O2 - Using Earth Observations to Better Map Whale Presence: balancing expectations for whale conservation and shipping in the Mediterranean Sea

Lead Author: UBO

Contributors: Bénédicte Madon (UBO), Linwood Pendleton (UBO), Emiliana Valentini (ISPRA), Evangelia Drakou (University of Twente), Alessandra Nguyenxuan (ISPRA), Francesca Santoro (UNESCO), Ward Appeltans (UNESCO), Samuel Bosch (UNESCO), Pieter Provoost (UNESCO), Domingo Alcaraz-Segura (Univeristy of Grenada), Emilio Guirado (University of Grenada), Björn Alfthan (GRID ARENDAL), Levi Westerveld (GRID ARENDAL), Amber Himes-Cornell (FAO), Ana Stritih (ETH), Adrienne Gret-Regamey (ETH), Palma Blonda (CNR), Antonello Provenzale (CNR), Alex Ziemba (DELTARES), Ghada El Serafy (DELTARES), Alberto Basset (UNILE), Peter Fretwell (BAS), Hannah Cubaynes (BAS), Simone Panigada (Tethys).

The[T1] Pelagos Sanctuary for Mediterranean Marine Mammals TM is an international marine protected area (87,500 km²) between Italy, Monaco and France. It was established in 2002 to protect significant feeding and breeding habitats for the cetacean populations. Indeed, the Mediterranean Sea is home to many species of whales and dolphins which generate significant benefits for human society supporting recreational and tourist activities within the sanctuary. Meanwhile, whales and dolphins now have to share their habitat with human activities: maritime transport, military exercises, oil and gas exploration, tourism, boating, recreational activities and commercial fishing. These activities are potentially harmful to whales and dolphins. For example, overfishing leads to food scarcity and a high risk of entanglement in fishing gear, while oil and gas exploration induces high levels of underwater noise and pollution. However, the biggest concern comes from the risk of collisions with ships and boats. Sustainable ecosystem services and human well-being are strongly interconnected. As anthropogenic pressures cause threats to ecosystem integrity, functions and processes, potentially leading to loss of essential ecosystem services, there is an urgent requirement to monitor in real time the ‘where’, ‘why’ and ‘how’ of the changes. Understanding how, when and where whales and dolphins move across the Mediterranean Sea is therefore an important step towards implementing measures to protect these marine mammals and the corresponding ecosystem services.
In this context, the Pelagos storyline focuses on combining satellite imagery, in-situ observations and ecological modelling with information from whale-watching operators and shipping. The overall objective is to map ecosystem services related to whales and to develop high resolution maps of probability of whale encounters using all available data sources. This kind of information will help decision makers identify high-priority areas for both marine mammals and human activities.

Step 1- Understanding human activities
Engagement with local experts
To develop the storyline and get a good overview of all the available information, data and experience of the experts working in the area since its creation, a scoping meeting was organized in February 2016. The aim of this meeting was to create a roadmap for developing a system to use remote sensing and in situ data to improve the assessment and monitoring of ecosystem services provided by whales and other cetaceans in the Mediterranean. This meeting brought together field experts and ecosystem modelers of the Mediterranean and in particular the Pelagos sanctuary with the ECOPOTENTIAL team to discuss potential synergies and paths of collaboration under the project framework. The output of this meeting was the first mind map of the Pelagos storyline (Figure 1) which was used a basis for the development of the work.

(Update March 18th 2019)

Figure 1. Mind map of the Pelagos storyline

Mapping human activities
The work within the Pelagos storyline consisted, in a second phase, in gathering relevant data on human activities. These mainly relate to whale-watching and shipping. For the whale-watching activity there was no available official data, henceforth a participatory mapping workshop took place in November 2016, hosted by Simone Panigada and Giuseppe Notarbartolo di Sciara from Tethys, to work with the area experts, whale-watching companies and associated stakeholders to map human activities in the area taking into consideration whale watching activities (Fig.2).

Fig.2- Map of whale watching activities developed during the 2016-participatory-mapping workshop.

Another type of activity had to do with the shipping activity in the area. Marine mammals in the sanctuary have to co-exist with very high and increasing levels of human activity, including some of the busiest marine traffic in the world (Fig. 3).

Fig.3- Ship traffic intensity in the Pelagos sanctuary.

Step 2- Understanding whale distribution
By gathering in-situ and remote-sensing data on whale presence
Researchers and nongovernmental organizations use boat and aerial surveys to collect data on marine mammal species presence that is spatially referenced and centralized in an online database, OBIS-SEAMAP (Fig.4).

Fig.4- Sighting records of 3 species of whales inside the Pelagos Sanctuary, the fin whale (Balaenoptera physalus), sperm whale (Physeter macrocephalus) and Cuvier’s beaked whale (Ziphius cavirostris) in the Pelagos Sanctuary. Source: OBIS Seamap.

Until a few years ago, monitoring individual animals from satellites was not even conceivable. With partners from the British Antarctic Survey (Hannah Cubaynes and Peter Fretwell) and from the University of Grenada (Emilio Guirado and Domingo Alcaraz-Segura), ECOPOTENTIAL is applying very high-resolution satellite imagery to find fin whales from space. (Fig.5).

Fig.5- Automatic whale-counting procedure from very high-resolution satellite imagery (Guirado et al., 2019)

We started exploring ways to extract whale and dolphin presence information through photos available on social networks: we wanted dates and geo-locations (metadata of the photos). This initiative was part of challenge submitted for a Hackathon that took place in Brest on October 2017.
Finally, we are developing field sampling protocols based on environmental DNA to gather an innovative and promising data kind on whale presence to support MPA management.

By modelling whale distribution
A second phase of the storyline aims at addressing whale mobility, feeding habitat and traveling pathways and using ecological modelling to predict whale presence using relevant proxies such as Chlorophyll-a. Patterns of selected environmental variables (e.g. chlorophyll-a fronts and concentration) are thought to be explanatory (or proxy) variables for some whale population presence (Fig.6).

Fig.6- Results of ecological modelling to estimate feeding habitat suitability for fin whales based on Chl-a concentration.

A trend map for fin whale feeding habitat in the Mediterranean Sea between 2003 and 2016 was produced showing that the central and south-eastern areas had a positive trend (from 1 to 10% per decade) while the north-eastern and western parts showed negative trends (Fig.7). Globally, an increase of chlorophyll-a fronts was observed during summer in relatively poor waters in terms of productivity likely due to unusual wind events and increased evaporation.

Fig.7- Trend map of fin whale feeding habitat distribution between 2003 and 2016.

Localized hot spots of primary productivity act as attractors for marine mammals and a mosaic of productivity locations can help to predict, combined with temperature, the distribution of potential whale feeding areas. Fin whales, for example, are mostly sighted off the continental shelf near chlorophyll-a fronts with low concentrations (<0.5mg/m³). Chlorophyll-a fronts are highly dynamic features that have shown to be hotspots of marine productivity if they remain long enough (weeks to months) to efficiently transfer the energy in marine food webs through zooplankton growth and to attract higher trophic levels (Panigada et al., 2017). Combined with the satellite tracking data of fin whales in the Mediterranean Sea from Panigada et al. (2017), our aim is to link fin whale behavior (using 2 behavioral categories: feeding or travelling) to Chlorophyll concentration. Results of these analysis could help better manage optimal ship routes through the use of tools such as VISIR (Mannarini et al., 2016).

By using future projections
Based on the data in OBIS, we created a current climate distribution model for fin whales in and around the Pelagos Sanctuary based on sea surface temperature, chlorophyll a fronts and bathymetry (Fig.8). A future climate model was also created using the RCP 4.5 projections for the year 2050. Results indicate that the predicted suitable area strongly decreases by 2050 (Fig.9).

Fig.8- Current habitat suitability for fin whales.

Fig.9- Future habitat suitability in 2050.

Step 3- Bringing everything together
Understanding the human-whale interactions within the sanctuary led to the development of a Bayesian Belief Network model to map the probability of perceiving societal benefits from nature based on the probability of encounters between humans and society through whale-watching. This network used input data from the probabilistic modelling of whale presence based on their feeding habitat as well as data from the participatory mapping workshop on the location of whale-watching activities. It also overlaid this data with the remote sensing data in which species detection was measured. This work shed light on the need to improve the maps of whale distribution.

Fig.10. BBN Model for the Pelagos Sanctuary cultural ES

The final work on the Pelagos storyline consists therefore, in an effort to integrate all available data on whale presence in a data cube (Fig.11) using data assimilation techniques to fill each cell of the cube to produce more accurate maps of encounter probability with whales.

Fig.11 – Conceptual visualization of the Whale Data Cube.

References:
Guirado, E., Tabik, S., Rivas, M.L., Alcaraz-Segura, D., and F. Herrera. 2019. Automatic whale counting in satellite images with deep learning. In Review in PlosOne.
Mannarini, G., Pinardi, N., Coppini, G., Oddo, P., and Iafrati, A.: VISIR-I: small vessels – least-time nautical routes using wave forecasts, Geosci. Model Dev., 9, 1597-1625, doi:10.5194/gmd-9-1597-2016, 2016.
Panigada, S., Donovan, G. P., Druon, J. N., Lauriano, G., Pierantonio, N., Pirotta, E., ... & Sciara, G. N. (2017). Satellite tagging of Mediterranean fin whales: working towards the identification of critical habitats and the focusing of mitigation.

Click here to download the storyline presentation

Last update: May, 2019