50 Years of Rock Records in Western Australia Show Life's Oldest Fossils Are Fragile
A new review in Alcheringa says the state's microbialites, which stretch back almost 3.5 billion years, may signal ecological stress, but fossil sites and living reefs face damage from tourism, collecting and climate change.
Long before forests reached skyward, animals walked on land and dinosaurs rose and fell, Earth was shaped by a much smaller and more unassuming form of life. Its traces survive as microbialites, the earliest visible evidence of life on the planet, and Western Australia holds an extraordinary record of them. A review of 50 years of research on that record, published in the journal Alcheringa, argues that the archive is both scientifically priceless and in danger.
Microbialites are mounded structures that form when communities of microbes either precipitate minerals or trap and bind sediment. Stromatolites, the best known type, have distinctive layers. Thrombolites have a clotted texture instead. Western Australia's examples run from the oldest known, preserved in rocks almost 3.5 billion years old in the Pilbara, to living examples in the UNESCO World Heritage area of Shark Bay. Heidi Jane Allen, writing in The Conversation about the review, said the living sites have been described as a "Rosetta Stone" for understanding their fossil counterparts, because they show the processes that built the ancient rocks.
What the record can say is considerable. It offers clues about where some of the earliest life lived, where scientists might look for life beyond Earth, and how the atmosphere became rich in oxygen, paving the way for more complex life. It also preserves how life responded to upheaval. The state's microbialite record spans at least one, and potentially two, of Earth's five major mass extinctions. Evidence suggests a sudden increase in microbialites often preceded or coincided with major ecological disruption, which hints that they could act as early indicators of ecological stress.
The review also lists what is still unknown. Scientists are still debating how to tell structures built by life from those produced by nonbiological processes. They cannot always say with certainty what environments ancient microbialites formed in, or what controls their shape. They do not fully know how closely modern examples reflect fossil forms. Why thrombolites are clotted rather than layered remains a conundrum, as does how far back they go. Western Australia may hold some of the oldest known thrombolites, but they have not yet been documented in detail.
Despite their rocklike appearance, microbialites are surprisingly fragile. Living ones are highly sensitive to disturbance, and their extremely slow growth means physical damage can take decades or centuries to repair, if it is repaired at all. In May 2024, dozens of aurora chasers trampled 2,000-year-old thrombolites in a restricted area at Lake Clifton. At Lake Clifton and Shark Bay, some events may have already caused irreparable damage. Many modern sites face pressure from changes in water quality, climate change and growing visitor numbers.
Fossil sites are vulnerable too. Across Western Australia, tourism, inappropriate collecting and even scientific sampling can damage irreplaceable outcrops. Protecting them falls under geoheritage, which the authors say remains poorly recognized and under-resourced in Australia at both the federal and state levels. The 2021 Australian State of the Environment report concluded that "the overall outlook for geoheritage is poor" because of a lack of national frameworks, focus and resourcing. According to the authors, little has changed since. Their case is that preserving the evidence, living and fossil, is the only way future scientists can answer questions nobody has yet thought to ask.
