, we used the YoloV8 deep neural network (
The project data set is composed of 40 358 images provided by 41 data providers across France and annotated by 51 experts thanks to the project’s collaborative annotation platform (www.ocapi.terroiko.fr). This data set was completed by the images of the COCO data set containing animals or vehicles. Annotations consist in bounding boxes drawn on the pictures and labelled with the name provided by the French national taxonomic referential (
Here we used the photos taken from 29 August 2022 to 16 April 2023 (33 weeks) for 11 sites, and from 24 October 2022 to 16 April 2023 (25 weeks) for the site E to test the framework in real conditions. The local hunter association made simple annotations by identifying the species seen on the pictures (no bounding boxes) using 3 classes labelling system: ungulate (roe deer and wild boar), human/vehicle and other, including any other species and the empty pictures. The data set thus produced is then called the showcase data set. When observations were closer than three minutes apart, only the first observation was kept as the camera-trap was likely triggered several times by the same individual (
In this paper, we do not aim to estimate the absolute ungulate abundance within the study site, but rather spatially estimate their relative abundance to identify the places with higher collision risks. To do so, we used the N-mixture model proposed by
To test the monitoring design efficiency, we compared the normalised simulated spatial pattern of ungulate movements with the normalised abundance predicted by two models using different covariates. The first model (Mod1) is built with a single site covariate: the sum of the movements in the cell during all time-steps of all repetitions. The number of sensors per cell is also used as detection covariate in Mod1. The second model (Mod2) is based on ecological covariate rather than population dynamic simulation output. Mod2 used several spatial covariates extracted from the land use map:
We performed a PCA with the areas of agriculture, forest, urban, water per cell to reduce the number of variables explaining landscape variability in the area while managing the correlation between variables (
The simulation process aiming at mimicking the camera trap survey under the SCо scenario is composed of 27 sites with 1 to 3 camera per site. The average detection per sampling occasion is of 21.2 occurrences (ranging from 0 to 90 occurrences).
Considering the SCа scenario, based on 12 sites with a single camera, the average detection per sampling occasion is 11.5 occurrences (ranging from 0 to 29 occurrences). With both scenarios, all sites benefit from at least one detection.
The sampling effectively catches most of the overall simulated movement patterns, both with the expected (SCо) and actual (SCа) sampling (Fig.
Normalised relative abundance of ungulates per 3.5 ha cell simulated by the population dynamic model (panels A and B), the Mod1 abundance model (panels C and D) and the Mod2 model (panels E and F) for SCo (panels A, C and E) and SCа (panels B, D and F). For comparison purposes, the normalisation was performed by normalising each cell of a map by the 97.5 percentile value. Regardless of the abundance modelling scenario, the sampling scenarios are expected to be able to identify relatively the riskiest sectors.
On the OCAPI data set, the mAP@0.5 metric (mean average precision when the intersection over union (IoU) (
Classification model performance. The precision reflects the model ability to limit the false positives’ prediction while the recall corresponds to its capability to avoid false negatives.
Validation data set | Test data set | |||||
---|---|---|---|---|---|---|
Number of annotations | Precision (%) | Recall (%) | Number of annotations | Precision (%) | Recall (%) | |
Roe deer | 93 | 92.47 | 79.63 | 212 | 74.06 | 83.51 |
Wild boar | 352 | 93.18 | 90.11 | 24 | 79.17 | 19.39 |
Considering the showcase data set, with 80.8% of good classification when an ungulate is actually present on the pictures (Fig.
Comparison between prediction made by the model and the actual annotations performed by the local hunter association on the showcase data set. Pictures containing roe deer or wild boar are grouped as ungulates. Similarly, the predicted “Other” class merges boxes with other animals and empty pictures. Thus, the model predictions are presented under a form comparable to the one used by the hunter association. Details of the showcase data set processing results are developed in Suppl. material
Mod2, implemented on the data issuing from the available 33 weeks monitoring program, results in ungulates concentrated along the two rivers crossed by the railway and in the Bouconne forest in the western part of the site (Fig.
In this paper, we associated methods from ecology, data science and engineering to develop a 5-steps framework for AVC management on a linear transport infrastructure (Fig.
We implemented the framework for an existing TI benefiting from a specific monitoring program. Because biodiversity monitoring is not the central job of TI managers, we can hardly expect that they would deploy a sensor network specific for that purpose. Thus, our framework was developed to be conveniently part of an existing network dedicated to other goals (here evaluating the mitigation measures efficiency). However, steps 1 to 3 (the sensor-based monitoring design phase) may be part of the TI conception phases and particularly contribute to environmental impact assessment. Indeed, population modelling is increasingly used for decision making including an environmental impact assessment (
If using existing cameras around the TI or embedding ones dedicated to biodiversity monitoring may contribute to map the AVC risk, their deployment must be optimised to ensure the system cost efficiency as well as its sustainability (
The recognition algorithm fine-tuned in this work is not general enough to properly perform in operative conditions. The moderate performances of the model are due to multiple factors such as the number of annotated data used to train the model and particularly the lack of pictures taken in operative-like conditions. To improve these performances, we successfully used DeepFaune which was trained on larger data set to recognise our focal species among other French common ones (
As sensors collect data continuously, our framework could possibly be improved by using abundance or occupancy models in continuous-time (
Digital twins are developing regardless of the TI type (e.g. road, railway, airport, etc) and the framework we proposed can be applied to any type of TI with, for instance, some adaptation for bird detection in a 3D explicit digital environment to manage collisions with planes (
We thank SNCF Réseau for having let us use their railway network to perform this work as well as granting the preliminary works and the ongoing monitoring. We warmly acknowledge all the data providers who allowed us to train the deep learning algorithms, especially Vinci Group and the Réseau Loup Lynx who provided very large data sets.
The authors have declared that no competing interests exist.
No ethical statement was reported.
The OCAPI project has been funded by the FEREC foundation. This work is also part of the PSI-BIOM project granted by the French PIA 3 under grant number 2182D0406-A and the AIGLE project granted by the French National Research Agency. LP benefits from a French government ‘’Cifre’’ grants for PhD students.
SM and LP mainly wrote the manuscript, SM performed the simulations, LP, GD, GT, JPT trained the deep learning algorithms, SM, LP, MPE and OG performed the analysis, LG digitised the land cover, SM, NH, JPT and OG conceptualised the paper, SM, JPT and OG obtained the grant. All the authors contributed to the paper edition and approved the final version.
Sylvain Moulherat https://orcid.org/0000-0003-2451-018X
Léa Pautrel https://orcid.org/0009-0007-4266-1703
Marie-Pierre Etienne https://orcid.org/0000-0002-2097-2267
Lucie Gendron https://orcid.org/0000-0003-0777-3359
Nicolas Hautière https://orcid.org/0000-0002-4885-5919
Jean-Philippe Tarel https://orcid.org/0000-0002-9241-5347
Guillaume Testud https://orcid.org/0000-0001-7759-3017
Olivier Gimenez https://orcid.org/0000-0001-7001-5142
All of the data that support the findings of this study are available in the main text or Supplementary Information.
Complementary details of the methods used in the paper as well as additional results
Data type: docx
Explanation note: All the source data and code that can be shared and are available on an online repository at https://oikolab.terroiko.fr/publications/monitoring-and-animal-vehicle-collisions-nat-conserv-2024 . For data with restricted access, the supplementary material explains how to access them on demand.