Too small to avoid catastrophic biodiversity meltdown

27 09 2013
Chiew Larn

Chiew Larn Reservoir is surrounded by Khlong Saeng Wildlife Sanctuary and Khao Sok National Park, which together make up part of the largest block of rainforest habitat in southern Thailand (> 3500 km2). Photo: Antony Lynam

One of the perennial and probably most controversial topics in conservation ecology is when is something “too small’. By ‘something’ I mean many things, including population abundance and patch size. We’ve certainly written about the former on many occasions (see here, here, here and here for our work on minimum viable population size), with the associated controversy it elicited.

Now I (sadly) report on the tragedy of the second issue – when is a habitat fragment too small to be of much good to biodiversity?

Published today in the journal Science, Luke Gibson (of No substitute for primary forest fame) and a group of us report disturbing results about the ecological meltdown that has occurred on islands created when the Chiew Larn Reservoir of southern Thailand was flooded nearly 30 years ago by a hydroelectric dam.

As is the case in many parts of the world (e.g., Three Gorges Dam, China), hydroelectric dams can cause major ecological problems merely by flooding vast areas. In the case of Charn Liew, co-author Tony Lynam of Wildlife Conservation Society passed along to me a bit of poignant and emotive history about the local struggle to prevent the disaster.

“As the waters behind the dam were rising in 1987, Seub Nakasathien, the Superintendent of the Khlong Saeng Wildlife Sanctuary, his staff and conservationist friends, mounted an operation to capture and release animals that were caught in the flood waters.

It turned out to be distressing experience for all involved as you can see from the clips here, with the rescuers having only nets and longtail boats, and many animals dying. Ultimately most of the larger mammals disappeared quickly from the islands, leaving just the smaller fauna.

Later Seub moved to Huai Kha Khaeng Wildlife Sanctuary and fought an unsuccessful battle with poachers and loggers, which ended in him taking his own life in despair in 1990. A sad story, and his friend, a famous folk singer called Aed Carabao, wrote a song about Seub, the music of which plays in the video. Read the rest of this entry »

A posthumous citation tribute for Sodhi

6 11 2012

I’m sitting at a friend’s house in Sydney writing this quick entry before jumping on a plane to London. It’s been a busy few days, and will be an even busier next few weeks.

I met with Paul and Anne Ehrlich yesterday (who are visiting Australia) and we finalised the first complete draft of our book – I will keep you posted on that. In London, I will be meeting with the Journal of Animal Ecology crew on Wednesday night (I’m on the editorial board), followed by two very interesting days at the Zoological Society of London‘s Protected Areas Symposium at Regent’s Park. Then I’ll be off to the Universities of Liverpool and York for a quick lecture tour, followed by a very long trip back home. I’m already tired.

In the meantime, I thought I’d share a little bit of news about our dear and recently deceased friend and colleague, Navjot Sodhi. We’ve already written several times our personal tributes (see here, here and here) to this great mind of conservation thinking who disappeared from us far too soon, but this is a little different. Barry Brook, as is his wont to do, came up with a great idea to get Navjot up posthumously on Google Scholar.
Read the rest of this entry »

Tropical protected areas still in trouble

8 10 2012

© P. Harris

There’s nothing like a bit of good, intelligent and respectful debate in science.

After the publication in Nature of our paper on tropical protected areas (Averting biodiversity collapse in tropical forest protected areas), some interesting discussion has ensued regarding some of our assumptions and validations.

As is their wont, Nature declined to publish these comments (and our responses) in the journal itself, but the new commenting feature at allowed the exchange to be published online with the paper. Cognisant that probably few people will read this exchange, Bill Laurance and I decided to reproduce them here in full for your intellectual pleasure. Any further comments? We’d be keen to hear them.

COMMENT #1 (by Hari Sridhar of the Centre for Ecological Sciences at the Indian Institute of Science in Bangalore)

In this paper, Laurance and co-authors have tapped the expert opinions of ‘veteran field biologists and environmental scientists’ to understand the health of protected areas in the tropics worldwide. This is a novel and interesting approach and the dataset they have gathered is very impressive. Given that expert opinion can be subject to all kinds of biases and errors, it is crucial to demonstrate that expert opinion matches empirical reality. While the authors have tried to do this by comparing their results with empirical time-series datasets, I argue that their comparison does not serve the purpose of an independent validation.

Using 59 available time-series datasets from 37 sources (journal papers, books, reports etc.), the authors find a fairly good match between expert opinion and empirical data (in 51/59 cases, expert opinion matched empirically-derived trend). For this comparison to serve as an independent validation, it is crucial that the experts were unaware of the empirical trends at the time of the interviews. However, this is unlikely to be true because, in most cases, the experts themselves were involved in the collection of the time-series datasets (at least 43/59 to my knowledge, from a scan of references in Supplementary Table 1). In other words, the same experts whose opinions were being validated were involved in collection of the data used for validation.

OUR RESPONSE (William F. Laurance, Corey J. A. Bradshaw, Susan G. Laurance)

Sridhar raises a relevant point but one that, on careful examination, does not weaken our validation analysis. Read the rest of this entry »

The seeds of tropical forest destruction

22 01 2012

Bill Laurance asked me to reproduce his latest piece originally published at Yale University‘s Environment 360 website.

We live in an era of unprecedented road and highway expansion — an era in which many of the world’s last tropical wildernesses, from the Amazon to Borneo to the Congo Basin, have been penetrated by roads. This surge in road building is being driven not only by national plans for infrastructure expansion, but by industrial timber, oil, gas, and mineral projects in the tropics.

Few areas are unaffected. Brazil is currently building 7,500 km of new paved highways that crisscross the Amazon basin. Three major new highways are cutting across the towering Andes mountains, providing a direct link for timber and agricultural exports from the Amazon to resource-hungry Pacific Rim nations, such as China. And in the Congo basin, a recent satellite study found a burgeoning network of more than 50,000 km of new logging roads. These are but a small sample of the vast number of new tropical roads, which inevitably open up previously intact tropical forests to a host of extractive and economic activities.

“Roads,” said the eminent ecologist Thomas Lovejoy, “are the seeds of tropical forest destruction.”

Despite their environmental costs, the economic incentives to drive roads into tropical wilderness are strong. Governments view roads as a cost-effective means to promote economic development and access natural No other region can match the tropics for the sheer scale and pace of road expansion. resources. Local communities in remote areas often demand new roads to improve access to markets and medical services. And geopolitically, new roads can be used to help secure resource-rich frontier regions. India, for instance, is currently constructing and upgrading roads to tighten its hold on Arunachal Pradesh state, over which it and China formerly fought a war.

Read the rest of this entry »

Where are they? Finding (and conserving) the biggest fish in the sea

16 11 2011

A post from my PhD student, Ana Sequeira, on her latest paper just out in Diversity and DistributionsOcean-scale prediction of whale shark distribution.

© W Osborn (AIMS)

The ocean is our major source of water, it stabilises our breathable atmosphere and provides many supplies such as medicines (e.g., anti-cancer therapy drugs1) and food. Despite its the importance for human life, many marine species are now at a high risk of extinction owing to human changes to the oceans.

The whale shark (Rhincodon typus, Smith 1828) – an icon of the oceans of a spectacularly huge size and docile character – is just one of those species.

Despite being a fish that many people (mainly in Southeast Asia) are happy to have on their plate, whale sharks are worth millions of dollars every year in the ecotourism industry worldwide. One would then expect that being such a profitable species, their ecology would be well known and thoroughly studied.

The reality is quite different.

Basic information on whale sharks such as the whereabouts of their breeding areas, the average number of offspring per female, or even how many individuals still exist, is not currently known. Moreover, despite the genetic evidence that whale sharks worldwide are connected among different oceans, it is unclear if they move from places where they are protected to places where they are still illegally fished.

Information on distribution and patterns of occurrence in space and time is essential for conservation, and can help to save entire ecosystems if used correctly, for example: to isolate important mating and breeding areas.

To identify the whale shark’s seasonal distribution patterns in the Indian Ocean, to test if records follow a decreasing trend over time, and if occurrence is related to variation in climatic signals, we used multivariate distribution models of seasonal and inter-annual whale shark sightings opportunistically collected over 17 years by the tuna purse-seine fishery. Read the rest of this entry »

Mucking around the edges

8 11 2011

Barry Brook over at beat me to the punch regarding our latest paper, so I better get off my arse and write my take on things.

This post is about a paper we’ve just had accepted and has come out online in Biological Conservation called Strange bedfellows? Techno-fixes to solve the big conservation issues in southern Asia – and it’s likely to piss off a few people, and hopefully motivate others.

We wrote the paper for a special issue of essays dedicated to the memory of our mate and colleague, Navjot Sodhi, who died earlier this year. The issue hasn’t been released yet, but we have managed to get our paper out well before.

Like Navjot, the paper is controversial. Also like Navjot, we hope it challenges a few minds and pushes a few boundaries. We, as conservation biologists, must accept the fact that we have largely failed – biodiversity is still being lost at an alarming rate despite decades and decades of good science, sound evidence-based policy recommendations and even some rescues of species on the ‘brink’. Huge consumption rates, a population of 7 billion humans and counting, carbon emissions exceeding all worst-case scenarios, and greater disparity of wealth distribution have all contributed to this poor performance.

So what else can we do? Read the rest of this entry »

Little left to lose: deforestation history of Australia

6 10 2011

© donkeycart

I don’t usually do this, but I’m going to blog about a paper I’ve just had accepted in the Journal of Plant Ecology that isn’t yet out online. The reason for the early post is that the paper itself won’t appear until 2012 in a special issue of the journal, and I think the information needs to get out there.

First, a little history – In May this year I blogged about a workshop that I attended at Sun Yat-Sen University in Guangzhou, China at the behest of Fangliang He. The workshop (International Symposium for Biodiversity and Theoretical Ecology) was attended by big-wig overseas ecologists and local talent, and was not only informative, but a lot of fun (apart from the slight headache on the way home from a little too much báijiǔ the night before). More importantly, we  lǎo wài (老外) were paired with various students to assist with publications in progress, and I’m happy to say that for me, two of those have already produced fruit (one paper in review, another about to be submitted).

But the real reason for this post was the special issue of papers written by the invitees – I haven’t published in the journal before, and understand that it is a Chinese journal that has gone mainstream internationally now. I’m only happy to contribute to lifting its profile.

Given that I’m not a plant ecologist per se (although I’ve dabbled), I decided to write a review-like paper that I’ve been meaning to put together for some time now examining the state of Australia’s forests and the history of her deforestation and forest degradation. The reason I thought this was needed is that there is no single peer-reviewed resource one can turn to for a concise synopsis of the history of our country’s forest destruction. The stats are out there, but they’re buried in books, government reports and local-scale scientific papers. My hope is that my paper will be used as a general reference point for people wishing to get up to speed with Australia’s deforestation history.

The paper is entitled Little left to lose: deforestation and forest degradation in Australia since European colonisation, and it describes the general trends in forest loss and degradation Australia-wide, followed by state- and territory-level assessments. I’ve also included sections on plantations, biodiversity loss from deforestation and fragmentation, the feedback loop between climate change and deforestation, the history of forest protection legislation, and finally, a discussion of the necessary general policy directions needed for the country’s forests.

I’ve given a few titbits of the stats in a previous post, but let me just summarise some of the salient features here: Read the rest of this entry »


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