New Zealand's destiny is inextricably tied to that of its celebrated environment. But our blue and green backyard is now under unprecedented pressure from a wave of pests and human activity, ranging from development and pollution to climate change and tourism. In the final part of our week-long series, 50 Questions About the Environment, the head of University of Auckland's Institute of Marine Science, Professor Simon Thrush, discusses our ocean ecosystems with science reporter Jamie Morton.

The Ministry for the Environment and Statistics New Zealand's most recent report showed our marine estate was under pressure, with most of our native marine birds and many mammals being threatened with, or at risk of extinction. What are the main drivers and how have trends changed over recent decades?

Our native marine birds and mammals face many threats, and for those species that range over vast areas of ocean part of the problem may not be under our direct control.

But that should not stop us reducing the stress on these species within our waters.

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Pressures associated with fishing - both incidental mortality and changes in access to food and nursery areas - are critical and for many of our birds loss of nesting and roosting sites and increased predation on land are major threats.

But just like the myriad of other marine species that live in our oceans and on the seafloor it is the cumulative effects of multiple threats that is the real problem.

It's all too easy point the finger of blame at one activity but the combination of different stressors can threaten species at level that one factor alone would not.

So it is about fishing, habitat change and other factors such as plastic pollution and climate change - all important.

Of course not all the threats will have the same intensity across our vast marine estate.

So we need to take a much more ecosystem-based approach to addressing these threats.

You could argue that one of the main pressures is generated by the way we try to manage both species and threats in a piecemeal fashion.

The report also found, perhaps unsurprisingly, coastal ecosystems are under the most pressure from human activities. Why are these areas such a critical part of our marine environment?

Coastal ecosystems are really important to us in so many ways, but squeezed between the land and the open sea they have to cope with multiple threats.

From a very human perspective these places are important because we interact with them so much.

Particularly in our urban areas, these are some of the few wild places we can easily access.

New Zealand's first marine reserve at Leigh, north of Auckland, has shown how marine protected areas can make a difference. Photo / File
New Zealand's first marine reserve at Leigh, north of Auckland, has shown how marine protected areas can make a difference. Photo / File

However, coastal ecosystems are hothouses of activity that plays an essential role in transforming nutrients and organic matter that come off the land, they are also important sites for both processing and storing carbon - all ecosystem processes that help us mitigate the impacts of climate change and eutrophication.

Coastal ecosystems are highly productive providing food resources for us and many other marine species.

So what impact is fishing - commercial and recreational - generally having on our marine ecosystems? And do you feel our quota management system and other regulatory frameworks are performing well enough to sustain stocks?

There is no doubt that fishing can have a major impact on marine ecosystems, whether it's commercial or recreational.

Of course the extent of the impact will depend on how and how much we catch, as well as the other stressors the ecosystem is facing.

Much of the way we manage fisheries is based on concepts developed at a time before we understood how ecosystems work as well as we do now.

Since its introduction the quota management system has evolved and helped address some problems in fisheries management.

But it is an expensive process to run properly and has a number of unintended consequences.

Most importantly, it has been viewed as the solution to all fisheries management problems, which it isn't.

READ MORE: Do we need an oath to protect oceans?

It has also prevented us managing across activities - accumulating the risks of multiple stressors.

This has meant we have fallen far behind in terms of addressing many issues in marine resource management.

Ocean acidification and warming may cause widespread harm to marine ecosystems, for example, by reducing the survival and growth rates of marine species, extending or reducing the range of species, and modifying habitats. In New Zealand waters, are we starting to see any of these effects already?

We are seeing changes in ocean chemistry in parts of New Zealand consistent with ocean acidification, and in some places we are seeing trends of increased wave activity associated with climate change, but in other places these changes are not apparent.

This all makes sense when you think about the wide range of ocean climates around New Zealand.

As far as I know we have not seen ocean acidification effects on individual species, biodiversity or ecosystems outside the laboratory.

This could easily be that we lack good ecological data to detect these changes – the lack of good data is another important message from the Ministry for the Environment and Statistics NZ report we discussed earlier.

The place we need to be in is one where we are planning carefully about how we can mitigate or adapt to these future changes.

When we think of global warming it's easy to get overwhelmed by the problem, but particularly in the coastal zone there are things we can do.

Acidification process do not work in isolation, the way we add nutrients and organic matter to the coast makes a huge difference.

Limiting the potential for eutrophication, maintaining and restoring critical habitats will help the capacity of our coastal ecosystems cope with these global issues.

Pollution from plastic waste, such as single-use bags and microbeads, has also increasingly become a talking point, with high profile figures such as freediver William Trubridge highlighting its impact on our oceans. What do we know about the level of plastic pollution in New Zealand's ocean environment?

Yes we hear reports from around the world of plastics being found everywhere from the deepest parts of the ocean to deserted Pacific Islands.

It's ironic that one of the earliest studies documenting tiny plastic particles in marine sands came from a study in Auckland, but we do not yet have data on the abundance of microplastics.

"For the larger bits of plastic waste there are many groups doing great work with beach and harbour clean-up programmes - and it's staggering how much material they pick up." Photo / File

We have just started a study on this in Auckland.

For the larger bits of plastic waste there are many groups doing great work with beach and harbour clean-up programmes – and it's staggering how much material they pick up.

As important as knowing how much is out there and where it's accumulating is understand what the plastics, especially microplastics, do in our marine environment.

This is part of our new project, but we know from overseas research that microplastics do not just fill the guts of marine animals but often carry other chemicals into the animals and have a range of effects on the health of these organisms.

Over recent times we've seen a greater push for marine reserves and marine protected areas around our own coasts, and across larger areas of oceans, including the new Ross Sea MPA and a giant sanctuary proposed for the Kermadecs. What difference do these havens make - and is it meaningful when set against the larger pressures being put on oceans?

Marine Protected Areas are profoundly important both in terms of ecology and in how we think about and take responsibility for our marine estate.

It's easy to think that with all these stresses on the marine environment that MPAs are not going to be much help, but I think this is wrong.

It is frequently the combination of threats that is most problematic and the use of MPAs can provide the capacity in biological systems to respond to change.

The size and numbers of areas protected also helps us hedge our bets.

Even our small coastal reserves, such as then one at Leigh, have shown remarkable benefits to the local ecosystem and spill over effects on adjacent snapper stocks.

As important as these benefits to the marine ecosystem are, the societal benefits are also important.

READ MORE: How will climate change hurt ocean species?

Large scale marine spatial planning shows we are taking responsibility for our marine estate.

The fishing industry has come in for criticism over the welfare of endangered NZ sea lions. Photo / File
The fishing industry has come in for criticism over the welfare of endangered NZ sea lions. Photo / File

No longer should the marine environment be treated as a wild frontier ripe for exploitation, that's got to be a good place to start thinking about how we balance all the different ways we use and benefit from our coasts and oceans.

Of course the devil is in the detail and we have to make sure we design MPAs and MPA networks effectively and combine them with other appropriate tools for marine management and conservation.

New Zealand has a sprawling marine estate, covering more than 4m sq km and an area 15 times the size of our country. Scientists have estimated 65,000 species could be found within it - we know of only about 15,000 presently - and less than one per cent of it has been fully surveyed. Given this, and the fact we are a small nation, how challenging is it for Kiwi scientists hope to gain a deep understanding of our marine environment? And what are those burning questions that we urgently need to answer now?

Of course this is a huge challenge, but we continue to find fascinating new species, new habitats, new relationships between organisms and develop our understanding the processes that drive ecosystems and dictate their response to change.

This understanding forms a reservoir of knowledge and local capacity to address the challenges of the future, some of which we can expect while others will surprise us.

We need to get the basics right as well as work on solutions to the issues of the day.

We are a small country but science is a very international enterprise - we can work with our colleagues to address many common problems and learn from each other.

READ MORE: NZ's oceans are under rising pressure - report

Colleagues in developed nations need us to be able to make a useful contribution to the research, while colleagues in developing nations need support to help them grow their strengths.

Numbers of sooty shearwater have been declining over recent decades. Photo / File
Numbers of sooty shearwater have been declining over recent decades. Photo / File

All this means that for a small country we need to have good ways of allocating science funding and ensuring it is invested in problem solving and finding solutions.

In terms of the burning issues of the day, I think there are important knowledge needs in relation to all the issues we have discussed.

But there are some bigger overarching issues that I think we need to take seriously for instance: How do we restore marine ecosystems?

How do we learn to value and take responsibility for these ecosystems? How do we actually implement ecosystem-based management?

How can we expect marine ecosystems to respond to global change and how will this affect the environmental, cultural and economic benefits we derive from them into the future?

These kinds of questions require that we really understand how marine ecosystems work, but also open up a range of other questions about trust in science, policy, governance and law.

Some research now being carried out by Kiwi scientists look at the specific issue of ocean "tipping points". What are these?

We hear the term tipping point used frequently now and in many different contexts.

From an ecological perspective, a tipping point represents a sudden and dramatic change in the way an ecosystem works.

For example, we could lose an important natural resource, such as a fish stock, without having changed the fishing effort, or we could see an improvement in an ecosystem, such as a decrease in how muddy the water in one of our harbours looks, with restoration of shellfish beds.

"There is no doubt that fishing can have a major impact on marine ecosystems, whether it's commercial or recreational." Photo / File

In other words we can think about tipping a system up or down, unfortunately degrading is usually easier than improving the ecosystem.

The most fascinating thing about working on tipping points is that just a small change can have big consequences.

This forces us to really think about how ecosystems work and the cumulative effects of change.

It also questions the way we think about managing ecosystems for example by managing down to a set limit or dealing with individual problems in isolation.

Do you feel Kiwis are generally aware of our marine environment and the abundant biodiversity within it?

I am lucky to interact with a lot of people who value our oceans, whether they are scientists, divers, photographers, fishers or conservationists.

But for many the ocean is taken for granted, its stretches to the horizon how could be possibly affected by this one new activity - or by the same activity we have always done – this is an all to common view.

We do need to grow our awareness of the marine environment and how we are changing it and what the consequences for us might be.

Ultimately, is it possible for us to strike a healthy balance between our own activities - industrial and otherwise - with the marine environment?

I do not see we have any other alternative but to figure this out and fast.

In the past humans have often considered the oceans an inexhaustible resource, we now know this is not true.

But we cannot do this by ourselves and we need to be open to working on this collective problem – after all we are talking about seven tenths of the surface of planet Earth.

The Series

Monday:

Our rivers

Tuesday:

Our nature

Wednesday:

Our climate

Yesterday:

Our biosecurity

Today:

Our oceans