Can turbid coastal environments provide a refuge for coral reefs in periods of warm climate?
Coral reefs are the most highly valued marine ecosystems in the world. However, they are also among the most severely threatened ecosystems by a combination of global threats related to anthropogenic CO2 emissions, as well as more local impacts, including, but not limited to, pollution and overexploitation. At the same time, these reefs are also the most diverse ecosystems in the world, hosting a wealth of species many of which have not been discovered yet. The Coral Triangle, roughly spanning Indonesia, Malaysia, the Philippines and Papua New Guinea, has the most diverse marine ecosystems on Earth, a global biodiversity hotspot. However, they are in close proximity to areas with high human population densities, often depending on the reefs for sustenance. Will these reefs stand a chance in the future with ongoing climate change and pollution?
In 4D-REEF we explore the role of turbid reef habitats in preserving future coral reefs. Analyses of fossil data show that reefs living in so-called turbid habitats, characterized by the influence of terrestrial runoff, played an important role in the origins and maintenance of the coral reefs in the Coral Triangle over the past 25 million years. Usually these reefs are considered as occurring in marginal conditions, but we think that they might have a role in preserving future coral reefs. High coral cover and recruitment on present-day reefs suggests that, despite the presence of large human populations, turbid reefs have the capacity to withstand environmental pressures. In combination with future projections of environmental conditions, we use information of past and present states of reef ecosystems to forecast future trajectories of turbid reef habitats, biota and ecosystem function.
Why is it important for society?
Corals are important for coastal communities for economical revenue, wave and coastal flood protection and biodiversity. The latter is also crucial for food variability, a stable ecosystem, and recreational benefits. Without the coral reef or under decaying reef conditions, the coastal communities could lose the natural barrier from the waves possibly resulting in a destroyed coast, severe damages to nearshore housing and salty water floods that ruin agricultural land and contaminate drinking water sources. Understanding the optimal conditions for coral reef development is important for designing management actions to protect the coral reefs.
What are the overall objectives?
In 4D-REEF we integrate examples from the greenhouse Pliocene, the pre-human Holocene, and the recent to feed into models to predict the future of coral reefs. The Pliocene was the most recent period with a concentration of greenhouse gases comparable to current levels. Investigating Pliocene reefs will provide insight into how greenhouse reefs functioned, their species composition and their distribution. Early Holocene reefs are exposed to minimal human influence, and will be used to assess the biodiversity and ecosystem functioning of pristine reefs. These results will be compared to data from modern reefs.
1. What was the biodiversity of turbid reefs in the past and in what habitats did the reefs grow in past warmer periods of the Earth’s history, and how does this compare to the present?
2. What are the environmental constraints on ecosystem functions of turbid reefs?
3. How can we use information from past reefs to better understand the future trajectories of modern coral reefs, and apply this towards reef restoration actions?
