We still have a lot of river work to do

Kapiti News - - News -

I’m con­tin­u­ing on from last week’s col­umn on GWRC’s re­port Are we meet­ing our en­vi­ron­men­tal out­comes on the Ka¯ piti Coast?

The Ka¯ piti Coast is full of seem­ing con­tra­dic­tions. It has a cli­mate that is the envy of much of the rest of the re­gion, yet is the most sus­cep­ti­ble to cli­mate change. Just over half of the catch­ment area re­mains vir­tu­ally un­touched, yet the coastal low­lands are al­most 100 per cent mod­i­fied. It con­tains two big, beau­ti­ful rivers that are sur­rounded by a num­ber of small, de­graded streams. It boasts long, pris­tine beaches but has one of the most de­graded lakes in the coun­try. It can ex­pe­ri­ence very dry sum­mers, but is prone to flood­ing at other times of the year.

Three key is­sues stood out in the re­port as re­quir­ing im­me­di­ate at­ten­tion.

Firstly, the im­pacts of cli­mate change: un­der cur­rent pre­dic­tions of sea level rise, parts of the Ka¯ piti Coast could be per­ma­nently in­un­dated by the end of the cen­tury. But this is not the worst of it.

The big­gest threat to the coast will be the com­bined ef­fects of more in­tense storms, high tides and sea level rise. In the fu­ture, west­erly storms com­ing from the Tas­man Sea will get sig­nif­i­cantly worse, bring­ing heav­ier rain and stronger winds.

Fur­ther, the coastal dune sys­tems, the first line of de­fence against coastal in­un­da­tion, have been di­min­ished by ur­ban devel­op­ment and de­graded by the in­va­sion of ex­otic plant species.

Sec­ondly, soil qual­ity at mar­ket gar­den sites: ex­ces­sive lev­els of phos­pho­rus in soil are a re­gion-wide prob­lem and the Ka¯ piti Coast is no ex­cep­tion.

How­ever, when it comes to mar­ket gar­den sites, the si­t­u­a­tion is a bit more se­vere. Over half the sites GWRC mon­i­tor have de­pleted lev­els of or­ganic mat­ter, which is es­sen­tial for re­tain­ing mois­ture, nu­tri­ents and good soil struc­ture. And nearly three quar­ters of the sites have low struc­tural sta­bil­ity, mean­ing they are more prone to des­ic­ca­tion (be­com­ing com­pletely dried out), break­down and ero­sion.

How’s this for a scary fact: soil is con­sid­ered a non-re­new­able re­source — once it has been de­stroyed, it is lost for­ever.

Thirdly, wa­ter qual­ity, par­tic­u­larly small streams: all of the streams GWRC mon­i­tors on the Ka¯ piti Coast ex­hibit, with­out ex­cep­tion, poor wa­ter qual­ity and de­graded ecosys­tem health.

And let’s not for­get Lake Waitawa (north of O¯ taki), which is also in poor con­di­tion and ranked 197th out of 259 lakes na­tion­wide.

We can­not af­ford to be com­pla­cent about the O¯ taki and Waikanae rivers ei­ther. While they cur­rently have very good wa­ter qual­ity, they are both show­ing signs of degra­da­tion at their bot­tom ends.

Let’s not kid our­selves, we have a lot of work to do.

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