Disclaimer before we begin: The image accompanying this article is NOT a monarch butterfly. We all know what they look like, and yes, they're beautiful...but I wanted to highlight some of the overlooked beauty we have locally, with a photo i took of a wee little (but incredibly vibrant) native moth.

Over the past few months, Nannup has been alive with a striking visitor...monarch butterflies in numbers rarely seen before. Their presence has become a talking point across the community, even finding its way into news stories after the recent Nannup Flower & Garden Festival exposed them to the thousands of visitors. For many, it feels like a small miracle: bold flashes of vibrant orange drifting through the streets.

But as with many things in ecology, the full story is a little more complex.

What’s really happening ecologically?

Monarchs (Danaus plexippus) are mesmerising. But when a non‑native species turns up in big numbers, it’s worth asking: what energy are they tapping, where does it go, and what shifts follow in the wider web of life? Below are the key knock‑on effects I see locally.

1) The “energy bottleneck” problem

In healthy native food webs, energy flows from plants → herbivores → predators, with many pathways. Moths and butterflies play an incredibly important and often overlooked role in this transfer of energy. Monarch caterpillars feed almost exclusively on non‑native milkweeds (Gomphocarpus/Asclepias spp.). They sequester cardiac glycosides (cardenolides) from those plants, which makes them distasteful or toxic to many vertebrate predators.

• Result: a lot of plant energy is converted into defended monarch biomass that many native predators won’t (or can’t) use. That’s an energetic dead‑end as opposed to a native caterpillar that would feed native birds, reptiles, and insects.
• It’s not absolute though...some predators (e.g., certain wasps, mantises, spiders) will still take monarch larvae, but compared with native prey, the transfer up the food chain is poorer and patchier. That’s the bottleneck.

2) Predator subsidies (the flip side)

Abundant, conspicuous caterpillars can subsidise the few predator populations that do eat them, especially paper wasps (including invasive species) and generalist arthropod predators.

• Why this matters: when wasps boom on an easy food source, they don’t stop at monarchs; they increase pressure on native caterpillars and other invertebrates too. That can amplify impacts well beyond the initial novelty species.

3) Weeds and landscape spillover

The real driver of Monarch abundance here is the widespread invasion of narrow-leaf cottonbush (Gomphocarpus fruticosus) across timber plantations, road reserves, and natural areas.

Cottonbush is a declared pest in Western Australia and forms dense infestations that displace native vegetation, alter fire regimes, and create long-lasting seed banks that are expensive and difficult to control.

As it spreads through the landscape, it provides an almost unlimited food source for Monarch caterpillars. This artificially boosts their numbers well beyond what the local ecology can balance. Unlike in their home range, where natural enemies regulate populations, here they become another imbalance layered on top of the ecological disruption caused by the weed itself.

What we end up with is a double impact:

• Cottonbush invasion degrading native habitats.
• Monarch proliferation tying up energy in a species out of step with the local food web.

Normalising Monarchs as a spectacle overlooks the fact that their presence here is inseparable from the damage caused by cottonbush in our natural areas.

4) Nectar competition and ecological displacement

Adult monarchs are generalist, high-throughput nectar feeders. When they occur in unusually large numbers, they can pre-empt nectar on popular blooms during the same peak foraging windows used by native pollinators.

What that means in practice:

• Exploitative competition: monarchs remove nectar before native bees, wasps, flies and butterflies arrive, forcing those natives to switch to lower-reward flowers or spend more time searching.
• Crowding effects: on dense floral displays, sheer abundance can reduce access for smaller native insects, changing who visits which plants and when.
• Flow-on risks for natives: if visitation patterns shift away from certain native plants at key times, some species may receive fewer or less effective pollinator visits, which can subtly affect seed set and plant recruitment.

The concern here is about resource pressure. In boom years, a large, non-native nectar forager can tilt local pollination networks, not by being a superior pollinator, but by soaking up nectar and space that native insects would otherwise use. The scale of impact will vary with season, floral abundance, and site, but the mechanism is straightforward and consistent with how nectar competition plays out whenever a single forager becomes disproportionately abundant.

5) Aesthetics vs ecology

They’re beautiful, no argument. But beauty can mask harm. Building tourism narratives around an attractive non‑native can send the signal: “plant more of the thing that feeds it,” even when that thing is a weed. Imagine promoting arum lily in Busselton or blackberry in Pemberton because they look nice or produce delicious fruit...good optics, poor ecology.

6) From monarchs to mindsets: “holistic” isn’t always holistic

The monarch story also shines a light on a bigger challenge: how we think about our gardens and landscapes.

Plenty of garden philosophies call themselves holistic while optimising a closed, human-designed system, thinking holistically about their system and perhaps a few external inputs, but without asking how that garden/system fits into the wider ecology. Monarchs thrive here precisely because cottonbush and other exotics have been allowed to dominate parts of the landscape. When we celebrate that outcome, we’re confusing surface level aesthetics for true ecological health.

7) Fair balance: are there any positives here?

• Engagement: Monarchs get people looking. That curiosity can be redirected toward our own pollinators and plants.
• Learning moment: This is a chance to talk deeper about ecological food webs and why natives matter, with local examples.

A better, local alternative for Nannup

We don’t need to lean on introduced species for wonder. Our native bees, hoverflies, wasps, moths, and butterflies are extraordinary, and they belong here.

Here's an idea worthy of consideration for future festivals:

Native Pollinator Bingo
Hand out bingo cards featuring native pollinators likely in town that month. Bees, flies, wasps, butterflies, moths. Invite people to photograph and tick them off as they move around town, share sightings, and learn simple ID traits.

Lets re‑anchor joy in the species and systems that make this region unique...Let's truly value our local ecology!