Green metalwing, near Chiang Mai, Thailand.
The last time a major infrastructural project took place close to MacRitchie Reservoir, at least one native species became extinct. Neurobasis chinensis is a damselfly that vanished from Singapore following the construction of the Pan-Island Expressway in 1972, right by a portion of the Upper MacRitchie Basin, some distance from the western tip of the reservoir proper. The roadworks presumably led to the discharge of earth and other debris into a stream near the exit to Eng Neo Avenue, which was the final refuge of the metalwings on the island. According to entomologist D.H. Murphy, a "stand of mature riparian swamp forest in the upper reach of that stream died out at that time."
In the following decades, the streamside vegetation grew back and welcomed fresh recruits of Amphicnemis gracilis and Coeliccia, zygopterans confined to well-shaded wetlands. But this recovery was choked, literally, by a widening of the highway in 1990, which smothered the waterway with fresh layers of silt. Both Amphicnemis and Coeliccia died out in this locality, and even species tolerant of more exposed conditions, such as Onychargia atrocyana and Agriocnemis nana, disappeared from the lower portions of the stream. Only crimson dropwings, a "weedy" species not formerly present, could be found at the site.
The green metalwing, however, never returned, having lost its only remaining habitat of swift, shallow forest streams with a generous bed of weathered boulders and rich patches of riparian greenery. These insects, which still occur in mainland Southeast Asia and Sumatra, present a visual spectacle that cannot but fail to bewitch; M.A. Lieftinck, one of the first early entomologists to see the damselflies in their natural state, as opposed to illustrated pages and faded specimens, called them the "Birds of Paradise amongst Odonata". Males, their bodies and much of the hindwings clad in a "lustre of polished metal", patrol stretches of fast-flowing streams, cruising just above the water with their hindwings often held stiff and still, emitting under direct sunlight flashes of emerald intensity that signal his presence to rivals and mates. At times, they perch briefly on a low pebble, wings closed but still clapping regularly, before resuming flight, which may also take the form of a slow flutter, with the hindwings half-open and a rocking pattern that amplifies the span of their broadcast. Females, which have clear wings with prominent pseudostigmas, typically lurk on streamside vegetation, where they evaluate suitors, form hearts with worthy ones, and submerge themselves fully, sometimes with the mate in tow, to lay their eggs in the stems of aquatic plants or root mats subject to moderately strong currents.
Forest stream, Durian Loop
For Neurobasis, underwater oviposition presents the risk of aquatic predators, violent ripples and drowning. But it also offers the eggs a greater certainty of dissolved oxygen and protection from dipping water levels, as well as refuge from terrestrial parasitoids. Still, long before reaching maturity, each brood must run a gauntlet of foes. Some tiny wasps, whose grubs feast on odonate eggs, have learnt to follow their hosts, using their legs as oars to help them reach buried treats. Water mites insert their rostrums into plant tissue to feast on unhatched embryos.
Young nymphs, if they survive the emphemeral prolarval stage, must evade insectivorous fish, water beetles and their older siblings. Many fall victim to gregarines, protozoans that infest nymphal guts until the passages are fatally blocked or rupture, or succumb to flukes and hairworms that use the insects as intermediate hosts. The survivors must deal with the constant challenge of capturing enough prey to reach the next instar while keeping their heads in favourable conditions, namely waters that are cool, shaded and clean. Towards the end of each cycle, only a handful of naiads, just or barely enough to replace their parents, emerge long before dawn, to crack their shells and rise with the sun.
Neurobasis is known to tolerate disturbed environments, but it seems that what damage took place by the PIE in 1972, be it the runoff of unmitigated roadworks, chemical spills, the removal of larval microhabitats or a combination of these and more, was enough to draw a curtain on this species in Singapore, with the last local individuals seen in 1970. Odonate larva, as noted by Corbet (2004), are far more sensitive to pollution than other aquatic macroinvertebrates, and take a much longer time than their prey to recover from catastrophic incidents. These traits, along with the often fastidious abiotic requirements of species limited to more or less pristine habitats, heap onto the order the thankless status of biological indicator, which the island's last, beleagured population of green metalwings performed to mortal perfection.
Tyriobapta torrida, Venus Drive
The odonates that remain by the streams around MacRitchie Resevoir, from the western upper basin to an unsecured buffer zone in the east, now face a larger threat, one that literally wrecks the foundation of their existence and cuts through the heart of a reserve that is the final stronghold of habitats and creatures at the edge of local existence. Murphy, who explored these invisible wetlands in the 1970s and 80s, characterises higher parts of the basin as "step swamps", as they consist of "uneroded streams" that "alternate between fast flowing reaches and level swampy reaches," a topographical feature of uncertain provenance. Some of the lower regions closer to the resevoir inlets are described as long and narrow "ribbon swamps" that support species associated with swamp forests. There are also "convergence streams and pools" in the Upper MacRitchie basin which provide breeding sites for treehuggers (Tyriobapta torrida) and variable sentinels (Orchithemis pulcherrima), dragonflies regarded as common, but only in such swampy woods, as well as damselflies not, or only rarely, seen elsewhere, such as Argiocnemis rubescens and Teinobasis ruficolis. Also restricted to this zone, on grassy fringes by open streams, is the island's smallest odonate, Agriocnemis nana.
Marshy clearings provide territories for libellulids of open country that fail to thrive in urban pools, such as the red dwarf Nannophya pygmaea, bronze-winged Rhyothemis obsolescens and black-tipped Diplacodes nebulosa. Ceriagrion cerinorubellum, Pseudagrion microcephalum and the latter's scarcer cousin, Pseudagrion australasiae, abound by the reservoir margins and shady inlets, but still rely on bankside vegetation for high roosts. Meanwhile, Cratilla metallica watches over the trails that lead to and through these habitats, guarding its preferred oviposition sites of isolated pools and elevated holes.
Close to the lawns of an anti-country club are flooded terraces criss-crossed by shrubs and trees happy to have their feet wet, on which corduliids such as Epophthalmia vittigera and the much rarer Macromia cincta hang in between forays for small flying insects. These patches of alluvial forest, along with their feeder streams, also harbour species alien and inimical to town parks: Coeliccia octogesima, Archibasis viola, Drepanosticta quadrata, Onychargia atrocyana, Podolestes orientalis, Prodasineura notostigma, Prodasineura collaris, Euphaea impar and Vestalis amethystina – the last two, not unlike their now-extirpated kin, favour water courses of moderately high energy with dirty beds and dense margins, habitats where the hydrology is particularly threatened by invasive infrastructural investigations and downstream developments.
Lestes praemorsus, MacRitchie Reservoir.
MacRitchie Reservoir and its surrounding brooks are also the only known inland locality of Chalybeothemis fluviatilis and Archibasis melanocyana, and where Lestes praemorsus, a delicate, powder-blue spreadwing, was first recorded in Singapore. These and other odonates lacking the adaptations for life in hot, bare waters will not likely survive the physical disruption and erosive trauma to their nurseries caused by investigation machinery or the pressures of subsurface work that may lead to unsustainable fragments as swamps cave in and streams dry up.
As with the ill-fated tributary by the Pan-Island Expressway, new or altered waterways or wetlands may appear over time, but given damage on an infrastructural scale, it is likely that few, if any, of the species lost to months or years of antisocial engineering will return to colonise their old haunts. Instead, those that arrive will consist of more adventurous, almost pelagic, dragonflies such as Rhyothemis phyllis, Trithemis aurora and Pantala flavescens, which already gather at knolls and ridges that rise between the swamps, as well as hunters of exposed parts such as Urothemis signata, Neurothemis fluctuans, Tramea transmarina, Brachydiplax chalybea, Aethriamanta gracilis, Ictinogomphus decoratus and the five species of Orthetrum that roam the still, stewing waters of the reservoir proper.
Murphy, in lamenting the last of Singapore's metalwings in 1999, pointed out the "deteriorating conditions in the Upper MacRitchie Basin" where odonates were concerned, adding that "periods of drought may cause smaller water bodies to dry out entirely with possible long term consequences for species with poor dispersal." Dry spells, or outright destruction of once intact streams and swamps, have already claimed three other victims, Dysphaea dimidiata, Libellago stigmatizans and Orolestes wallacei, which died out between the mid-19th century and the birth of a modern city. The dragons and damsels that remain in the reserves today, whose fate lies on a line of careless underpinnings, are similarly species of mainly stenotopic families: calopterygoids, spreadwings, featherlegs, threadtails and flatwings. These zygopterans, remarked A.G. Orr et al (2004), "move little from their breeding sites and clearing of waterside vegetation may contribute directly to their demise by denying them a source of adult nutrition." Orr, echoing Murphy in observations that probably apply throughout the region, added, "Both stenotopic and eurytopic species show promise as indicators of environmental disturbance as the latter tend to invade pristine forest areas following perturbation, while the former disappear."
The prospects are likewise bleak for other freshwater taxa. Two palaeomonid shrimp, Macrobrachium neglectum and Macrobrachium idae, are reported to have been common in streams outside the Nee Soon Swamp Forest until the 1980s, but have since become very rare owing to the loss or modification of downstream habitats, which are required for their larval development. Their eventual, if not effected, extinction is hence predicted, conservation efforts notwithstanding, in the wake of what befell a larger prawn, whose catadromous life-cycle was cut short by canals that hindered its reproductive movements. Stenotopic water beetles, even populations in primary habitats, are "on the verge of local extinction", while swamp forest-dependent aquatic hemipterans, having lost three species to the taming of Sungei Seletar, face the triple threats of "change, loss or pollution" to jungle streams. Paradise, be it a bird or merely a beauty on the wing, may not surrender to a parking lot. It is far easier, in a country with little hindsight and fewer regrets, to plan for a future with no room for error and every possibility of mistakes that can never be paved over.