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Why it’s time to reconsider the ecological contribution of introduced species – even in New Zealand

<p>The loss of biodiversity is one of the most catastrophic developments of our time. The impacts will possibly <a href="https://www.nature.com/articles/461472a">outpace those of global warming</a>.</p> <p><img src="https://images.theconversation.com/files/433029/original/file-20211122-15-tb7265.jpg?ixlib=rb-1.1.0&amp;q=45&amp;auto=format&amp;w=237&amp;fit=clip" alt="A fantail" /></p> <p><span class="caption">New Zealand’s pīwakawaka: conservation often focuses on saving native species.</span> <span class="attribution"><span class="source">Shutterstock/Imogen Warren</span></span></p> <p>Growing evidence that humans have triggered a <a href="https://www.pnas.org/content/117/24/13596">sixth global mass extinction</a> means the protection of remaining species is a <a href="https://sdgs.un.org/goals">priority beyond dispute</a> to secure ecological services such carbon cycling, clean water and air, and healthy oceans.</p> <p>The key drivers of species loss are climate change, habitat degradation, <a href="https://www.nature.com/articles/nature11148?report=reader">pollution</a>, and <a href="https://link.springer.com/article/10.1007/s10531-018-1595-x">exotic species that become invasive</a>. This has led conservation ecologists to follow the simple rule of “protect natives, fight exotics”.</p> <p>If we had an unlimited budget, I would hardly challenge this view. But in a world where natural ecosystems face many other global changes apart from species loss, I argue we should reconsider the <a href="https://www.frontiersin.org/articles/10.3389/fpls.2021.758413/full">ecological role exotic species play</a>.</p> <h2>Ecosystem function over species mix</h2> <p>One could argue ecosystems are inherently so complex that we can never appreciate the exact contribution of an individual species, and therefore native species need to be protected at all cost.</p> <p>But this argument can be turned around. In many cases, exotic species are not detrimental to the resident species communities. It is not until an exotic species becomes invasive that <a href="https://rewilding.org/wp-content/uploads/2012/04/IUCN-GISP.pdf">substantial harm happens</a>.</p> <p>The deliberate spread of species has been an integral part of human evolution for thousands of years. Many economically important plant species are exotics in most places, but they make it possible to feed our growing population.</p> <p><img src="https://images.theconversation.com/files/433030/original/file-20211122-25-khff1x.jpg?ixlib=rb-1.1.0&amp;q=45&amp;auto=format&amp;w=237&amp;fit=clip" alt="New world cacti and succulents in Greece." /></p> <p><span class="caption">New worlld cacti and succulents have become part of the Mediterranean landscape.</span> <span class="attribution"><span class="source">Shutterstock/Anna Holyph</span></span></p> <p>In a physically highly connected world, unintentional relocation of both terrestrial and marine species has now also become unavoidable.</p> <p>In some cases, introduced species can even complement native ecosystems. New world succulents are now very much part of the Mediterranean landscape, without <a href="https://www.presentica.com/doc/11177197/the-role-of-new-world-biodiversity-in-the-transformation-of-document">harming the local flora</a>.</p> <p>Sometimes, introduced species perform ecological functions similar to those that are (or were) performed by natives. For instance, European gorse stabilises coastal slopes in New Zealand, providing a <a href="https://pubmed.ncbi.nlm.nih.gov/19644109">nursery for local plants</a>.</p> <p><img src="https://images.theconversation.com/files/433003/original/file-20211121-27-ccesaa.jpg?ixlib=rb-1.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" alt="Gorse covering a hill in New Zealand." /> <span class="caption">Gorse can act as a nursery plant for New Zealand’s native plant species.</span> <span class="attribution"><span class="source">Shutterstock/Filip Fuxa</span></span></p> <p>In one particularly spectacular case, extinct tortoises were intentionally replaced with an exotic species through “assisted colonisation”. It seems to have <a href="https://pubmed.ncbi.nlm.nih.gov/23773124/">worked</a>.</p> <p>However, earlier and much less scientifically informed attempts of assisted colonisation, such as the deliberate introduction of cane toads in Australia’s tropical north-east, <a href="https://zslpublications.onlinelibrary.wiley.com/doi/abs/10.1111/j.1469-1795.2009.00319.x">went terribly wrong</a>.</p> <h2>The bias of human perception</h2> <p>There are many ecosystem services humanity depends on: clean water, carbon cycling, removal of pollutants and excessive nutrient loads, mitigation of global warming through land-based and marine carbon sequestration, erosion prevention, just to name a few.</p> <p>The preservation of native species is one way of ensuring those services for future generations. An approach focused on ecological function weighs the cost of protecting natives and combating exotics against the role of new species assemblages shaped by human interference.</p> <p>At approximately equal cost, should the addition of a breeding pair of a rare bird be prioritised over the reforestation of several hectares of land? Such decisions are often difficult and must be based on the available science.</p> <p>Clearly, there may be other reasons — cultural or aesthetic values for example — to protect native species, beyond the provisioning of ecosystem services. But people seem biased by what they are used to.</p> <p>For example, Switzerland provides <a href="https://www.bbc.com/news/world-europe-42731932">generous subsidies</a> to farmers for maintaining picturesque alpine meadows, even though the native vegetation before human intervention was a much less biologically diverse alpine forest.</p> <p>In Central Europe, the recently introduced Tree of Heaven (<em>Ailanthus altissima</em>) triggered substantial efforts to eradicate it, while the European chestnut (<em>Castanea sativa</em>), introduced by the Greeks and Romans some 2000 years ago, is highly valued and enjoys <a href="https://link.springer.com/article/10.1007/s00334-004-0038-7">protection and even reforestation programmes</a>.</p> <p>The above examples illustrate why we may need a more sober approach centred on ecological function to effectively protect our remaining natural treasures and the ecosystem services they provide.</p> <p>The <a href="https://www.frontiersin.org/articles/10.3389/fevo.2021.711556/abstract">milestones in the evolution of life</a> did not depend on individual species or species assemblages, but on the emergence of new functional traits such as photosynthesis, predation or flight. Similarly, humankind ultimately relies on functioning ecosystems, regardless of which species provide them.<!-- Below is The Conversation's page counter tag. Please DO NOT REMOVE. --><img style="border: none !important; box-shadow: none !important; margin: 0 !important; max-height: 1px !important; max-width: 1px !important; min-height: 1px !important; min-width: 1px !important; opacity: 0 !important; outline: none !important; padding: 0 !important; text-shadow: none !important;" src="https://counter.theconversation.com/content/171195/count.gif?distributor=republish-lightbox-basic" alt="The Conversation" width="1" height="1" /><!-- End of code. If you don't see any code above, please get new code from the Advanced tab after you click the republish button. The page counter does not collect any personal data. More info: https://theconversation.com/republishing-guidelines --></p> <p><span><a href="https://theconversation.com/profiles/sebastian-leuzinger-797584">Sebastian Leuzinger</a>, Professor, <em><a href="https://theconversation.com/institutions/auckland-university-of-technology-1137">Auckland University of Technology</a></em></span></p> <p>This article is republished from <a href="https://theconversation.com">The Conversation</a> under a Creative Commons license. Read the <a href="https://theconversation.com/why-its-time-to-reconsider-the-ecological-contribution-of-introduced-species-even-in-new-zealand-171195">original article</a>.</p> <p><em>Image: Shuttershock</em></p>

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Home gardens vital for pollinators

<h2><strong style="font-size: 14px;">They provide a rich and diverse nectar source, study finds.</strong></h2> <div class="copy"> <p>Urban areas are a surprisingly rich food reservoir for pollinating insects such as bees and wasps, according to a UK study <a rel="noreferrer noopener" href="https://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2745.13598" target="_blank">published</a> in the <em>Journal of Ecology</em>.</p> <p>Home gardens are particularly important, the study found, accounting for 85% of the nectar – sugar-rich liquid that provides pollinators with energy – within towns and cities and the most diverse supply overall.</p> <p>Results showed that just three gardens generated on average around a teaspoon of the liquid gold – enough to attract and fuel thousands of pollinators.</p> <p>“This means that towns and cities could be hotspots of diversity of food – important for feeding many different types of pollinators and giving them a balanced diet,” says lead author Nicholas Tew, from the University of Bristol.</p> <p>“The actions of individual gardeners are crucial,” he adds. “Garden nectar provides the vast majority of all. This gives everyone a chance to help pollinator conservation on their doorstep.”</p> <p><a rel="noreferrer noopener" href="https://www.pollinator.org/pollination" target="_blank">Pollinators</a> include bees, wasps, butterflies, moths, bats and beetles. They are critical for ecosystems and agriculture as most plant species need them to reproduce, and <a rel="noreferrer noopener" href="https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.453.4134&amp;rep=rep1&amp;type=pdf" target="_blank">research suggests</a> their survival relies especially on the diversity of flowering plants.</p> <p>To explore how our sprawling urban areas could support them, Tew’s research group previously led the <a rel="noreferrer noopener" href="http://www.bristol.ac.uk/biology/research/ecological/community/pollinators/" target="_blank">Urban Pollinators Project</a> in collaboration with other universities. They found that cities and gardens – community and private – are vital for pollinators, leading them to question how to quantify and harness this resource.</p> <p>“The gap in our knowledge was how much nectar and pollen urban areas produce and how this compares with the countryside,” Tew explains, “important information if we want to understand how important our towns and cities can be for pollinator conservation and how best to manage them.”</p> <p>So, for the current study, Tew and colleagues measured the supply of nectar in urban areas, farmland and nature reserve landscapes, and then within four towns and cities (Bristol, Edinburgh, Leeds and Reading) to determine how much nectar different land uses produce.</p> <p>To do this, they extracted nectar from more than 3000 flowers comprising nearly 200 plant species using a fine glass tube and quantified it using a refractometer, an instrument that measures how much light refracts when passing through a solution.</p> <p>Then they sourced nectar measurements from other published studies and combined the nectar-per-flower values with numbers of flowers from each species in different habitats as previously measured by the group.</p> <p>Overall, nectar quantity per unit area was similar in urban, farmland and nature reserve landscapes. But urban nectar supply was most diverse, as it was produced by more flowering plant species. And while private gardens supplied similarly large amounts per unit as allotments, they covered more land – nearly a third of towns and cities.</p> <p>It’s important to note the findings are specific to the UK, and maybe parts of western Europe, Tew says. Most urban nectar comes from ornamental species that are not native, which can be attractive to generalist pollinators but may not benefit specialist species that feed from selective native flower species.</p> <p>Thus private gardens in other regions might have different benefits. Australia, for instance, has more endemic species and specialist pollinators than the UK, so while non-natives would still provide some benefit, natives may be more important overall.</p> <p>Most recommendations for attracting pollinators in Australia include supporting native bees and other local specialists. Suggestions include planting more native species and providing <a rel="noreferrer noopener" href="http://www.australianenvironmentaleducation.com.au/australian-animals/australian-pollinator-week/" target="_blank">accommodation</a> for native bees, most of which are solitary species – unlike the familiar, colonial European honeybee.</p> <p>But in general, Tew says home gardeners can all support biodiversity with some key strategies, especially planting as many nectar-rich flowering plants as possible and different species that ensure flowers all year round.</p> <p>Other <a rel="noreferrer noopener" href="https://www.rhs.org.uk/science/conservation-biodiversity/wildlife/plants-for-pollinators" target="_blank">recommendations</a> include mowing the lawn less often to let dandelions, clovers and other plants flower, avoiding <a rel="noreferrer noopener" href="https://cosmosmagazine.com/biology/scientists-call-for-urgent-action-on-bee-killing-insecticides/" target="_blank">pesticides</a> and never spraying open flowers, and covering as much garden area as possible in flowery borders and natural lawns.</p> <!-- Start of tracking content syndication. Please do not remove this section as it allows us to keep track of republished articles --> <img id="cosmos-post-tracker" style="opacity: 0; height: 1px!important; width: 1px!important; border: 0!important; position: absolute!important; z-index: -1!important;" src="https://syndication.cosmosmagazine.com/?id=138747&amp;title=Home+gardens+vital+for+pollinators" alt="" width="1" height="1" /> <!-- End of tracking content syndication --></div> <div id="contributors"> <p><a href="https://cosmosmagazine.com/science/biology/home-gardens-vital-for-pollinators/">This article</a> was originally published on <a href="https://cosmosmagazine.com">Cosmos Magazine</a> and was written by <a href="https://cosmosmagazine.com/contributor/natalie-parletta">Natalie Parletta</a>. Natalie Parletta is a freelance science writer based in Adelaide and an adjunct senior research fellow with the University of South Australia.</p> <p><em>Image: Cosmos Magazine</em></p> </div>

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