Topical Essays

A Darkness at Noon

‘They meet darkness in the daytime, and grope in the noonday as the night’ Job 5:14

Allegories are a powerful way of getting points across, but between the general and the specific there is always a bridge to cross. Koestler’s 1940 book with the title of this essay was about the circular nature of perfidy in totalitarian governments around World War II, while Job’s was more of a fire and brimstone lesson. Neither was a paean to joy!

It’s easy to fall into the same doomsday trap when reading about the relentless and harrowing scenarios about climate change. We generally feel helpless as individuals about mitigating sea level rise and a heating planet because the connection between our own paltry efforts and any global action of millions is diffuse. But there are always things we as smaller groups can do closer to home that will make a real difference to earth’s ecosystems, such as a focus on ‘manageable stressors’. One of the more impactful of these is the increasing flow of sediments and contaminants from land into New Zealand’s rivers and coastal marine environment. These sediments cloud the waters and cover the sea floor, damaging the very infrastructure necessary for our marine ecosystems to survive and thrive. The finer fractions of these sediments remain suspended in coastal waters, making them so dark and of such poor spectral quality that they do not provide the necessary light for many of our submerged kelp forests to grow – even in broad daylight. Coarser fractions of sediment accumulate on subtidal rocky reefs, smothering the kelp forest species that live there and preventing new individuals from settling and attaching. In combination, therefore, two of the most important requirements for kelp forests – a place to settle and sufficient light to grow – are diminished or missing along parts of our coastline.

A river plume entering Pegasus Bay, Christchurch (photo from The Press)

We have done poorly in managing such sediments. They accumulate on the sea floor over time, and are often delivered in huge pulses from intense rain events that sweep soils from land in many river catchments around our 11,000 kilometres of coastline. We’ve all seen it. Large brown plumes sweeping out to sea from rivers, the ‘brown line’ we see when flying along the coast, the slash, mud and debris washed into river mouths from cleared land and harvested forests. The major consequences may be invisible to most people, but they can be dire for marine life.

Few people other than marine scientists know that on a per-area basis, our coastal kelp forests support the greatest biodiversity of New Zealand’s ecosystems. A typical square metre of rocky reef can have over 50 species of seaweeds, sponges and other colourful filter-feeding attached organisms, and many small invertebrates. Filter-feeders remove bacteria and contaminants from the water, and mobile invertebrates such as shellfish and crabs eat algae and kelp fragments that break off in wave action. The invertebrates are eaten by a diverse array of coastal fishes, to such an extent that up to 40% of the mass of a fish is directly derived from kelp via the coastal food web. Kelp itself can have double the primary productivity of equivalent areas of pastureland, which means that it’s a major carbon store. And all of this production is based on life’s miracle of photosynthesis – converting the sun’s photons to energy and growth. With insufficient light, this process is diminished or ceases altogether, whether or not there is bright sunlight above the waves.

Sediment plumes around Kaikōura

The Marine Ecology Research Group has been studying rocky reef diversity and its drivers for many years. As early as the mid-2000s, we have highlighted the pervasive effects of sediments on important algae and kelp communities. Some of our pioneering work helped to unravel the relationship between the spectral qualities and amount of light, production of kelp, and synergistic effects of diverse algal communities on primary productivity. Because of reduced water clarity to deeper reefs, it is now certain that some algal assemblages have diminished over time, retreating into shallower water where light is less limiting — a phenomenon also seen in other countries with severely sedimented coastal waters. The situation is alarming and getting worse – but thankfully it’s not yet terminal.

We as a nation need to take on the hard environmental issues of managing our coastal ecosystems with greater purpose and focus. Protective tools such as marine reserves may help, but these have mostly to do with the creation of refuges from fishing pressure and do not deal with cross-ecosystem impacts from activities on land. Unfortunately, the ‘darkness at noon’ in marine waters is largely invisible from a terrestrial perspective. It is also largely invisible to science funders, who have other pressing problems. However, we need to think more about ‘holistic’ management, from land to sea. In particular, we need to manage land uses better – agriculture, cities, forestry –to reduce sediment and contaminant flows off land to the sea. And we need to answer questions such as ‘How much sediment reduction or change of land-based practices is enough to improve rocky reef communities along our coast’?

Where’s the kelp?

Many people argue that we must simply stop engaging in some practices, but this almost always comes with economic costs, and often to hard-hit rural and coastal communities. It is much better, then, to see what we can do to work collaboratively so that the real costs of each activity are not borne by our spectacular kelp forests and diverse marine communities, which are iconic biodiversity hotspots and a provider of seafood, recreation and cultural values. To do this, we need more targeted science to produce of toolbox of modern techniques – remote sensing, environmental chemistry, state-of-the-art in situ monitoring — that will allow real-time assessments of new management actions to ensure that they work. Too often, our performance metrics are that we developed new techniques or tried this or that to improve some practices on land. Instead, we need to shift the focus on measurable improvements to our coastal ecosystems. This, in fact, is what regional managers are responsible for doing. We hope our work that couples the collective endeavours of scientists, iwi, industry and managers will produce measurably improved outcomes for our kelp ecosystems.

We have plenty of problems with warming seas, rising sea levels, heat waves, and other climactic events, but let’s fix the impacts that are more readily manageable. After all, much of our well-being and economy depends on the invisible part of our ecosystem along our vast shoreline. For our common good, it needs to be more visible above and below the waves. To paraphrase another saintly sermon, where there is darkness, let there be light.

20 December 2021

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Further reading

Tait, L.W. and Schiel, D.R., 2011. Legacy effects of canopy disturbance on ecosystem functioning in macroalgal assemblages. PLOS one, 6(10), p.e26986.

Tait, L.W. and Schiel, D.R., 2011. Dynamics of productivity in naturally structured macroalgal assemblages: importance of canopy structure on light-use efficiency. Marine Ecology Progress Series, 421, pp.97-107.

Tait, L.W., Orchard, S. and Schiel, D.R., 2021. Missing the forest and the trees: Utility, limits and caveats for drone imaging of coastal marine ecosystems. Remote Sensing, 13(16), p.3136.

Schiel, D.R., Gerrity, S., Orchard, S., Alestra, T., Dunmore, R., Falconer, T., Thomsen, M. and Tait, L.W., 2021. Cataclysmic disturbances to an intertidal ecosystem: Loss of ecological infrastructure slows recovery of biogenic habitats and diversity. Frontiers in Ecology and Evolution, p.827.

The People Love Pāua (but maybe too much)

Today (1 December 2021) is when the pāua fishery opens along the Kaikōura coast after 5 years of closure. This is joyful news to those who love the black-footed delicacy and are now able to fish for it legally for the first time since the Kaikōura earthquake. To them, it’s a case, of ‘Let the Fishing Begin!’. To others, however, it’s a case of ‘Let the Pillaging Begin’.

Easy pickings, but how long will they last?

A balance between a fishery and sustainability is always difficult to achieve. Because of the vagaries of climate and the environment, interacting with reproduction, recruitment and growth of fished species, there are no constants in fishery production. There are always boom and bust years, and these are overlain by fishing pressure. There is also a dynamic balance between the recreational, cultural and commercial components of the catch. Achieving this balance is especially difficult for pāua, which are readily accessible in the low intertidal and shallow subtidal zones. This means that almost anyone can harvest them with little or no fishing or diving gear.

To control the fishery, it is a matter of establishing a catch limit (the ‘Total Allowable Catch’) that the fishery can sustain and then allocating it proportionally among the fishing sectors. Let’s put aside how this is done – but there is a detailed science-informed and consultative process involved. The real problem is that there are different controls and reporting in the three sectors of the fishery.

Commercial fishers must report number, sizes and locations of catches within their specified quota areas. Cultural fishers must have permits issued by local guardians that specify numbers caught and locations. Together, these provide fairly exact figures on pāua removed from coastal populations. The recreational fishery is more problematic. No licences, permits or reporting are required. There is a daily catch limit of 5 pāua per person per day, but no limits on the number of people who can fish and get that daily limit, or on how many times they can go out and take the daily limit. There is an ‘accumulation limit’ of 10 pāua, but it’s very difficult to enforce. Therefore, the size of the recreational fishery is at best a guesstimate. It could ostensibly exceed the other components of the fishery and far exceed the figure that is designated as the Total Allowable Catch. Without any catch reporting for recreational fishing, it’s impossible to know for sure. And then there is the illegal fishery, where people take pāua beyond the catch limit or under the size limit. Unless they are caught by vigilant Fisheries Officers, it is hard to know the extent of the illegal ‘fishery’, but it can be substantial for easy-to-catch species like pāua.

The Marine Ecology Research Group has been monitoring recruitment and growth of pāua and the condition of habitat at 26 sites along 140 km of coastline between Oaro and Cape Campbell since the 2016 earthquake. Pāua populations were hit particularly hard initially because of the uplift of coastal reefs, and there were serious concerns about their recovery. The good news is that pāua populations recovered well and there are now large numbers of legal-size individuals (>125mm shell length) along the rocky coastline. One problem for the fishery, however, is that it takes 6 years or so for pāua to reach legal size after they drop out of the plankton as larvae. After intensive fishing pressure removes the vast majority of large pāua, and the older individuals are fished down, the fishery must rely on new recruits coming through.

The problem of recreational fishing pressure is now beyond latent for many species – it is real and pressing. In the end, once a fish is caught, it doesn’t matter which sector took it – it no longer contributes to natural populations and future recruitment. Those are biological facts that must be accommodated for sustainable fishing, and for leaving something for our kids and future generations. (14 Dec 21); illegal catch of 249 pāua, 111 of which were under the legal catch size

It comes down fundamentally to simple statistics. New Zealand’s human population is going up, the number of fishers is increasing, but the pāua fishery is at best stable at a particular level. This means that recreational fishing pressure increases, even as pāua decrease or remain stable. We as a nation will not achieve sustainable fishing for inshore species such as pāua unless we get real reporting on recreational catches. Other countries have developed non-intrusive schemes for reporting catches, such as phone apps, with the requirement of placing an issued tag on each individual taken. There is resistance everywhere to such schemes but, in the end, it is a relatively simple and achievable way for people to get their catch limit, and for fishery managers to know how many fish are taken so that total catches can be known and managed sustainably.

What will happen to the newly opened Kaikōura pāua fishery? We’ll be able to tell you after the initial season closes at the end of February. If history is anything to go by, there may well be some debate about who took what, where, and whose right it is to take the lion’s share. The initial three-month open season has begun for pāua. When we re-survey populations after it closes again, we’ll have a good idea whether it was a case of fishing sustainably or more like plunder of this readily accessible and prized species.

1 December 2021

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Further reading:

Gerrity, S., Alestra, T., Fischman, H.S. and Schiel, D.R., 2020. Earthquake effects on abalone habitats and populations in southern New Zealand. Marine Ecology Progress Series, 656, pp.153-161.