What Are Connector Species?

Connector species are animals that move energy, nutrients, or materials between ecosystems. On islands—where biodiversity is concentrated and ecological processes are tightly coupled—connector species are often the engines that keep everything running. 

Seabirds are already recognized globally as major land–sea connectors, transporting ocean nutrients to islands and boosting productivity on land and in surrounding waters. 

Marine iguanas and other keystone fauna in the Galápagos act as ecosystem engineers that shape vegetation, nutrient cycling, and landscape structure.  

Crabs, including detritivorous species (an organism that obtains its nutrients by feeding on detritus—decomposing plant and animal parts, as well as feces), play roles in decomposition and nutrient redistribution in marine food webs.  

These are just three examples of connector species; any creatures that participate meaningfully in more than one ecosystem can play these roles. The remarkable diversity of methods by which nutrients can move between land and sea is evidence of the resilience that makes islands so special!

Blue-footed Boobies: Nitrogen Movers & Ocean–Island Connectors

Blue-Footed Boobies are well-known for their colorful feet, silly expressions, and dance moves, but they’re just one of many different species of Boobies that can be found at sea all around the world. All boobies, like other seabirds, are classic connector species because they feed at sea and deposit nutrients on land. 

• They plunge-dive for fish in nutrient-rich waters.  
• Their guano delivers marine-derived nitrogen and phosphorus to island soils—a process called the circular seabird economy.  
• These nutrients leach back into coastal waters, boosting coral growth and fish biomass.  

Blue-footed Boobies nest directly on the ground, which makes them vulnerable to invasive species and predators. Helping restore healthy colonies of seabirds is one of the most effective ways to repair links in the food web, making sure that the circular seabird economy is enriching land and sea together.

Coconut Crabs: The Island’s “Ecosystem Engineers”

Coconut Crabs are giant, charismatic crabs that can grow up to 9 pounds, making them the world’s largest terrestrial arthropod. Their physical size is proportionate to the weight they pull in the places where they live: they’re ecosystem engineers. Their digging, scavenging, and nutrient redistribution reshape soils, influence plant communities, and accelerate decomposition.

• Their burrowing aerates soil and influences plant regeneration.
• Their scavenging moves nutrients across the landscape.
• As large detritivores, they help recycle organic matter back into the ecosystem.

This makes Coconut Crabs key players in maintaining healthy island forests and nutrient-rich soils. When soils are well-aerated, plant roots are able to penetrate more deeply, helping prevent erosion. By recycling and processing organic matter, Coconut Crabs and other detritivores increase the amount of bioavailable nutrients for these plants to flourish.

Galápagos Marine Iguanas: Earth’s Only Sea-Grazing Lizard

Marine Iguanas are endemic to the Galápagos islands, meaning they can be found nowhere else on Earth. That’s not the only thing that makes them special; they live like no other lizard, diving into the ocean and grazing on algae. Because these plants are primary producers–meaning they make energy directly out of inorganic materials, such as sunlight–the Marine Iguanas’ grazing directly connects marine primary production to terrestrial nutrient cycles. 

• They are the only lizards that forage on marine algae, making them primary consumers in the Galápagos marine food web.  
• Their grazing shapes algal communities and prevents algae from becoming overgrown, making room for other organisms on the rocks.
• The nutrients they digest from the algae end up on land, where they contribute to coastal ecosystem health.  

Like the Blue-Footed Boobies, Marine Iguanas literally embody the land–sea connection. The whole land-sea food web depends on them, and their population dynamics are key indicators for the broader impacts of climate change and weather events in the Galápagos.

Why These Three Species Matter for Island Conservation

Together, Coconut Crabs, Blue-Footed Boobies, and Marine Iguanas are three examples that demonstrate the incredible variety of roles that connector species can play. Although they are all keystone species, the term “connector species” may be more useful to describe them, since it illustrates exactly what they do: weave the nutrients of two ecosystems together. 

Here at Island Conservation, we’ve found that islands with healthy populations of connector species such as seabirds have more bioavailable nitrogen and are healthier overall than places where the populations aren’t so strong. This bears out in the near-shore ecosystems, where coral is healthier and fish biomass is greater. It’s the logic behind one of the most cost-effective nature-based environmental solutions in the world: 

Protecting connector species protects entire ecosystems. 

Because they move nutrients, shape habitats, and link land and sea, these species enable the ecological processes that keep islands resilient—from coral reef recovery to forest regeneration to fish productivity. 

This is why restoring island ecosystems is one of the fastest, most measurable ways to strengthen biodiversity and climate resilience. Sign up for our newsletter to learn more about the fascinating island species we’re working to protect!