Grassroots Vol 21 No 3 | Page 30

NEWS

According to the findings of Brom ’ s recently completed PhD research thesis , delaying mowing until the end of November promotes a follow-on population from the seed stock .
To understand how she came to this conclusion , a brief explanation of her research paper topic is required .
Brom shares she was interested in how wild pollinators were responding to urban land-use patterns across a number of environmental gradients in the Cape context .
“ Internationally , we know that some guilds of pollinators , particularly largerbodied insects and cavity nesters , are thriving in cities because they are able to exploit the resources provided by gardeners .”
For her research purposes , Brom focused on monkey beetles . In 2018 and 2019 , she surveyed them and the flower communities present in vacant lots and city parks , as well as some natural areas and farms for comparative purposes .
“ Over those two years , I visited 142 locations from almost all parts of the city during spring , which is when the beetles are active in their adult phase .”
Because she was documenting flowers , Brom noticed in 2018 that while contractors were sometimes mowing around the indigenous bulbs and daisies growing on road verges while they were in flower , they would return as soon as the plants stopped flowering . In other words , before the seeds would have had a chance to mature .
“ This meant that there would be no follow-on population from the seed stock . For bulbs , the flowers return for a few more years ; for the rapidly reseeding daisies , it often means that the patch is completely lost .”
In 2019 and 2020 , Brom set up observation plots in nine parks : five in the northern suburbs and four in the southern suburbs .
She monitored the phenology ( observable phases of a life cycle ) of the flowers from bud to seed-broadcast ( mature seed ) to determine how long to wait for the flowers to complete their reproductive cycle .
“ The answer was that the main season concluded in mid-November , and the City has taken this on board . This year ’ s no-mow signage for designated parks says ‘ flowering and seeding ’. That ’ s a big win for urban biodiversity .”
Bug in the system
Her research also focused on the symbiotic relationship that exists between pollinators and plants .
Brom explains that pollination is a service provided to plants by many different species of animals , including bees , butterflies , flies , mosquitoes , beetles , birds , bats and even mice .
“ These animals and plants have coevolved to be matched to each other ’ s preferences and needs . For example , monkey beetles are important for flowers in the vygie , daisy and iris families .”
However , not all pollinators have the ability to travel long distances between patches of vegetation . Brom says more mobile organisms , such as wetland birds , need patches at less regular intervals .
“ Honeybees can fly about 5 km to find a good stand of Eucalyptus , but monkey beetles and sweat bees ( Halictids ) need patches of flowers more regularly throughout the landscape . This is where road verges , residential gardens and parks come in .”
She says they form stepping stones – patches of suitable habitat between which organisms can move – which are crucial to the future existence of certain insect species .
“ Overall , insect biomass is in decline . And the losses counted as threatened species pale in comparison to the overall loss in biomass happening in the background , even for species that are currently considered ‘ least concern ’.
A group of scientists in Germany measured it . Germany lost 75 % of its insect biomass over 30 years ,” she says .
Brom says there are cascading effects of this ; everything that eats insects , everything that the insects pollinate , is affected .
“ Scientists are warning us that we are heading for the sixth mass extinction event – a fact that in my mind is as serious as climate change , if not more so .”
But , she has a message of hope .
Brom says because cities have been overlooked as an opportunity to be managed with nature in mind , there are lots of easy things that can be done to improve the ecological functioning of natural and green spaces .
Changing mowing schedules to allow indigenous wildflowers to flourish is one . Another is through the decisions made in home gardens .
“ Knowing the historical vegetation type of your area and planting locally indigenous is the first step . Fynbos Life Nursery , Veld and Sea , Goodhope Nursery , are excellent resources to help you navigate planting decisions .”
For Brom , one of the biggest takeaways from her research is that urban landscapes are an under-researched opportunity for the management of biodiversity .
“ But it can only be achieved in partnership with the public and if there is general buy-in from the affected neighbours ,” she concludes .
Follow Peta Brom on Instagram @ doorstepecology .

Congress 56 Sponsors

29 Grassroots Vol 21 No 3 November 2021