Freshwater biologist Mike Joy has been in the news recently for claiming New Zealand is not all that clean and green. He’s pointed out that most of our lowland rivers are contaminated with faecal bacteria, our lowland lakes are polluted, and two thirds of our native fish species are threatened with extinction. But Joy repeatedly goes further, claiming New Zealand’s whole environmental record is dubious: “We are now much much closer to the bottom than the top of global comparisons on environmental performance.”
For this, he was slammed in a New Zealand Herald editorial for “exaggerating” New Zealand’s environmental woes. Joy had told the paper, “We are nowhere near the best in the world, we are not even in the top half of countries in the world when it comes to clean and green.” The Herald took issue: “Whatever its deficiencies, it is nonsensical to place this country in the company of the world’s more polluted nations.”
Is New Zealand’s environmental record really well below average? On the web, in print, and in a recent Media3 interview, Joy repeatedly quotes a recent study (Bradshaw, Giam, and Sodhi 2010) published in the open-access journal PLoS ONE, “Evaluating the Relative Environmental Impact of Countries”. The New York Times article that kicked off the latest kerfuffle quotes its most painful finding: out of 179 nations examined, New Zealand was the 18th-worst in its impact on the natural environment.
That’s a pretty terrible grade. But is it accurate? I took a close look at the study, and the report card it compiled on New Zealand, to see if it held up.
What are these rankings?
Bradshaw, Giam, and Sodhi (2010) were attempting to come up with an objective measure of environmental performance for countries so they could test the effects of social factors, like per capita wealth or governmental corruption, on environmental impact. Their goal was to put together a rough working database, not compile league tables for ranking all the world’s nations. But, surprise surprise, that’s how the study is being used in New Zealand.
To come up with a rank, the authors gathered data on seven different variables and took the log-average or geometric mean (not the same as an ordinary average, this stops extremely high or low values from having as big an effect). As long as there were data available for three of the seven variables, a country was ranked in the league tables (179 of the 228 countries examined qualified).
The results summarised countries’ absolute impact on the global environment—all the usual suspects (China, the USA, Brazil, Japan) scored badly, but New Zealand didn’t—as well as their relative ranking, corrected for size. The latter is where NZ appeared in the bottom 20 (Singapore was worst, in case you’re wondering); here’s the rogues’ gallery, from the original paper but with some social and population information edited out.
Edited data from Bradshaw, Giam, and Sodhi (2010), showing the 20-worst environmental baddies, and the seven variables used to rank them—each variable is explained below.
What exactly are these variables?
It’s worth examining the variables one at a time, to understand where the rank of 18th-worst came from. They seem perfectly reasonable at first glance, but the more I poked them, the more dubious I got. New Zealand is ranked out of a maximum of 228 countries, though usually fewer than that as data weren’t available for every country. The lower the number, the worse we are.
Natural Habitat Conversion
NZ rank: 89th
This is the percentage of the land that’s human-modified: urban areas, crops, and managed land. In New Zealand, almost all open land below the tree line should count as human-modified—lowland tussock grassland was created by Polynesian fires and maintained by sheep grazing—so we should probably be ranked worse than this.
NZ rank: 73rd
Marine fisheries take, divided through by coastline to correct for country size. How did the study cope with countries that have no marine fisheries, because they’re completely landlocked? Rather than leave them out of the rankings, they’re awarded a perfect score. Part of the reason the Central African Republic, that paragon of environmental stewardship, got the second-best ranking in the world.
NZ rank: 91st
The ranking used here is based on BOD, a estimate of total dissolved oxygen being consumed by aquatic bacteria, divided through by the total yearly waterflow for each country to keep things proportional. New Zealand no doubt does well because of our abundant rivers and high rainfall. I’m stumped as to why the ranking here bears no relation to the research Mike Joy cites, which found excessively high levels of bacteria, nitrogen, and phosphorus in most of the 300 lowland rivers sampled. It would be remiss, by the way, to not mention the irony of condemning NZ’s environmental record with a study that says our water quality is OK.
Natural Forest Loss
NZ rank: 98th
The authors looked at the change in native forest area between 1990 and 2005; they calculated this from FAO statistics, subtracting plantation forests from the total forest area. New Zealand is about the middle of the pack, because our amount of native forest didn’t change over that time. (I’ve updated the data to 2010.)
|New Zealand (98th)||1990||2000||2005||2010
Wait a minute: according to the FAO stats, our forest area not only didn’t change; it stayed exactly the same, to the hectare. Dodgy data alert! And we know that’s not true: between 1997 and 2002 we lost at least 2000 Ha of native forest, according to satellite imagery; between 1990 and 2008 over 50,000 Ha was deforested, and a similar amount naturally regenerated. So the FAO data look suspicious.
To check it, I picked another couple of countries at random; Samoa, which had an exemplary deforestation ranking of 196, and Korea, with the bad boys at 23.
Notice there’s missing data from 1990; presumably there were actually plantations in Samoa and Korea before 2000. The researchers seemed to have assumed that no data mean no trees, so Korea is unfairly accused of massive forest loss (ranking it among the worst 15% of countries for deforestation). It looks like Samoa though has increased its indigenous forest area by 6.9% since 1990, giving it an overall environmental impact ranking, according to this study, of 173 out of 179. Not bad for a country that had one of the most rapid rates of deforestation in the world in the 1990s. Forest clearance is rampant in Samoa, these numbers are nonsense, and so is Samoa’s ranking. I picked these two countries completely at random—who knows how shonky the rest of the database is? At the very least, the researchers need to go through and recalculate ratings using only available data.
NZ rank: 93rd
Why do we get off so lightly here? Because the only carbon emissions the study counted were fossil fuel usage and clearing land for agriculture. While those are the two biggest components of most countries’ carbon footprints, they’re not ours. Nearly half of our CO2-equivalent emissions are from agriculture and the digestive systems of cows; methane and NO2 aren’t counted by this study at all.
NZ rank: 13th
New Zealand does use an awful lot of fertiliser, but are we really 13th-worst in the world? The problem lies with how the study calculates fertiliser use: total imports divided by area of arable (crop) land. Now, that’s fine for most countries, where fertiliser is applied mostly to crops. But in NZ most of our fertiliser is going onto pasture, and pasture makes up almost all of our agricultural land.
Dividing our fertiliser imports by just our arable land area overestimates the amount we use by a factor of maybe 10 or 20. No wonder we’re 13th-worst!
Proportion of Threatened Species
NZ rank: 1st
At last, a field in which New Zealand can be proud to say we’re number one! The species counted are amphibians, land mammals, and birds, and since all our frogs and bats are threatened, and 70 of our bird species, we do indeed take the title here. This ranking, more than all the others, is the reason we’re near the bottom in the PLoS study. Four things to ponder, though.
- We don’t have threatened species for the reasons most countries do: ongoing deforestation and pollution. Most of our extinction and species decline was happening 100 or 150 years ago, well out of the timeframe of this study. These days, increases in the proportion of threatened species in New Zealand occur because we’re actively studying the genetics of our native animals and discover small isolated populations are actually species.
- Extinction is really the thing we should be measuring, but it’s harder to count, as it’s difficult to know whether a species has vanished or is just very rare. In most countries, the number of endangered species is a good proxy for the extinction rate, but not in New Zealand. We haven’t lost a bird, frog, or bat species since 1972 (Bush Wren), and have pulled several back from the brink—the Black Robin from 11 individuals, the Kakapo from 50). It’s quite possible, thanks the the fine and underfunded work of the Department of Conservation, that none of them are in danger of going extinct in the future (which is more than most countries can claim).
- Why do we have so many threatened species? Because we’re a small island country. Small countries have a greater proportion of endangered species than large ones: the bigger your country, the harder it is to wipe out all of a species living in it. Islands have more threatened species than the mainland: there’s nowhere for native species to escape to, and evolving in island isolation makes animals more vulnerable to extinction. Both these points are not controversial in conservation biology (references coming!), but are tersely dismissed in the PLoS paper. Their evidence: one unpublished study by one of the co-authors that looks at plants not animals. It does seem a bit unfair that New Zealand is penalised for being a small island country, something I don’t think can be laid at the door of either Labour or National governments.
- Why do we have so many threatened species? Because Aotearoa is the last place humans settled: we arrived only 800 years ago. Every other country in the world has already suffered the mass extinction that occurs whenever humans encounter the local wildlife; we’re still working through the tail end of ours. If Europe had only been settled 800 years ago, the French would right now be battling at great expense to save their last endangered lions, leopards, and mastodons. Again, it’s not all that fair to condemn New Zealand for choosing to be settled so late.
So how accurate is our ranking?
Not very. One of the variables dominates all the others, but is a little unfair. One of our rankings is just a blunder. A couple of variables are calculated wrongly, one database looks pretty dodgy, and the whole issue of sustainable fishing when you don’t have a coastline skews all the results. Nevertheless, we can have a go at recalculating the ratings.
|Habitat conversion||89||Depends of definition of “human modified”||60?||Only if other countries are reassessed too.
|Marine capture||73||No coastline = perfect score!||-||Omit from everyone’s rankings until this is sorted.
|Water pollution||93||Doesn’t agree with recent studies||50?||Reconcile the two.
|Natural forest loss||98||FAO data look shonky||98 for now||Database needs to be checked, scores recalculated.
|CO2 Emissions||93||Misses out agriculture||50?||
|Fertiliser use||13||Wrongly calculated||100?||Need data for our fertiliser use on arable land.
|Proportion of threatened species||1||Could correct for insularity, country size||10?||
That rank is still not great, but it puts us in the vicinity of South Africa, the UK, and France. Sure, my recalculation is just handwaving, but it’s definitely more justified than the rank of 18 the PLoS study gave us. Those global rankings are probably OK for testing broad-brush models of the effect of social variables on environmental performance. But the data are so dodgy that I wouldn’t dare use them at all for the purposes of grading a country on an environmental report card.
New Zealand’s environmental impact might well put us in the bottom half of the world league table, but we actually don’t know if it does or not, and this study is not much help. Our country has real environmental issues—and is not by a long shot “100% pure”, absolutely or relatively, despite what the PM says—but claiming we are 18th-worst in the world seems just flat-out incorrect. And if you continue to claim it after knowing how dodgy the data are, you’ve crossed a line from science into advocacy.