We know Aotearoa New Zealand is home to many geographically and biologically special features. Yet few of us know it also has its very own measure of “deep time”.

Known as the New Zealand Geological Timescale, it has just undergone its most comprehensive revision in 20 years.

Like the periodic table, the geological timescale brings order to Earth’s deep history, measuring millions of years of time recorded in the rocks beneath our planet’s cities and towns, mountains and rivers.

It has been described by American writer Marcia Bjornerud as “one of the great intellectual achievements of humanity”.

For more than a century, New Zealand geologists and palaeontologists have maintained their own scale because the international timescale, developed largely in Europe and North America, has been difficult to apply elsewhere.

Even today, most boundaries in deep time are defined using fossils. Most New Zealand fossils, as with our living plants and animals, are found nowhere else.

The revised New Zealand version updates the ages of the timescale’s divisions and removes many long-standing ambiguities in how they are defined.

As a result, it will improve our understanding of both the geological gifts and the geohazards of life on the “shaky isles”.

Looking beyond the human timescale

In one sense, deep time is the antithesis of the short-term view that drives political and economic cycles.

To properly understand climate change, mass extinction or ice-sheet collapse – processes that carry profound implications for humanity hundreds to thousands of years from now – we need to step beyond the limited perspective of direct human experience.

This is also important for how we think about natural hazards.

The explosive eruption of the Hunga Tonga–Hunga Haʻapai volcano in January 2022, for instance, seemed to unfold over just a few minutes. But that impression of brevity can be misleading.

For a volcano to erupt, tectonic plates must first align and magma must form deep within the Earth, rise toward the surface and evolve in underground chambers before any lava is finally released – a process that takes hundreds of thousands to millions of years.

Consequently, the Hunga Tonga–Hunga Haʻapai explosion was only a fleeting moment in a story that began long before humans settled in the Pacific, possibly before humans existed at all.

As scientists, we measure the pace of such processes using the geological timescale – and we want those measurements to be as precise as possible.

A land millions of years in the making

Why is this so important? Consider some major findings from recent studies that utilised the previous New Zealand timescale to determine the ages and rates of key events and processes.

One 2021 study mapped the widespread but largely buried volcanic system of Canterbury, characterising 185 volcanoes that have erupted at various stages over the past 100 million years.

These pulses of volcanism were shown to align with major tectonic events, including the breakup of the supercontinent Gondwana and later changes in tectonic plate motion.

The study showed how volcanic activity in New Zealand has repeatedly been shaped by deep, slow-moving plate-tectonic processes – and how present-day landscapes and seascapes can conceal a dynamic geological past.

Geological elements such as the Canterbury volcanic system are the basic building blocks of our island nation; the composition, arrangement and properties of such
elements determine the distribution of resources and hazards within New Zealand.

Another recent study explored how long-term tectonic processes continue to shape modern earthquake hazards.

Focusing offshore from the eastern North Island, geologists examined how rocks and fluids behave along the boundary where the Pacific Plate is being forced beneath the Australian Plate at the seismically active Hikurangi Subduction Zone.

Their modelling suggests that unusually high underground fluid pressures can strongly influence how earthquakes behave, and that these pressures are driven mainly by tectonic squeezing over the past three million years, rather than simply by the weight of sediments piling up.

In other words, earthquakes in this region are shaped by geological processes that have been building for millions of years.

Measuring the past to understand our future

Deep time is equally important for understanding life on Earth.

Recent discoveries in the fossil record show that, three million years ago, close relatives of modern emperor penguins were living in a subtropical climate in the New Zealand region.

This finding challenges the assumption that these large penguins are forced to live along the icy coasts of Antarctica today by some climatic inevitability, and suggests other factors play a decisive role in shaping where species live.

Such understanding from the fossil record is key to predicting how life and species distributions might change in response to warming climate and disturbances to Earth systems.

In further separate studies, researchers reconstructed 100 million years of geographic history of the largely submerged continent from which our home, New Zealand, emerges.

Their studies show how shifting landmasses, rising and sinking terrain and changing coastlines have shaped the iconic landscapes we see today.

Ultimately, deep time helps explain the origins of New Zealand’s distinctive plants and animals.

It frames how we think about using – and sustainably managing – the resources we depend on. And it underpins our understanding of geological hazards and what we can do to mitigate them.

Taken together, all of these studies show why having an accurate, up-to-date geological timescale matters – and why our actions today will affect the planet and our descendants for hundreds of thousands of years to come.

The post Delving into ‘deep time’: what NZ’s ancient past reveals about its present appeared first on MASSIVE News.

But look more closely and the island is changing. Slopes are becoming boggier. Iconic megaherbs such as Pleurophyllum and Stilbocarpa are retreating.

For years, scientists suspected the culprit was increasing rainfall. Our new research, published in Weather and Climate Dynamics, confirms this – and shows the story goes far beyond one remote UNESCO World Heritage site.

A major – but little observed – climate player

The Southern Ocean plays an enormous role in the global climate system.

It absorbs much of the excess heat trapped by greenhouse gases and a large share of the carbon dioxide emitted by human activity.

Storms in the Southern Ocean also influence weather patterns across Australia, New Zealand and the globe.

Yet it is also one of the least observed places on Earth.

With almost no land masses, only a handful of weather stations, and ubiquitous cloud cover, satellites and simulations struggle to capture what is actually happening there.

That makes Macquarie Island’s climate record from the Bureau of Meteorology and the Australian Antarctic Division exceptionally valuable, providing one of the very few long-term “ground truth” records anywhere in the Southern Ocean.

These high-quality records of the observed daily rainfall and meteorology date back more than 75 years and are commonly used to validate satellite products and numerical simulations.

Rising rainfall

Earlier work has found rainfall at Macquarie Island had risen sharply over recent decades, and ecologists documented waterlogging that harms native vegetation.

But no one has explained how the island’s weather patterns are changing, or directly compared the field observations to our best reconstructions of past weather to assess Southern Ocean climate trends.

To fill this gap, we analysed 45 years (1979–2023) of daily rainfall observations and compared them to a widely used reconstruction of earlier weather, known as the ERA5 reanalysis.

We wanted to understand the meteorology behind the increase in rainfall – that is, whether it was caused by more storms or more intense rainfall during storms. To do this we placed each day in the dataset into one of five synoptic regimes based on pressure, humidity, winds and temperature.

These regimes included low pressure systems, cold-air outbreaks and warm-air advection (the warm air that moves poleward ahead of a cold front).

Storms are producing more rain

Our analysis showed that annual rainfall on Macquarie Island has increased 28% since 1979 – around 260 millimetres per year.

The ERA5 reanalysis, in contrast, shows only an 8% increase — missing most of this change.

The storm track’s gradual move toward Antarctica is well established, and our results show how this larger change is shaping Macquarie Island’s weather today.

Crucially, we found that these changes are not causing the increase in rainfall, as one wet regime (warm air advection) was largely replacing another (low pressure).

Instead, storms now produce more rain when they occur.

Why does this matter beyond one island?

If the rainfall intensification we see at Macquarie Island reflects conditions across the Southern Ocean storm belt – as multiple lines of evidence indicate — the consequences are profound.

A wetter storm track means more fresh water entering the upper ocean. This strengthens the different layers in the oceans and reduces the amount of mixing that occurs. In turn, this alters the strength of ocean currents.

Our estimate suggests that in 2023 this additional precipitation equates to roughly 2,300 gigatonnes of additional freshwater per year across the high-latitude Southern Ocean – an order of magnitude greater than recent Antarctic meltwater contributions. And this difference continues to grow.

More rainfall will also affect the salinity of water on the ocean’s surface, which influences the movement of nutrients and carbon. As a result, this could change the productivity and chemistry of the Southern Ocean – one of the world’s most important carbon sinks – in still-uncertain ways.

This increase in rainfall requires a matching increase in evaporation, which cools the ocean, just like our bodies cool when our sweat evaporates. Over the cloudy Southern Ocean, this evaporation is the primary means of cooling the ocean.

Our analysis indicates the Southern Ocean may be cooling itself by 10–15% more than it did in 1979 – simply through the energy cost of evaporation that fuels the extra rainfall. This evaporation is spread over the broader Southern Ocean.

In effect, the Southern Ocean may be “sweating” more in response to climate change.

The next challenge

Macquarie Island is just one tiny speck of land in Earth’s stormiest ocean.

But its long-term rainfall record suggests the Southern Ocean – the engine room of global heat and carbon uptake – is changing faster and more dramatically than we thought.

The next challenge is to determine how far this signal extends across the storm track, and what it means for the climate system we all depend on.

The authors would like the acknowledge Andrew Prata, Yi Huang, Ariaan Purish and Peter May for their contribution to the research and this article.

The post Storms in the Southern Ocean are producing more rain – and the consequences could be global appeared first on MASSIVE News.

It isn’t alone in this. Antarctica and the sub-Antarctic harbour a large number of endemic species, which means these species are only found in one or a few locations in the world.

In other words, these regions have a high degree of “endemism” – an important metric that tells us where to focus species conservation efforts.

But our new study shows that the degree of endemism in Antarctica and the sub-Antarctic – and in the southern hemisphere more generally – has been underestimated.

This is important because areas with a high degree of endemism harbour species with restricted ranges, unique evolutionary history or unique ecological functions. This makes them potentially more vulnerable to disturbances such as climate change, fundamental changes in habitat, or invasive introduced species.

If the degree of endemism is underestimated, conservation efforts may overlook the sites that are home to irreplaceable birds.

Biased measurements

There are two reasons why global patterns of species endemism aren’t well defined. First, the most common method used to calculate endemism tends to give higher values to places with more species overall – this is known as species richness.

In addition, global studies of diversity often exclude areas that are comparatively species-poor. These areas are mainly in the southern hemisphere – most notably the Antarctic region. When sites that only contain a few species are left out, this influences the estimates of endemism for all other sites.

An alternative way to calculate endemism takes into account a site’s “complementarity”. This metric considers whether species found at a site are also found elsewhere. With this method, we can find sites that have the highest percentage of species with a restricted range.

At such highly endemic sites, the local ecosystem relies heavily on species with restricted ranges to function, which makes them all the more irreplaceable.

Global hotspots for endemic species

This is the approach we used in our new study to reassess the endemism of birds worldwide. In our study, we also considered other aspects of bird diversity. We measured endemism with regard to whether sites hold irreplaceable evolutionary history and ecological functions of birds.

We found that southern-hemisphere communities showed higher rates of local endemism than northern-hemisphere communities across all aspects of diversity. The sub-Antarctic islands and the High Andes, as well as several regions in Australia, Aotearoa New Zealand and southern Africa, stand out as global hotspots of endemism.

These regions hold many charismatic birds with unique evolutionary histories or unique ecological functions, and these birds are largely restricted to the southern hemisphere.

Among these are the palaeognaths – the bird lineage that includes kiwis, emus, cassowaries and ostriches. They also include the lyrebirds and the New Zealand wrens, as well as iconic Antarctic species such as penguins and albatrosses.

Not much land, a lot of ocean

The higher rates of endemism in the southern hemisphere are likely related to the uneven global distribution of landmass. Put simply, there is much more available landmass in the northern hemisphere. As you go further south, landmasses become increasingly separated by vast expanses of ocean.

Because of the smaller and separated landmasses, species in the southern hemisphere have much smaller ranges than species in the northern hemisphere. Consequently, local species communities share fewer species with each other. This leads to the higher observed endemism in the southern hemisphere.

A heightened vulnerability

Our findings suggest that birds in the northern and southern hemisphere might react differently to environmental pressures. Unfortunately, most studies on the impact of climate change to date are from the northern hemisphere.

In response to climate change in particular, species are expected to shift their ranges towards cooler climates. While northern-hemisphere birds are likely free to shift their ranges across large stretches of uninterrupted landmass, birds in the southern hemisphere are hindered by vast expanses of ocean that separate the different landmasses on which they live.

For species at the southern tips of South America, Africa or Australia, the nearest major landmass towards the south is Antarctica. But it is unsuitable for most bird species.

The potentially heightened vulnerability of southern-hemisphere birds suggests they deserve more protection. In addition to known species diversity hotspots that hold large numbers of species, conservation efforts should consider areas that might hold only a small number of species, but irreplaceable ones that aren’t found anywhere else.

The post The southern hemisphere is full of birds found nowhere else on Earth. Their importance has been overlooked appeared first on MASSIVE News.