Acoustic habitat degradation and its containment

Underwater Domain Awareness

Dr Cdr Arnab Das, examines the deadly conflict between humans and marine mammals in the Indian Ocean Region, and proposes a new framework for a solution

The 21st century is witnessing a massive maritime push in the Indian Ocean Region (IOR). The region, with its tropical littoral, faces unique challenges in terms of optimal sonar performance for acoustic surveys. The IOR also has socio-economic challenges, given its developing nations with pre-modern governance structures. Marine environment conservation initiatives also have to compete with budgetary demands related to security, the blue economy, disaster management and science and technology.

The conflict

Whales are particularly susceptible to disorientation as the result of the acoustic degradation that is occurring largely as a result of increased shipping traffic.
Whales are particularly susceptible to disorientation as the result of the acoustic degradation that is occurring largely as a result of increased shipping traffic. Photo: NOAA / PD. Montage: Louis Mackay

Marine environmental conservation is extremely resource-intensive. Political leaderships often fail to prioritise these concerns over socio-economic ones, and in the post-Covid-19 world it may be impossible to allocate more funds for environment-related issues. There is going to be a double whammy: on the one hand, the blue economy has to provide as many growth opportunities as possible; on the other, the allocation of R&D funds to create greater sustainability is going to meet greater resistance. So, given the unique challenges in the new global order, a unique framework is required to help end the increasing acoustic habitat degradation (AHD) in the region.

Marine species – mammals in particular – use sound for biologically critical functions, including foraging, navigation, communication and finding mates. The increasing shipping traffic that reflects the expansion of global trade generates a serious increase in the low-frequency ambient noise in the ocean. That increase has been recorded at 3dB (that is, doubling) per decade since the 1950s. The sounds emitted by marine mammals, especially the big whales, are masked by shipping noise, due to overlapping spectral bands. This leads to disorientation which can easily end in whale fatalities.

Shipping traffic has four unique characteristics that makes it a significant source of AHD for marine mammals:

  • It is the sole ubiquitous source of ambient noise in the ocean.
  • The low frequencies of this noise undergo minimal attenuation in the underwater medium, and therefore influence a much bigger area than the sounds made by cetaceans. The wide distribution of shipping traffic ensures an almost uniform spread of the AHD across the world’s oceans.
  • The slow and steady increase in shipping traffic and in the resultant underwater noise makes the assessment and regulation of its impact extremely difficult.
  • Shipping traffic is directly linked to global trade and economic growth, so regulation of developing nations’ shipping traffic is politically problematic. Shipping noise, a transborder phenomenon, cannot be regulated without the support of the nations in the region; and in the IOR the regional frameworks are extremely sensitive.

The IOR comprises developing nations with competing political agendas and priorities. The diversity of these nations in terms of their socio-economic status and their science and technology resources further erodes the possibility of an effective regional framework. The use of sonars in the absence of any local site-specific algorithm development is seriously harmful, and the IOR’s tropical littoral waters, with their random fluctuations of the underwater medium, limit sonar performance. Moreover, indigenous research and development, besides being highly resource-intensive, require long-term sustained efforts. These in turn demand strong political backing with nuanced policy support, funding for technology and innovation initiatives, and participation by academia for effective human resource development.

Infrastructure and security

Figure 1. Recent marine mammal strandings along the Indian coast. Upper left: a 42-foot blue whale stranded off the Alibag coast (Maharashtra) in June 2015. Upper right: a 50-foot Bryde’s whale stranded near Mumbai in January 2016. Below: some of the over 90 short-finned pilot whales stranded at Tuticorin (Tamil Nadu) in January 2016.
Figure 1. Recent marine mammal strandings along the Indian coast. Upper left: a 42-foot blue whale stranded off the Alibag coast (Maharashtra) in June 2015. Upper right: a 50-foot Bryde’s whale stranded near Mumbai in January 2016. Below: some of the over 90 short-finned pilot whales stranded at Tuticorin (Tamil Nadu) in January 2016. Photo: CC-BY-3.0

Major maritime infrastructure development in the IOR spans the security apparatus, blue economic entities, environmental regulators, disaster management authorities, and science and technology providers. The government of India has declared the Security and Growth for All in the Region (SAGAR) vision as its policy for the IOR, and projected a leadership role for itself in it. SAGAR recognises both the security concerns that exist in the region and its as yet unexplored and unexploited growth potential. The Indian government has initiated several mega-projects to capitalise on the IOR’s maritime potential, including the Sagarmala (multi-modal transport corridors with effective last-mile connectivity) and the Inland Water Transport project. There has been significant policy and funding support to ensure public and private participation in all these initiatives. India has also been a committed participant in the global efforts to tackle the high levels of piracy off the Somalian coast.

In the absence of nuanced environmental monitoring and regulations, however, the massive increase in maritime activity in the IOR, and the resulting severe acoustic habitat degradation, have become a cause of concern. The issue has been manifested in multiple big whale stranding incidents. Figure 1 illustrates three recent incidents resulting from navigation failure due to disorientation caused by loud ambient noise. The first two cases were investigated by the author, and are attributable to anti-piracy measures since 2009. Shipping lanes were shifted towards the coast, with increased naval patrols and a bunching of shipping traffic. The ever more intense low-frequency ambient noise levels altered the migration patterns of the big whales and seriously disrupted their habitat.

A solution

The Underwater Domain Awareness (UDA) framework proposed by the Maritime Research Centre (MRC), Pune, in partnership with M/S NirDhwani Technology Pvt Ltd (NDT) can help resolve the issues discussed above and could potentially facilitate a safe, secure, sustainable growth model for all in the region and beyond. A UDA framework will encourage pooling of resources and synergising of efforts by all stakeholders within the nation and across the region. The concept of UDA, in a more specific sense, reflects our eagerness to know more of what is happening beneath the surface of our maritime domains. From the security perspective, this attention on undersea awareness will help us defend our sea lines of communication, coastal waters and varied maritime assets against the proliferation of submarines and mines. In addition, the earth’s undersea geophysical activities are highly relevant to the wellbeing of humankind, so monitoring them could provide vital clues to help minimise the impact of natural disasters.

Commercial operators in the undersea realm need accurate information on the availability of resources in order to explore and exploit them effectively for economic gain. Regulators need to know the patterns of exploitation in order to implement a sustainable plan. Scientists and researchers need constantly to improve their knowledge of, and access to, the manifold aspects of the undersea domain. With so many activities, both commercial and military, involving the ocean, there is a significant impact on the environment. So any conservation initiative needs to assess accurately the habitat degradation and species vulnerability it causes, as well as the status of the ecosystem.

A way forward

Figure 2. A visual perspective of the UDA framework model.
Figure 2. A visual perspective of the UDA framework model.

Figure 2 represents a comprehensive perspective of UDA. The underlying requirement for all stakeholders is to become aware of the developments in the undersea domain, to make sense of them, and to respond effectively and efficiently to predicted adverse consequences before they are realised.

The UDA needs to be understood in its horizontal and vertical dimensions. The horizontal is its resources: technology, infrastructure, capability and the capacity of stakeholders and others. The stakeholders, represented by the four faces of the cube, will have their specific requirements; however, the core of the cube is the region’s acoustic capacity and capability. The vertical dimension is the hierarchy of a comprehensive UDA. The base level is the sensing of the undersea domain for threats, resources and activities. The second level is the analysis of the collected data in the planning of security strategies, conservation and resource use. The top level is the formulation and monitoring of the regulatory framework at local, national and global levels.

The figure illustrates a comprehensive way forward for stakeholders to engage and interact in. The individual cubes represent the specific aspects that need to be addressed. The partnership embracing user, academia and industry can be tailored according to the given user requirements, academic input and industry interface. The construct as a whole will facilitate a more focused approach and a better-defined interactive framework. Given the appropriate impetus, the UDA framework can address the multiple challenges faced by the developing nations today. Meaningful engagement of stakeholders, national and regional, is probably the most critical aspect requiring attention. Multidisciplinary and multifunctional entities can interact and contribute, to synergise their efforts seamlessly towards a broader goal.

In conclusion, marine eco-concern and more specifically the management of acoustic habitat degradation, can usefully encourage cooperation and joint efforts to enhance our acoustic capacity and our ability to build an effective global UDA framework. To maintain the value of the oceans, our global commons, massive efforts are needed on a regional as well as a global scale, and we need to overcome the fragmentation among the stakeholders. The post-Covid-19 global order will do well to recognise the efficacy of the UDA framework in the IOR and beyond, in helping to achieve safe, secure, sustainable growth for all.

Dr Cdr Arnab Das is the founder and director of the Maritime Research Centre (MRC), Pune, The MRC welcomes innovative ideas that can contribute to the UDA framework. Please email Dr Das at‑: Note: Included above is content from © 2019 Das A: Acoustic Habitat Degradation Due to Shipping in the Indian Ocean Region, Changing Ecosystems and Their Services, published under CC-BY-3.0 license. Available from:’.