A BUT­TER­FLY VIEW OF THE ROYAL CANAL

A re­framed fo­cus on a fa­mil­iar land­scape re­veals myr­iad as­pects of na­ture’s web

The Irish Times - Weekend Review - - ENVIRONMENT - Paddy Wood­worth

The last refuge of na­ture in our over­crowded world is of­ten, iron­i­cally enough, to be found in ob­so­lete rem­nants of hu­man in­dus­try. Our canal sys­tem is a mon­u­ment to Vic­to­rian engi­neer­ing, but these ar­ti­fi­cial wa­ter­ways no longer carry com­merce from town to town. Mean­while in­ten­sive farm­ing, with its pes­ti­cides, her­bi­cides and fer­tilis­ers has, bi­o­log­i­cally speak­ing, im­pov­er­ished the soils of the agri­cul­tural land around the canals. So the path­ways and hedgerows along­side their banks have in­ad­ver­tently be­come sanc­tu­ar­ies for the great va­ri­ety of wild flow­ers that can no longer sur­vive in in­dus­tri­alised graz­ing and ce­real sys­tems.

One of the last places in Cos Dublin and Kil­dare where you can still find the char­ac­ter­is­ti­cally rich plant life of cal­care­ous ( lime­stone- based) grass­land is along the banks of the Royal Canal. And with these plants come a host of as­so­ci­ated life-forms, from but­ter­flies to birds, once abun­dant in these land­scapes, now of­ten also re­duced to these ac­ci­den­tal ar­ter­ies of bio­di­ver­sity.

The idea that the nat­u­ral world is a web, in which ev­ery­thing is con­nected to ev­ery­thing else, lies at the heart of ecol­ogy and has be­come com­mon­place in our na­ture ed­u­ca­tion. But there are myr­iad in­ter­linked strands in this web, and many of them are not at all ob­vi­ous – un­til some­one points them out to you. Grasp­ing a fresh set of such con­nec­tions di­rectly is al­ways a spe­cial plea­sure, and re­frames the way we look at fa­mil­iar places.

Wealth of species

Jes­mond Hard­ing is a good man to re­frame your view of a canal bank in early May. At first sight, the veg­e­ta­tion is still mostly an un­ex­cep­tional mud­dle of green leaves but Hard­ing deftly iden­ti­fies a wealth of species, link­ing most of them to the life-cy­cle of par­tic­u­lar but­ter­flies.

Oc­ca­sion­ally, the but­ter­fly’s com­mon name will give a clue to one of its host plants. A holly blue ap­pears, flit­ter­ing oblig­ingly over a holly bush. Hard­ing says that this gen­er­a­tion will lay eggs on the holly’s ten­der fresh leaves, per­fect food for its cater­pil­lars. By mid­sum­mer, how­ever, the leaves will be too tough. So the next gen­er­a­tion will lay on ivy, and the cater­pil­lars will feed on its emerg­ing berries.

Hard­ing is a school­teacher, and ex­hibits the best of his pro­fes­sion’s abil­ity to rapidly com­mu­ni­cate facts through in­fec­tious en­thu­si­asm. He has been in­ter­ested in birds since the 1980s, but more re­cently be­came fas­ci­nated by but­ter­flies, and helped found But­ter­fly Con­ser­va­tion Ire­land.

So the way he views the canal­bank veg­e­ta­tion is fo­cused through the lens of these crea­tures, ex­tra­or­di­nary not only in their beauty but in their two rad­i­cally dif­fer­ent lives, first as crawl­ing plant­ing-eat­ing cater­pil­lars and then as fly­ing nec­tar-feed­ers.

One of the few plants al­ready in flower where we are walk­ing the canal bank, near Louisa Bridge at Leixlip, is the cuck­ooflower, also known as lady’s smock. Its vari­able lilac, pink or white blos­soms are fa­mil­iar in wet­lands. I was vaguely aware that it was as­so­ci­ated with the orange-tip, a small white but­ter­fly with vividly con­trast­ing wingtips. And sure enough, we see an orange-tip flick­er­ing away within min­utes of first see­ing the cuck­ooflower. Hard­ing is able to show me ex­actly where to find the orange-tip’s eggs, tiny green ovoids ad­her­ing just be­low the blos­som where the seed pod de­vel­ops.

A few min­utes later, we visit the re­mark­able land­scape of a for­mer spa, along­side the Louisa Bridge rail­way sta- tion sec­tion of the canal. This is a Spe­cial Area of Con­ser­va­tion, and is rich in wet­land plants such as bog cot­ton, the car­niv­o­rous com­mon but­ter­wort, a small galaxy of bog­bean in spec­tac­u­lar bloom – and more cuck­ooflow­ers.

Above them, a green-veined white but­ter­fly dips and rises. Hard­ing ex­plains that this species also uses the cuck­ooflower to host its eggs – and to feed its cater­pil­lars. But it lays eggs not on the seed­pod, but on the rosette of leaves at the base of the plant. This is an ex­am­ple of “ecological sep­a­ra­tion”, whereby nei­ther but­ter­fly need com­pete with the other.

Nearby, Hard­ing iden­ti­fies two speck­led wood but­ter­flies en­gaged in what I have al­ways taken to be an el­e­gant, spi­ralling courtship dance. But Hard­ing gen­tly cor­rects me. These are two males, dis­put­ing ter­ri­to­rial rights. “They have no bit­ing body parts,” he says, “but they can knock scales off each other’s wings.”

Ev­ery­where along the bank, Hard­ing iden­ti­fies more plants whose leaves (or berries) feed cater­pil­lars, or whose flow­ers pro­vide nec­tar for but­ter­flies – mead­owsweet, resthar­row, meadow vetch­ling, wild mar­jo­ram and many more. You might dis­miss that patch of net­tles as “weeds”, but it is prime but­ter­fly habi­tat. A pea­cock but­ter­fly set­tles nearby to feed on an el­der­flower in the hedgerow. Hard­ing thinks it’s a fe­male from its size. To check, he tosses a small stone, so that its shadow moves rapidly over the leaves near the but­ter­fly. It does not stir. “Def­i­nitely a fe­male,” he says. “A male would have taken off in pur­suit of the shadow, hop­ing to find a mate.”

When you see a but­ter­fly flut­ter­ing over flow­ers with­out paus­ing to feed, he says, it is usu­ally a male, search­ing for a fe­male freshly emerged from a chrysalis. The fe­males may emit a pheromone – a chem­i­cal sig­nal to in­di­cate their pres­ence – but this has still to be con­firmed by science.

The male has to be quick off the mark, be­cause the fe­male will usu­ally only mate once in her life cy­cle. A sin­gle batch of sperm will en­able her to lay suc­ces­sive sets of eggs over the next few weeks. Hard­ing says, how­ever, that there is some ev­i­dence now that some fe­males mate twice, and that those that do may live longer; food for thought, per­haps.

But even as Hard­ing re­veals the mul­ti­ple quirks and con­nec­tions of the web of life around us, he ex­presses anx­i­ety that this rich and threat­ened ecosys­tem is threat­ened by the plans of a State agency, Wa­ter­ways Ire­land, to “im­prove” pub­lic ac­cess to the canal banks. His con­cern is shared by walk­ers and na­ture lovers along the Bar­row and else­where. This is­sue, and Wa­ter­ways Ire­land re­sponse, will be the sub­ject of a fu­ture ar­ti­cle on this page.

MAIN PHO­TO­GRAPH: FRAN­CIS BRADLEY

In a flap on the Royal Canal. Be­low, from top: Holly­blue, Comma Hutchin­son, Brim­stone, Orange tip and Pea­cock but­ter­flies.

Ter­ri­to­rial rights

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