Fixing our Bug Problem
By: Wwf Hk
Tags: Biodiversity, Nature, Extinction, Insects, Environment

by Thomas Gomersall

Insects may not be what many would consider endangered species, but according to a devastating 2019 study in Biological Conservation, 41 per cent are in decline. An additional third are threatened and without immediate, radical action, most could be extinct within decades in what many have dubbed the ‘Insect Apocalypse’ (Sánchez-Bayo & Wyckhuys, 2019). This wouldn’t just be apocalyptic for insects, but for the countless animals and plants that they feed and pollinate, including our food crops. Yet in places such as Hong Kong, people continue to destroy their habitats for development and use pesticides that kill far more insects than the mosquitos they are intended for (Williams, 2019).

But if Swedish teen environmental activist Greta Thunberg proves anything, it’s that ordinary citizens can make a difference. Here are some ways Hongkongers can help protect local insects.

Citizen scientist programmes, such as City Nature Challenge, help familiarise people about insects. Photo credit: WWF-Hong Kong

Love the Bugs

Public support is integral for successful conservation. But widespread public ignorance of the importance of insects and limited exposure to them make insect conservation a tough sell (Tsang, 2019).

Better education programmes about insects for schools and the wider public can help address this, while citizen scientist programmes, such as City Nature Challenge, help familiarise people about insects.

“If you want to ask people to conserve insects, the most direct way is through [using] photography to make them realise that they can look very beautiful” says Toby Tsang, a post-doctoral urban ecology researcher at the University of Hong Kong. “If you can manage to somehow first promote [insect conservation] through photography, I think more people will start paying attention.”

Tropical and subtropical insects can only survive within a narrow temperature range. Photo credit: Thomas Gomersall

Tackle Climate Crisis

This is a particularly important measure for protecting Hong Kong insects, as tropical and subtropical insects can only survive within a narrow range of temperatures, making it especially hard for them to cope with rapid warming (Bonebrake & Mastrandrea, 2010), as shown by the mass bee die-offs in last summer’s heatwave (Williams, 2019) and the expected significant declines in butterfly diversity in country parks from current warming projections (Cheng & Bonebrake, 2017). Measures to reduce Hong Kong’s carbon footprint include buying more locally sourced foods*, eating less meat and using low-emission public transport** and most importantly, continuing to pressure the government to cut emissions.

Roofs of residential high rises provide plenty of space for communal rooftop gardens. Photo credit: Mathew Pryor

Bug Cities

While natural areas certainly provide better habitat overall, urban green spaces in Hong Kong (e.g. parks) are nonetheless surprisingly valuable for insect conservation. They support considerable insect diversity (including 58 of Hong Kong’s 250 butterfly species) and can help insects to move between the fragmented country parks, maintaining vital inter-population gene flow. However, habitat quality in parks is limited by frequent pesticide spraying and vegetation trimming (Tam & Bonebrake, 2016; Bonebrake, 2019).

Luckily, ordinary citizens can easily create more insect-friendly green spaces themselves. Those with conventional gardens can do this by leaving small sections of them untended. But roofs of residential high rises also provide plenty of space for communal rooftop gardens and getting building management permission to start one is usually fairly easy (Pryor, 2019). If individuals each add their own plants to the garden, this will lead to a greater plant abundance that can support more insect species (Tsang & Bonebrake, 2017), particularly if these include native species such as the Chinese ixora and rhododendrons (Burghardt et al, 2009; Tam & Bonebrake, 2016; Ng & Corlett, 2000).

Seasonally blooming plants, such as Chinese ixora are best for pollinators. Photo credit: Thomas Gomersall

In return, rooftop gardens and the insects they attract (including butterflies, bees and beetles) can bring unexpected benefits for gardeners (Pryor, 2019). For instance, a high abundance and diversity of pollinators have been linked to higher crop yields (Garibaldi et al, 2014), good news for those who like growing fruit and vegetables on the roof. Even the process of creating and tending to a rooftop garden has been found to have great psychological benefits for people.

“I do a lot of research into why people farm on the roof. [Roof gardens] produce huge amounts of happiness.” says Mathew Pryor, Head of the Division of Landscape Architecture at the University of Hong Kong. “Everybody who participates in a rooftop farm is blissfully happy. […] It’s a personal project.”

As for natural insect habitats, Hongkongers should lobby their legislators to do more to protect these areas and vote for those whose environmental policies go towards meeting such goals.

Growing flowers of varying lengths will help butterflies that specialise in feeding from long-bodied flowers. Photo credit: Thomas Gomersall

Food, Glorious Food

When creating insect-friendly green spaces, it’s also important to consider food sources, particularly to encourage butterfly breeding, as the caterpillars of many species will only feed from specific plants (Lo & Hui, 2004, p.64) ***. Seasonally blooming plants, such as Chinese ixora are best for pollinators as they grow quickly and produce lots of flowers and nectar. Growing several species that bloom at different times of the year ensures that pollinators have abundant food year-round (Pryor, 2019) while growing flowers of varying lengths will help butterflies that specialise in feeding from long-bodied flowers along with more generalist feeders (Kunte, 2007). Some butterflies will also feed from fluids produced by rotting fruit such as papaya and banana skins. (Lo & Hui, 2004, p.65; Bunker, 2019).

Pesticides are the second-biggest driver of global insect declines. Photo credit: Thomas Gomersall

Put down the Pesticide

Of course, not everyone who keeps plants may want to attract insects that could potentially strip them to the stem. But don’t reach for that bug-spray. Pesticides are the second-biggest driver of global insect declines (Sánchez-Bayo & Wyckhuys, 2019) and there are plenty of other means to keep insects away from plants without killing them.

Planting marigolds next to other plants is one environmentally friendly way to guard against insect infestation. Photo credit: Thomas Gomersall

One way is the plant-by-plant method, in which bad-smelling plants like marigolds are placed close to other plants to ‘guard’ them from insects. Another is to use non-toxic, homemade sprays like water-diluted vinegar or water boiled with garlic. If the odour generated by this method puts you off as much as the insects, a less smelly though no-less effective or insect-friendly option would be to use Neem oil, which is available in most gardening shops. (Bunker, 2019).

External Links

* Locally sourced food in Hong Kong: https://medium.com/wwfhk-e/eating-sustainably-in-hong-kong-65b7f0dff961

** Advice on cutting personal carbon emissions: https://medium.com/wwfhk-e/when-the-lights-go-back-on-thoughts-on-earth-hour-96e70c5307fc

*** Specific caterpillar food plant preferences of the world’s butterflies and moths: https://www.nhm.ac.uk/our-science/data/hostplants/search/index.dsml

References

· Bonebrake, TC (PhD), interviewed by Thomas Gomersall, 2019, The University of Hong Kong.

· Bonebrake, T.C. and Mastrandrea, M.D. 2010. Tolerance adaptation and precipitation changes complicate latitudinal patterns of climate change impacts. PNAS. 091184107.

· Bunker, S, interviewed by Thomas Gomersall, 2019, World Wide Fund for Nature — Hong Kong.

· Burghardt, K.T., Tallamy, D.W. and W.G. Shriver. 2009. Impacts of native plants on bird and butterfly biodiversity in suburban landscapes. Conservation Biology, vol. 23 (1): 219pp–234pp.

· Cheng, W. and Bonebrake, T.C. 2017. Conservation effectiveness of protected areas for Hong Kong butterflies declines under climate change. Journal of Insect Conservation, vol. 21: 599pp-606pp.

· Garibaldi, L.A., Carvalheiro, L.G., Leonhardt, S.D., Aizen, M.A., Blaauw, B.R., Isaacs, R., Kuhlmann, M., Kleijn, D., Klein, A.M., Kremen, C., Morandin, L., Scheper, J. and R. Winfree. 2014. From research to action: enhancing crop yield through wild pollinators. Frontiers in Ecology and the Environment, vol. 12 (8): 439pp–447pp.

· Lo, P.Y.F. and Hui, W.L. 2004. Hong Kong Butterflies, 1st edn., Friends of the Country Parks, Hong Kong. 64pp–65pp.

· Ng, S.C. and Corlett, R.T. 2000. Comparative reproductive biology of the six species of Rhododendron (Ericaceae) in Hong Kong, South China. Canadian Journal of Botany, vol. 78 (2): 221pp–229pp.

· Pryor, M (PhD), interviewed by Thomas Gomersall, 2019, The University of Hong Kong.

· Sánchez-Bayo, F. and Wyckhuys, K.A.G. 2019. Worldwide declines of the entomofauna: A review of its drivers. Biological Conservation, vol. 232: 8pp–27pp.

· Tam, K.C. and Bonebrake, T.C. 2016. Butterfly diversity, habitat and vegetation usage in Hong Kong urban parks. Urban Ecosystems, vol. 19: 721pp–733pp.

· Tsang, TPN. (PhD), interviewed by Thomas Gomersall, 2019, The University of Hong Kong.

· Tsang, T.P.N. and Bonebrake, T.C. 2017. Contrasting roles of environmental and spatial processes for common and rare urban butterfly species compositions. Landscape Ecology, vol. 32 (1): 47pp–57pp.

· Williams, M., ‘The insect apocalypse is coming: Hong Kong moth study shows the threats and complexities’. South China Morning Post, 31 March 2019, https://www.scmp.com/magazines/post-magazine/long-reads/article/3003821/insect-apocalypse-coming-study-hong-kong-moth (Accessed: 1 April 2019)