UN to adopt S’pore nature ‘report card’ for cities

Dear Mr Mah,

I refer to the 28 Oct 2010 Straits Times report of the United Nations adoption of the Singapore Index on Cities’ Biodiversity.

The purported objective of the Index is to benchmark biodiversity conservation efforts. However, many of the indicators in the Index measure biodiversity, not biodiversity conservation effort. All else being equal, a city located within the tropics would tend to have more biodiversity compared to one located in other climate regions. In other words, the Index favours tropical cities like Singapore over cities found in other climate regions. Therefore, unlike what was purported, the Index is anything but fair.

Indicator 2: Diversity of ecosystems

Counting the number of natural ecosystems in the city doesn’t necessarily reveal the city’s conservation efforts. For example, the land on which the city was built may originally contain 10 ecosystems. Over time, 6 ecosystems were bulldozed to make way for progress. But the city still contains 4 ecosystems and in accordance to the Index, has performed better than another city which has only 1 ecosystem even if that is the only ecosystem the city has ever had from time infinite.

A fairer and more meaningful way would be to compare each city’s current ecosystems against the ecosystems that used to exist, say 100 years ago.

Indicator 3: Fragmentation measures

It is not clear from the user manual whether two plots of nature separated by an expressway but linked at one place is considered one plot or two plots. A tiny nature corridor can’t be compared to a situation where there is absolutely no barrier between the plots whatsoever.

Indicator 4: Native biodiversity in built-up areas

The most important criteria used to gauge the health and maturity of a nature plot is the presence of large mammals, not birds. Some birds are migratory. When you sight them en route to their nesting place, do they count towards native biodiversity?

Indicators 5 to 9: Number of native species of plants (5), birds (6), butterflies (7) and two other living groups (8 and 9)

The number of plant species depends a lot on climate. Singapore may have more plant species than Abu Dhabi. But that’s only because Singapore is located in the tropics whereas Abu Dhabi is located in the deserts, not because Singapore has done more to conserve plants compared to Abu Dhabi. Therefore, this indicator is not only unfair, it doesn’t reveal conservation efforts by either city.

A better way to measure conservation efforts is to compare a city against a nature plot of the same climate type nearby. For example, the number of plant species in Singapore can be compared against the number of plant species found in a virgin jungle plot of the same size in Indonesia. How closely we match up against the virgin jungle would be a measure of how well we have done in respect to the climate type that we have. In the case of Abu Dhabi, the comparison would be an uninhabited desert plot nearby.

Indicator 6 is a duplicate of indicator 4 which over-enhances the role of birds in the Index unnecessarily.

Indicator 12: Cost of cleaning water

This indicator is also unfair because water quality depends on geology. Water obtained from mountain streams tends to be cleaner because it is nearer to the source. Water obtained from rivers that flow through muddy plains tends to be dirtier. Thus, Swiss cities do not have to spend much to clean up water compared to cities that draw water from the lower stretches of rivers which can be heavily laden with silt. In other words, this indicator doesn’t indicate how well cities have protected their water supplies.

Indicator 13: Number of trees

Again, this indicator is unfair because a city located in the tropics can plant many, many trees and the hot and wet climate would be able to support the trees. On the other hand, a city in the desert cannot just plant as many trees without using up a lot of precious water to keep the trees alive.

A better way is to compare the existing number of trees against the number of trees that would have stood had the city been allowed to revert back to its primeval conditions. In the case of Singapore, we ask ourselves how many trees would have stood on the island had we not built a city on it. We then benchmark the number of trees we have now against that number to see how well we have fared. Similarly, Abu Dhabi can compare the number of trees it has now against the number of trees that would have existed two, three hundred years ago.


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