Short drop amid the flames

The Press - - Catalyst - Will Harvie will.harvie@stuff.co.nz

Clever new re­search con­firms that huge fires that burned across the South Is­land shortly af­ter the ar­rival of Poly­ne­sians were in­deed set by hu­mans.

While it’s long been as­sumed that the fires were prob­a­bly started by early ar­rivals, proof has been lack­ing and it was pos­si­ble that hu­mans and fires were co­in­ci­den­tal.

But stud­ies of sed­i­ments in two lakes near Wanaka and Queen­stown turned up hu­man fae­cal mat­ter in the same lay­ers as char­coal and ash from early fires.

‘‘Our data pro­vide a di­rect record of lo­cal hu­man pres­ence in Lake Kirk­patrick and Lake Di­a­mond wa­ter­sheds at the time of de­for­esta­tion and a new and stronger case of hu­man agency linked with for­est clear­ance,’’ re­ported lead au­thor Elena Ar­giri­adis of the Uni­ver­sity of Venice.

The team of nine re­searchers from Italy, the United States and New Zea­land – in­clud­ing Janet Wilmshurst of Landcare Re­search and the Uni­ver­sity of Auck­land – took sed­i­ment sam­ples from the two rel­a­tively re­mote and undis­turbed lakes.

As ex­pected, they found lit­tle ev­i­dence of wide­spread burn­ing be­fore AD1280, the year western sci­en­tists date the first ar­rival of Poly­ne­sians in Aotearoa, plus or mi­nus 20 years.

Be­fore then, there were ‘‘nearly un­de­tectable’’ sam­ples of burn­ing, pre­sum­ably from fires set by light­ning and ash blown across the Tas­man Sea. But the podocarp forests of the area burned very lit­tle.

About 1350, how­ever, that changes. Ev­i­dence of fire ‘‘abruptly and si­mul­ta­ne­ously in­crease[s] in sed­i­ments at about AD1345–1365 and mark[s] a pe­riod of in­tense or mul­ti­ple fire events,’’ the authors re­ported in the pa­per pub­lished in the jour­nal Sci­en­tific Re­ports.

‘‘The peaks oc­cur shortly af­ter Ma¯ ori ar­rival and dur­ing the Ini­tial Burn­ing Pe­riod.’’

The re­searchers also found co­prostanol and re­lated sub­stances. Co­prostanol is the most abun­dant sterol in hu­man fae­ces and lasts for cen­turies in the right en­vi­ron­ment.

‘‘Prior to hu­man set­tle­ment, fluxes of fae­cal sterols in both lakes were near zero,’’ the authors re­port.

There were sub­stan­tial in­creases in hu­man fae­cal sterols be­tween 1310 and 1380, match­ing strong ev­i­dence of nearby fires.

It’s thought the fae­cal mat­ter was de­posited on the ground and runoff moved it into the lakes.

The record shows a short­lived peak of fae­cal sterols and ‘‘sug­gests that hu­man ac­tiv­ity in the wa­ter­shed lasted only a few decades’’.

Af­ter that, fae­cal val­ues re­mained about twice the level found in the pre-Poly­ne­sian era, the authors wrote.

‘‘This de­cline be­tween about AD1400 and 1800 likely marks a re­duced pres­ence of peo­ple in the wa­ter­shed prior to Euro­pean coloni­sa­tion, although hu­mans may have been present spo­rad­i­cally or in low num­bers.’’

Pollen and other plant mark­ers were also ex­am­ined and showed a dra­matic change in the veg­e­ta­tion in the area. There was fewer na­tive podocarps and more fire-adapted shrubs, grasses and ferns.

Lake sed­i­ments also showed greater ero­sion af­ter the ini­tial burn­ing.

Ar­chae­ol­o­gist Atholl An­der­son and other Ma¯ ori schol­ars have found ev­i­dence of ku¯ mara cul­ti­va­tion as far south as Kaiko¯ ura and pos­si­bly even Banks Penin­sula, but in­land Otago would have been too cold. South­ern Ma¯ ori were for­agers who con­tin­ued to burn land­scapes to ‘‘pro­mote key car­bo­hy­drate re­sources, such as fire-adapted bracken fern’’, es­pe­cially once food re­sources like moa birds were ex­tinct.

South­ern Ma¯ori were for­agers who con­tin­ued to burn land­scapes to pro­mote key car­bo­hy­drate re­sources.

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