Bertarelli Summer2024 FINAL - Flipbook - Page 41
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Collaborating recently with scientists who study geomorphology, such
as changes in the sizes of islands, Graham put the seabird/no-seabird
hypothesis to the test again. The size of the islands is controlled by the
balance of sand erosion and accretion of sand. Parrotfish produce a lot of
the sand-grade sediment that builds tropical beaches, and Graham’s earlier
work showed that parrot fish do so three to four times faster on seabird
islands as on ratty islands. While this work is still preliminary, Graham says,
“Seabird-rich islands are really sort of self-sustaining.” It’s possible that the
growth of these seabird-rich islands could help keep pace with sea-level rise
caused by climate change.
All of which leads to an obvious conclusion: The rats have got to go. And,
in fact, Graham says momentum around eradicating rats and other predators to restore islands and their seabird populations is growing. Around a
thousand islands have had invasive or predatory mammals removed.
Graham’s work continues to expand both geographically and conceptually. In the Aldabra Atoll, Graham and Seychelloise doctoral student
Jennifer Appoo have documented seabirds’ influence on nutrient cycling
through mangroves and into populations of snails and crabs. The nutrients
are then exported up the food web to the large populations of fish and
sharks in the region. In Tetiaroa Atoll in French Polynesia, Graham and his
colleagues are looking at the cycling of elements like zinc and iron, testing
whether seabirds increase the concentrations of these important micronutrients available to people through the fish they catch and eat.
“There’s multiple lines of evidence that we’re building up,” says Graham
summarizing years of research, “that the productivity and the biomass and
ecosystem processes are really supercharged next to the seabirds.” And
understanding just what supercharges a reef helps build a future where
coral still flourish.
reproduction work and Nick
Graham’s ecosystem-scale research comes at a critical moment for corals.
Already, half the world’s corals have been lost to warming waters since the
1970s. Yet coral reefs are foundational to the marine systems, providing
habitat for nearly 900,000 other species, including serving as nurseries for
enormous quantities of fish people eat. So much so that 1 billion people
depend on reefs for their primary source of protein. Coral reefs are also
critical for protecting tropical coastlines. They provide essential defense
against ever more intense storms, diverting 97 percent of a storm’s energy
from reaching the shore. Understanding the full range of the corals’ story:
from untangling the keys to coral reproduction to the powerful effects of
seabirds on ecosystem health buy valuable time for the reefs. And there
really isn’t any to waste.
BOTH JAMIE CRAGGS9 AQUARIUM-BASED
Juli BErwald is a science writer and author of Spineless: The Science of Jellyfish and the
Art of Growing a Backbone and Life on the Rocks: Building a Future for Coral Reefs. More
about her writing can be found at juliberwald.com.
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