While there are many, here are 3 causes of threatened species in New Zealand – habitat loss, predation, and being outcompeted. Aotearoa now has about 4,000 native species listed as threatened or endangered!
As I’ve talked about over and over in this blog, the country of New Zealand is full of truly unique plants and animals that don’t live elsewhere in the world. For nearly 80 million years these islands were isolated from the rest of the world, including from people. Then around 750 years ago when the first people arrived, the country began a period of major changes to the natural environment. People introduced many species, including mammals such as stoats and possums that have had a devastating effect on the native species.
The 3 Main Threats To New Zealand’s Native Species
While there are many reasons that the native species of New Zealand are under threat and at risk of going extinct I want to list off the three main causes or as I think of them, the three horsemen of the apocalypse for native species. All three of these are somewhat related and all are a direct result of people.
These causes are not unique to New Zealand, but are unfortunately repeated throughout the world. There is often a struggle between people making the land a place they can survive and the survival of native species.
Habitat Destruction
The first of the three horsemen is one of the driving forces behind threatened species worldwide – habitat destruction. Simply put, this is changing a natural area into something else. For example, it could be filling in a wetland and converting it to pasture or urban area. Or it could be cutting down forest to allow for planting crops or for grazing animals.
There are around 54 species of native fish in New Zealand, but about 70% of them are now threatened. One of the main causes of this is habitat loss, such as clearing of bush for farmland. Many native species require bush overhanging small streams for shelter and to support their food sources.
Predation by Introduced Species
The second of the three horsemen is that native species are often eaten or killed by introduced species. Remember, New Zealand was an isolated land with no mammalian predators for millions upon millions of years. That means that many native species in New Zealand evolved without developing the natural defences that species that co-evolved with predators have. Thus, when people introduced rats, possums, and mustelids (stoats, ferrets, and weasels), the native species were easy prey for them.
Not only were the native species easy prey for them, but they were easy prey for people as well. The native moa were wiped out in a relatively short time by early hunters. Introduced stoats have led to the extinction of the bush wren, laughing owl, and New Zealand thrush. Additionally, stoats are a serious threat to many other native birds, including juvenile kiwi, whio, and takahe.
Outcompeted by Introduced Species
The final of the three horseman is that native species are simply outcompeted by introduced species. For example, an introduced species, such as a plague skink is able to outcompete the native skinks. Despite a smaller size, the plague skink reproduces much faster than the native species. This allows the introduced plague skink to expand its population much faster than the native species populations. Over time, this would lead to the larger population of introduced skinks outcompeting the native skinks for resources.
The introduced plague skink can now be found over much of the North Island.