 If you went for an evening walk in the bush around Canberra 100 years ago, what would you have seen? The woodlands would have been teeming with wildlife, small animals such as bandicoots, quolls, and bettongs. But since European settlement, the woodlands have been cleared, overgrazed, and overrun by weeds and feral animals, and many of our native species have disappeared. In fact, Australia has the highest mammal extinction rate in the world, and many of these species were lost before we really understood the important roles they play in our ecosystem. So what would happen if we could bring them back? This is the eastern bettong, a rapid-sized relative of the kangaroo. It was once so common in eastern Australia that it was considered a pest, but they disappeared from the mainland around 100 years ago. Luckily, the eastern bettong still survives in Tasmania, and six years ago, we were able to bring a small population and release them into a fenced reserve called Mulligan's Flat Woodland Sanctuary. This sanctuary acts like a giant outdoor laboratory, allowing us to study the impact of the bettong on its environment. Well, since the reintroduction, our bettongs have been getting busy, and not just in the way you might think. They've been digging away every night in search of truffles, roots, and bulbs. I've estimated that each individual bettong can dig up to 200 pits every night. That adds up to three tons of soil turned over every year. As a plant ecologist, I wanted to know how this digging would affect the soils and the vegetation. By measuring and monitoring soil nutrients, temperature and moisture in the diggings, and counting and identifying thousands of tiny seedlings, my research has shown that bettong diggings act like little flower pots, providing the perfect conditions for seeds to germinate. But it's not quite that simple. Reintroducing a species after 100 years can have some unexpected consequences, and the disturbance created by the bettongs could just lead to increased weed invasion. But my research has shown that native plant species actually benefit more from the digging than the weeds. Digging animals like the bettong alter the structure of the ecosystem and provide habitat and resources for other species. And for this reason, they are now known as ecosystem engineers. If we can bring back the bettong, then we could not only save this one species, but also help to restore an entire ecosystem, so that maybe 100 years from now, you can walk through a more diverse and resilient woodland that grew in soils turned over by the bettong. Thank you.