Long-term dynamics of hard coral cover across Indonesia

Most comparative studies assessing reef health focus on living hard coral cover as the key metric. In Indonesia, in situ monitoring of coral cover has been ongoing for over five decades. However, as monitoring data and research findings are predominantly published in the local language (Bahasa Indonesia), local data often escape global attention, resulting in Indonesian coral reefs receiving less scientific attention despite accounting for ~ 15% of all coral reef area globally. Here, we systematically compiled both globally and locally published data on coral cover across Indonesia to assess changes over recent decades. We analysed 7,614 data entries extracted from 621 publications and found that the majority (79.1%) of the publications were written in Bahasa Indonesia, constituting 63.4% of the total data entries. Our dataset revealed limited evidence of net declines in coral cover over the last three decades (1994–2022). There was also no clear relationship between coral cover and human density, as well as with the thirteen environmental/anthropogenic drivers examined. We discuss several factors that may contribute to this lack of detectable large-scale change including: recent data potentially representing a ‘shifted baseline’; the ‘averaging out’ of localised changes in coral cover dynamics at a broad scale; sampling biases; and/or the potential resilience of Indonesian coral reefs compared to other regions. This study highlights the wealth of accessible local coral reef data published in languages other than English and emphasises the importance of using such data to enhance our understanding of the long-term dynamics of coral reef ecosystems worldwide.