中国式灾害经济学

最近天灾不少，从新闻网站的首页就能看出来：

Google 新闻截图--数一下有多少条救灾报道

值得注意的是“十六勇士冒死爆破堰塞湖”“各地献爱心支援甘肃舟曲灾区度难关”“中国19省区将遭大到暴雨猛烈袭击，多地暴雨成灾”这几条新闻。它们反映了我国长期以来应对自然灾害的模式─在灾害发生以后，立即投入国家应对突发事件的传统力量，同时动员社会各界提供物资、财力的支援，这种模式反应不可谓不及时，措施不可谓不有效，但是同时，不那么惨烈，也不那么吸引眼球的自然灾害可能正在更大的尺度上发生，而现有的模式只能跟在正在发生的灾难后面，无法减少未来灾害发生的可能性。

从另一个角度看这件事，当然也很容易理解。任何官员都愿意通过救灾来说明自己的能力，积累自己的政绩。至于说减灾，就不那么容易体现出自己到底做了哪些工作。因为没有问题的时候，我们倾向于忘记问题曾经存在和为解决问题付出的努力。更何况你在任上减了灾，让下一任做什么？这种损人不利己的事多数有头脑的官员都是不会干的。

这种想法反映到应对灾害的态度上，就是宁可年复一年花钱救灾，也不愿花小得多的一笔钱防灾减灾。刚刚过去不久的云南大旱，造成数十万人饮水困难和上百万人因旱缺粮，但旱灾来了又走，却没有看到当地政府有任何防御未来旱情的动作，尽管近几年冬季降水都偏少，而且A有预测称最近几年仍然会有大旱，这次旱灾过后增加的少量小水利工程还都没有政府投资的影子，往往都是当地居民出于自救考虑的临时工程。一次次地救灾，GDP 是涨上去了，民生却越来越成问题。

这种救灾经济在我国的话语体系下对于普通人还有更加微妙的影响。从数字上看，国家对救灾和重建的投入确实远大于民间力量的捐助。但这部分投入作为对地方的投资，国家是有很大把握通过税收等形式再收回的，而投资实际上对居民收入的提高和能力的建设有什么样的作用还要看用途。玉树地震以后，青海省提出的重建战略是把玉树建设成旅游城市，但是旅游这种极为依赖投资的经济，对改善大部分人的生活未必有好处。汶川的重建战略则要完整周全得多，其关于避免未来类似灾害的规划堪称范本，但其它曝光度低的灾区就不一定能被这么周全地加以考虑了。无论采取哪种重建的策略，这种年年有灾害，年年要捐款的灾害经济模式对于民间力量都会构成不小的负担，这部分人的“投资”是没有回报而且无休无止的。而同时，捐款人仍然要一分不少地交税，久而久之，这也构成了另一种国进民退，在一次次自然灾害中，个人陷入负向的帕累托改进，而国家则可以积累越来越多的财富。

Update: 今天看到网上表达类似观点的帖子，提到给汶川地震的捐款总额应该是760亿，而且这一点似乎得到了官方媒体的证实，我原先以为捐款只有50多亿元，现在把这760亿或者进入政府财政帐户的600多亿捐款跟国家投入的200多亿比较，汶川重建显然是一场彻头彻尾的国进民退运动，而规模较小但性质相同的运动可能每年都会上演。

A modular tool for vulnerability study

The DIVA (Dynamic and Interactive Vulnerability Assessment) tool is a modular "discussion-making" tool developed by the EU funded [DINAS-COAST](http://www.dinas-coast.net/) project. The tool is used to facilitate the assessment of vulnerability in coastal areas. It tries to address these drawbacks of similar tools and models:

* Low resolution and obsolete data sources;
* Limited number of scenarios;
* Unable to identify causes of vulnerability except for sea-level rise;
* Not considering social-nature interaction and feedback;
* arbitrary and simplistic assumptions about adaptation.

The main characters of the DIVA tool are:

* Integration of multiple disciplines in the study and simulation of vulnerability issues;
* Modular architecture allows constant update and evolution of the tool, to adapt to changing contexts and adaptation/succession;
* Non-expert friendly interface, designed to help answer questions asked by stakeholder and researchers from a wide range of groups.

Using a relational geospatial information database as its foundation, the DIVA tool can be considered as a set of modules, each addressing a process contributing to the vulnerability of coasts, governed by a framework that describes the conceptualization of the system in question. Only processes that conform to the general conceptualization can be modelled.

The development of the tool is an interesting case study of distributed software engineering. The authors of the modules belong to different institutions all over the Eurasia continent, and collaboration has to be carried out with email, Internet and phone. During development, the developers cannot even tell what the interfaces of the modules would be. To coordinate the efforts, the whole consortium used an ontology (conceptualization) of the system, and stored it as XML in a central location. The ontology then guides developers to establish algorithms and data structures. The module then goes to a stand-alone mode test. Finally, the linkage of the module with others and the whole model are tested.

Judging from the difficulties of developing such a complicated project, the DIVA tool is an exceptional success. However, the modular approach also have its own problems. The most significant one is that one module's underlying theory and implementation are often not concerned by other experts, and the relationships between modules are not always well understood. This perhaps is why the author of [the article](http://dx.doi.org/10.1016/j.gloenvcha.2009.03.002) calls the DIVA tool "transdisciplinary" instead of "interdisciplinary".

An important issue in vulnerability studies is [the cross-scale interactions](http://dx.doi.org/10.1191/030913200701540465). The DIVA tool cannot address this issue well, but the authors are pretty sure that the modular structure of the tool allows these features to be easily added. It is natural to consider the possibility to expand the tool to other vulnerability problems, such as desertification or energy dependency, but this may need a new framework. It is also not clear whether the DIVA framework supports modelling of long-range interactions.

The authors do not expect the DIVA tool to answer all vulnerability questions. They call it a "discussion-making" tool instead of a "decision-making" tool. The ability to better incorporate stakeholders in vulnerability study is eagerly needed in all kinds of socio-ecological systems. It would be wonderful to see more DIVA-style tools appear.

Hinkel, J., & Klein, R. (2009). Integrating knowledge to assess coastal vulnerability to sea-level rise: The development of the DIVA tool Global Environmental Change, 19 (3), 384-395 DOI: 10.1016/j.gloenvcha.2009.03.002

Adger, W. (2000). Social and ecological resilience: are they related? Progress in Human Geography, 24 (3), 347-364 DOI: 10.1191/030913200701540465

What is truly adaptive management?

Folke et al. (2002) argued that active adaptive management can help resilience-building in social-ecological systems. Active adaptive management, by their definition, considers policy as a set of experiments designed to reveal underlying processes that build or maintain resilience. They pointed out that to achieve active adaptive management the managing institution should be open and flexible governance bodies that can "learn, generate knowledge and cope with change".

In real life scenarios, the problem with active adaptive management is what should the decision makers and stakeholders learn from the experiments and what kind of institution is really "adaptive".

[A new article](http://dx.doi.org/10.1016/j.gloenvcha.2009.06.001) appearing in Global Environmental Change is another attempt to tackle these questions. The author argues that often policies are not adaptive in that they are just trying to adjust actions according to the effect, without further questioning the underlying constraints and contexts of the action. To be adaptive and help build resilience, the governing regime should adopt multiple levels of learning, starting from refinement of actions, to questioning the frame of reference and underlying assumptions, to transform the structure of context and established values and norms. If the institution is only limited to the first loop of learning, it may finally encounter some restraints that limit its adaptive capacity. As a result, in the face of larger environmental or socioeconomic changes the institution will fail to maintain the resilience of the complex system.

The author further points out that a government-dominated institution would not be flexible enough to adopt the second- or third-loop learning, which requires the change of the whole actor network, regulations and the structure of the institution. As a complement of the "formal" institution, the "informal" institution featuring stakeholder participation, more flexible regulation, and local knowledge should be introduced. It is noted that such kind of informal institutions often lack a voice or ability to take actions in large-scale projects, thus a hybrid institution combining the executive power of formal institutions and the flexibility of informal institutions is called for.

The trend of more active informal network, or "shadow network", may see the hierarchy in environmental management more diminished. How to guarantee the voice of the informal institutions heard may not be a major problem in industrialised countries, but will be one for minority groups and marginalised communities in developing countries. To establish a context around their point of view will be an interdisciplinary challenge.

Claudia Pahl-Wostl (2009). A conceptual framework for analysing adaptive capacity and multi-level learning processes in resource governance regimes Global Environmental Change, 19 (3), 354-365

Carl Folke, Steve Carpenter, Thomas Elmqvist, Lance Gunderson, C S Holling, & Brian Walker (2002). Resilience and Sustainable Development: Building Adaptive Capacity in a World of Transformations Ambio, 31 (5), 437-440

在模型中虚拟理性人

在生态系统模型中加入对社会经济层面的模拟是个难题。一般来说，这种模拟要建立在实地调查的基础上，否则很难定量。今天的 Ecological Modelling 上发表的[一篇文章](http://www.sciencedirect.com/science/article/B6VBS-4V9252X-2/2/5ddd2302b7b6a56c7ef7d34b6839fc7b)绕过了这个问题。作者用经济中的效用（Utility）作为经济系统模拟的目标变量，并假设系统中的人追求效用的优化，以此为出发点讨论经济系统对自然生产力的影响。

《Collapse》：为明天而改变

对于一个从[《枪炮、病菌与钢铁》](http://www.douban.com/subject/1054760/)之后第二次接触 Jared Diamond 作品的人来说，对这本书的论点持一定的怀疑态度是有必要的。这本书的写作风格与《枪炮》如出一辙，而且也一样成为了叫好又叫座的畅销书。这不免让人怀疑Diamond 与 Leslie Brown 或 Lomberg 一样都是以研究为名拼凑所谓证据，炮制一本又一本畅销书的主儿。对我来说，这种怀疑在阅读的过程中虽然没有完全减退，但 Diamond 继《枪炮》之后又一次以他旁征博引的写作风格和流畅大气的文字打动了我，使得我相信他不太可能为了说服读者而有意扭曲引用的证据，更不可能仅仅为了写一本畅销书而抛出一个看似惊世骇俗的论点再勉为其难地用片面的论证来“证明”。Diamond 写书的意图，据他自己说，是在惊讶于玛雅和复活节岛文明的神奇之余，想到了为什么这些古老的社会最后不免于崩溃的命运。写作这本书，也是为了让读者能够以史为鉴。从这个目的出发， Diamond 再次使用了传统史学家的写作方法，试图通过对历史案例的分析，归纳出以往社会走上崩溃或繁荣道路背后的文化、体制、政治和经济原因，并讨论现代社会面对的不同挑战及如何避免崩溃。和《枪炮》一样，这本书的大部份章节分别讨论了不同的案例，每个章节中案例的叙述与分析既有机地紧密结合，又泾渭分明；描述的部分文笔流畅生动令人不忍释卷，论证的部分即使不是无懈可击，也做到了详尽周密，对于这个领域的研究没有超过 Diamond 本人的人，是很难辩驳的。这本书不是严肃的学术著作，但作为科普读物，在有力地传达了大量信息的同时又没有丧失可读性，可谓难能可贵。

全书的中心问题，是人类社会如何及为什么选择了通向最终崩溃或长期繁荣的道路。这个问题的变体，是为什么某些社会即使明知自己选择的道路是不可持续的，还是头也不回地沿着这条道路走下去？Diamond 在书中对这两个问题都从他的角度进行了充分的讨论。他将古往今来社会崩溃的原因归纳为五大因素：

1. 环境的破坏；
2. 气候变化；
3. 来自毗邻社会的敌意和威胁；
4. 缺少或失去友好邻邦的支持；
5. 社会对面临问题的反应。

其中第二点，对于古代社会而言并非人类造成的气候变化，所以人类并没有多少选择权，而一个社会对于其邻邦的选择自由也有限，因此纵观全书，不难看出 Diamond 还是给了环境问题和社会的适应这两个议题最多的关注。在环境问题的讨论中，作者几乎每次都必会谈到人口问题。在诸如复活节岛和玛雅这样的社会，不受限制的人口增长与气候变化的相互作用造成了环境与发展的[尺蠖效应](http://www.snakehsu.info/wordpress/?p=458)：在气候适宜的时期，社会的发展以环境的承载能力为代价；而气候变得恶劣时，社会的损失又是以社会资本（经济和机构）的破坏来弥补。如此反复的拉锯是这些社会走向崩溃的一个重要因素。那么这些社会为什么没有在第一次面对恶劣环境时就改变它们的发展模式？Diamond 归纳了如下几点原因：首先是社会和环境资本的变化极度缓慢，有时超出了人类的认知可以感受的范围；其次即使社会感受到了负面因素的影响，占统治地位的精英（或特权）阶层可能并未直接受到影响，因此也缺乏带领社会走出困境的动机；最后，社会可能极度良好地适应了某种环境或文化认同，以至于在改变到来时没有人愿意放弃已经不合时宜的某些核心价值观。

如果说展示一个社会面对的问题，并呼吁人们采取行动，并不是什么有新意的题材，那么或许可以说《Collapse》将这个题材以一种更具鼓动性，更令人不安的方式上升到了一个新的高度。Toynbee 的[《历史研究》](http://www.douban.com/subject/1052983/)提出了挑战与应战这个范式，用它来解释过社会的崩溃，Diamond 则在继承 Toynbee 的衣钵之余，将这个范式深化，提出了为什么有些社会直接放弃了应战这个问题。而这个巨大的问号，在被 Diamond 联系到当今美国和世界的现实之时，就带来了值得更深入思考的问题：高度成功的工业文明是否也削弱了社会适应变化的能力？当今的精英领导阶层是否有足够的魄力带领社会放弃某些威胁社会存续的核心价值观来保证社会的生存？诚如 resilience 理论（[http://www.resalliance.org/](http://www.resalliance.org/)）所注意到的，在一个系统度过迅猛发展的 r 阶段后，随之而来的 K 阶段保证了前一阶段的物质成果在不断的变化中被保留下来，但代价是系统在变化中维持其关键功能的能力（resilience）不断被削弱，系统也越来越难以适应新的变化。在随后的 $$\Omega$$ 阶段，系统将崩溃，释放 resilience，供下一阶段的重组和发展使用。

世界是否正处于这个 K 阶段？Diamond 并未明确断言。但他在《Collapse》的最后一章中指出，许多社会的崩溃都是发生在其鼎盛时期后一二十年，因此他呼吁在今天的发展中应当更加注重长期的规划，并重新考虑被社会作为核心价值的一些理念的重要性。理想化地说，我以为最后一章可以作为领导人必看的一份 Executive Summary，Diamond 在其中列举了威胁社会生存的十二大问题，也有力地反驳了“照常营业”派决策者和人类（技术）中心主义者在讨论环境、资源问题时经常使用的一些观点。特别重要的是，他指出在当代也有社会由于与古代社会相同的原因，正在发生崩溃或处于崩溃边缘。与古代相比，现代社会大大增加的人口与全球化，使得全球性的崩溃成为可能。正如复活节岛是太平洋中的一个孤岛一样，地球也是太阳系中的孤岛，一旦它发生崩溃，我们无路可逃。

遗憾的是，并不是每一个领导人都会读这本书，在读过后能把长期规划的理念进行实践的可能更少。而且 Diamond 作为正面例子的一些社会，从其全球生态足迹和不可再生资源的消耗来看，也未必就是可持续性的样本。但如果这本书的众多非精英读者们能够思考一下他们的核心价值观，并愿意为社会的存续做一些必要的改变，也许真的能为社会的发展带来新的面貌。因此，我向每一个人力荐此书。

维京人在格陵兰的覆灭与两种适应

[caption id="" align="alignnone" width="130" caption="Book cover via Amazon"][/caption]

昨天爱丁堡大学的 Andrew Dugmore 教授到本校来做了一个讲座，主题是讨论格陵兰岛的维京人的 resilience 和 adaptation。因为和我做的课题有关，而且这几天我在看 Jared Diamond 的 Collapse 这本书，正好也看到关于格陵兰岛维京人的章节，所以对这个讲座很感兴趣。而且这好像还是我在英国第一次看到做 resilience 这方面研究的教授，以前看文献的时候总以为这个东西只有美国和澳大利亚的一小撮人在研究，现在知道离自己相对较近的地方也有人做这个还是挺高兴的。

Andrew 一上来还是从 panarchy 的概念入手，着重介绍了其中的跨尺度（inter-scale）作用，包括大尺度的慢过程对小尺度的快过程的影响（remember），以及小尺度过程的反作用（revolt），事实上维京人与格陵兰岛环境的互动也可以用这两种作用概括。Andrew 与 Jared Diamond 似乎有过接触，他也提到了 Collapse 这本书里对维京人的描述。Andrew 和 Jared 都注意到，一个不可忽视的事实是维京人的环境管理与我们想象的不同，虽然他们一开始对冰岛和格陵兰岛的树木都进行了破坏性的砍伐，但他们都很快意识到树木对草地和他们赖以生存的畜牧业的重要性，并停止了砍伐，并通过调整畜群结构建立起了基本可持续的畜牧业（冰岛可以认为是半可持续地发展了上千年，目前是欧洲生活水平最高的国家之一），但为什么格陵兰岛的维京人没有取得像在冰岛那样的成功，并最终消失了？

一个重要的原因是格陵兰岛的气候比冰岛的更寒冷，但 Andrew 指出，事实上维京人一直适应得很好，建立了完善的社区，并且许多牧场一直保持了良好的状态。他们几乎做对了每一件事情，但无法预见到公元1400年左右的小冰期的出现。气候和植被模型显示在小冰期植被的生长季变短，使得秋季可用的牧场面积局限于较低海拔的区域，而已有的牲畜数量在有限的草场上造成了破坏，而从破坏发生到变得可见再到采取措施都需要相当长的时间，维京人一度适应得非常好的畜牧和狩猎生产方式没有能适应这个突然的变化，其发达的畜群不能在短时间内减小规模，因为适应于畜牧的维京人找不到替代的生产方式，结果导致了其社会在十三世纪初的崩溃。

[caption id="" align="alignright" width="240" caption="The "East Settlement" of Vikings in Greenland"][/caption]

这个理论的警示意义是明显的。和维京人一样，今天的我们也没有对于未来可能发生的突然变化的知识。当变化发生时，我们对已有条件的极度发达的适应可能反而让我们在变化面前无所适从。一个简单的例子是粮食生产，当粮食剩余实际上依赖于大量的能源和化工产品投入的时候，如果生产必需的资料突然出现极度的短缺或者失效，就可能造成严重的影响。而且这种突然的变化出现的可能性，并不因为我们今天的社会比维京人更发达而减小。

在维京人覆灭的同时，因纽特人在格陵兰岛上取得了成功，以至于十六世纪重返格陵兰的欧洲探险者以为因纽特人是格陵兰岛唯一的原住民。Andrew 对于因纽特人的成功的解释是，不同于定居的，农业文化的维京人，因纽特人适应了游猎式的生活方式，他们的流动性（mobility）使得他们能够接触更广阔多样的环境，从而在变化面前有更强的适应能力。活动范围大，意味着因纽特人有更多的选择，这也使得他们的社会更加 resilient。

从这里我想到，当我们讨论社会和人群的适应时，我们说的 adaptation 有两层含义，其一是对现有环境的适应，这种适应是小尺度过程对大尺度过程的 remember 作用的反应，用 adaptive cycle 来解释的话，对应其 r 阶段和 K 阶段；其二是对变化本身的适应，即变化发生时能否及时调整为另一种模式，同时保持系统的关键功能的存在，对应 adaptive cycle 的 $$\Omega$$ 和 $$\alpha$$ 阶段。理想化地说，第一种适应不应当以第二种适应为代价，在改善对某种特定环境的适应的同时，我们也应当维持适应另一种或多种完全不同的条件的可能性，或者至少延缓这种可能性的消失。

不能否认的是我们仍然像维京人一样没有意识到这个问题，我们的生活方式的进步往往导致了适应变化的可能性的丧失，这体现在物种的消失和对个别资源的过度依赖上。至于对第二种适应非常必要的 mobility，在人口日益增长的今天似乎也越来越难保证。虽然在全球化的今天个人可以越来越容易地迁移，但人类还是一种不喜欢陌生环境的动物，结果全球化只带来了趋同的城市和中国城韩国街意大利区这样的聚落的存在，都不利于人类适应变化的环境。维护文化的多样性，同时鼓励与外来人群的交流，以及维护自然环境的多样性，对于人类的第二种适应，我认为将同等重要。

听完 Andrew 的讲座后我又赶场去听了 Tindall Centre 的 Mike Hulme 的讲座，关于“Why we don't agree on climate change”。与他人不同的是他不讨论气候变化的原因或者解决方法或者争议，而是探询为什么存在争议。他指出这是一个文化和思维方式的问题，四种思维范式─怀旧、恐惧、改变自然的骄傲和对社会正义的诉求导致了目前关于气候变化的复杂叙事的出现。也许“我不同意”确实是人类的天性，这也许也能解释为什么人类在突然的变化面前总是要一段时间才能采取行动吧……但这正是让我们成为人类的重要的特质，我们也许不应该为了更好的适应而抛弃它。

Progress

Recently I have managed to derive a dynamic model for my research area, imitating a model proposed by Ludwig et al. (2002) [3.   D. Ludwig, B. H. Walker, and C. S. Holling. Resilience and the Behavior of Large-Scale Systems, chapter 2 Models and metaphors of sustainability, stability, and resilience. Island Press, Washington, D.C., 2002] for a rangeland.  Now I find that it is producing a range of interesting results.  More importantly, I think I can defy accusation that the model is manipulated to produce domains of attractions.  The hysteric behaviour and the appearance of domains of attraction/resilience are emerging from classic dynamic model functions, this is what I call fascinating.

The next step would be setting a range of scenarios, with different sets of parameters, see the behaviour and resilience of the system in these settings.

Furthermore, combining it with what I derived from remote sensing images collected for the last few decades, the model can go spatial to some extent.  Use the remote sensing image to determine the initial state for each pixel, run the model on them, with a specified parameter set for each type of pixels, the result may be very interesting.  Of course the computation would also be intense.  I need also to think about a) how do I verify the model and b) how do I parametrise the different situations for different pixels.

生态/环境研究的新挑战

Holling (1973)[1. Holling, C. S. Resilience and stability of ecological systems. Annual Review of Ecology and Systematics, 4:1–23, 1973.] 这样定义生态系统的 resilience：系统在发生重构和功能变化之前能够接受的最大扰动。而 Pimm (1984)[2. Pimm, S. L. The complexity and stability of ecosystems. Nature, 307:321–326, 1984. ] 在十年之后才提出 resilience 的另一个定义：系统受到扰动后回到初始状态所需的时间。虽然 Pimm 的定义提出较晚，但却得到了广泛得多的应用。而对于 Holling 的定义，虽然研究者往往会提及，却很少有人将其应用到实际研究中，以致到现在这个概念的研究者和实践者似乎已经成了一个不为人注意的学派。为什么 Holling 的想法应者如此寥寥？

Resilience and the Behavior of Large-Scale Systems（以下 RBLSS）这本书可以看作是这个久被忽视的学派争取学界注意的又一次努力，书中文章的主要作者包括 L. H. Gunderson，C. S. Holling，G. D. Peterson，B. H. Walker，S. R. Carpenter 和 D. Ludwig 等人，事实上他们就是仅有的几位我们通过一般的期刊搜索能比较容易地找到的，主张利用 Holling 的 resilience 定义研究社会-生态复合系统的学者。在书中他们重申了自己的想法，即 Pimm 的 resilience 的前提是不成立的，复杂系统并没有一个唯一、恒定、稳固的均衡（equilibrium）状态，相反系统可能有多个均衡状态，外力可以导致系统在这些状态间转换。在一个均衡状态附近（称为均衡域或吸引域），系统的变化是连续而接近线性的，可以用方程描述，但一旦变化超过了一定范围，系统的转变就是突然、非线性的。定义或者评价一个系统的 resilience，就是要找出均衡域的范围和其它可能的均衡状态。

这样的说法比较抽象，所以 Holling 的追随者们使用盆中的小球这个概念来说明：小球相当于系统，放在一个盆（均衡域）当中，盆的宽度就是 resilience 的强弱程度，而小球一旦越出盆沿，就会落入另一个盆，即一个性质、结构、功能都可能完全不同的系统状态。在数学上，他们则利用二分点这个概念来说明系统是如何离开均衡域的：类似我们熟悉的量变引起质变的思想，系统某些变量的取值会使类似下面方程的性质在这个取值附近发生巨大的改变：

$$\frac{dx}{dt} = -x(x^{2} - \alpha)$$

这类变量称为系统中的“慢变量”，变化往往较慢，却对系统的性质和功能有根本性的影响。到这里我们已经可以看到 Holling 的定义固然比 Pimm 的定义更能把握生态系统的非均衡本质，同时也避免了过度的还原论思想，但其实践比起 Pimm 的仅仅通过经验性的观察就可以测量的方法要困难许多，要求研究者对于系统的全面性质和各种内外影响因素都有较全面的了解，这在大的生态和社会经济系统中是难以做到的，难怪许多人望而却步。

也许正是因为这一点，RBLSS 这本脱胎于 workshop 的书将重点放在对大型系统的具体案例研究上。其研究的系统包括了主要的陆地生态系统如森林、湿地和草原，以及水生生态系统如湖泊和珊瑚礁群，研究方法也是多种多样，包括情境分析，数学建模，实地观测和地理信息科学等等。这些案例确实体现了 resilience 这个概念的普适性，但也暴露了它的一个重大不足，就是对于不同的生态系统缺乏一个一致的方法体系。即使在同类的生态系统中，由于物种和扰动因素的不同，研究者也往往不能套用书中给出的分析结果，而要自己从概念模型开始分析。在整个体系中缺乏“可重用”的部分，无疑也限制了这一概念像环境影响评价那样成为工业和学界中通行的做法。

当然，仅从框架来说，这本书也提供了一个可供套用的模式，包括概念模型的建立，跨比例过程和慢变量的识别等等，可供有意利用这个概念进行研究的人参考。但我认为这本书更大的意义在于指出了一条有可能让生态学研究从目前的还原主义研究方法飞跃到真正综合性的，把“人”这一因素纳入研究范围的研究的途径，向传统的研究方法提出了挑战。同时，相对于基于 Pimm 概念的，以某一特定状态为目标、要求保持和固守的环境管理，Holling 的 resilience 概念使得他能够提出新的生态/环境管理思想，即适应性的管理，承认生态和社会系统的变化和非均衡性，这比 resilience 这个概念本身有更大的实践意义，已经在一些具体的环境管理方案中得到应用。在 resilience 的评估当中，又要求研究者对现有的生态模型进行检验，并研究和归纳具体生态系统当中的各种主体和相互作用，这在一定程度上也促进了传统生态学理论和方法论的发展。从这个意义上说，这本书和 resilience 概念本身，对于生态和环境科学的研究者来说具有超越直接价值的意义。

Emergence, or merely a mistake?

When I conduct DFA on my NDVI data, I found some interesting behaviour of the result.  Apparently the system behaves differently in different spatial scales, which is reflected in the fluctuation-temporal scale correlation and the slope of $$\text{log}F(L)/\text{log}L$$ (i.e. $$\alpha$$).

The DFA result for the whole map is like the picture below, $$\alpha$$ is between 0.5 and 1, indicating a correlation between fluctuation and time.  But the pixel results are seemingly random (this is expected), and all have $$\alpha << 0.5$$ (this is quite unexpected), indicating anti-correlations.

After examined the scripts and data in question I believe the design of the experiment has no fault that I could find.  I have also considered the possibility that nonstationarity and trend may have effects on the result, but the NDVI data I used have already had seasonal trend eliminated, while nonstationarity is not likely to cause such dramatic change in $$\alpha$$.  The result, if not a technical failure, will suggest that the system's behaviour at 8km (single pixel) and regional scales are different.  At the fine-grained scale, the fluctuation reduces as temporal scale increases, i.e. a fluctuation is likely to cause smaller and smaller fluctuations in the distant future.  But at coarser scale the behaviour is inversed, a fluctuation may cause larger and larger fluctuations at long intervals.

It is possible that the system's behaviour at coarser scales is the result of relatively simpler interactions at finer scales, creating a phenomenon known as emergence.  But the question is, if it is really emergence, what is the critical scale that such behaviour shift takes place.  Besides, what I have now is at best correlation, are there any intrinsic mechanism that determine such emergence?  In ecology, has there been similar emergence taking place in the shift from community to biome scale?

The system I'm studying is a pastoral socio-ecosystem.  If there is really emergence like this, does it suggest that the system at the farm scale is resilient but as a whole is not [1. There are some resilience researchers noted the problem of emergence, such as

Allen, C.R., Gunderson, L. & Johnson, A.R., 2005. The Use of Discontinuities and Functional Groups to Assess Relative Resilience in Complex Systems. Ecosystems, 8(8), 958-966. and

Folke, C., 2006. Resilience: The emergence of a perspective for social-ecological systems analyses. Global Environmental Change, 16(3), 253-267.]?  This is a really intriguing question.  I just hope it is not raised from a false observation.

Find underlying fluctuation using DFA

We often have to deal with NDVI time series like this.  What does it tell on earth?  Very little information can be identified from this figure and its subsets.  However, techniques like DFA allow us to dig some information on the fluctuation and its cause.

Detrended Fluctuation Analysis (DFA) was first used in DNA analysis to identify whether the purine and pyrimidine base's distubution is scalable, or fractal.  Later it has been used by many to examine whether a bounded time series has fractal characteristics and is self-similar.  First of all the time series has to be converted to a random walk series using equation:

$$X_{t} = \sum_{i=1}^{t}(x_{i}-\langle x_{i} \rangle)$$

Where $$\langle x_{i} \rangle$$ is a value within the range of the time series, or a variable that changes with the element in the time series according to certain rule.  This is the "detrending" step.  Once the series has been converted, one can split the whole series into a number of non-overlapping "windows", each with a equal number of samples or length $$n$$.

Least Square fit is done to each of the windows to get the local trend.  The root-mean-squared deviation from the trend is called fluctuation:

$$F(L) = \[\frac{1}{L}\sum_{i=1}^{L}(X_{i} - ai -b)^{2}\]^{\frac{1}{2}}$$

For different window size $$L$$ we can obtain different $$F(L)$$.  On a log$$F(L)$$ vs. log$$L$$ plot, we have a straight line whose slope is $$\alpha$$ if the random walk has self-affinity.  The values of $$\alpha$$ have different meanings.  $$\frac{1}{2} < \alpha < 1$$ indicates that the fluctuation is correlated with time; while $$\alpha$$ close to 0.5 indicates white noise [1. Detrended fluctuation analysis. (2007, October 31). In Wikipedia, The Free Encyclopedia. Retrieved 13:15, August 1, 2008, from http://en.wikipedia.org/w/index.php?title=Detrended_fluctuation_analysis&oldid=168313780].

This technique is further used to identify whether there is identifiable trend in the variation of NDVI throughout years.  Telesca et al. (2005)[2. Luciano Telesca, Rosa Lasaponara, Antonio Lanorte, 1/f* fluctuations in the time dynamics of Mediterranean forest ecosystems by using normalized difference vegetation index satellite data, Physica A: Statistical Mechanics and its Applications, Volume 361, Issue 2, 1 March 2006, Pages 699-706.] has utilised the technique and identified positive feedbacks and reduced adaptability in Italian forest ecosystem.  Note that NDVI has natural periodic fluctuation due to seasonality, before DFA is applied, one should first reduce this fluctuation from the data.

This technique may also be applied in my study as I am also looking at NDVI trends.  Some spatial analysis may be added by using the technique on single pixels and/or "windows".

Loss of water system resilience

ScienceDaily has a story on possible "ecosystem flipping" in water systems. Traditionally water management focused on "blue water", which includes water bodies that are easy to perceive, such as rivers and lakes. It is argued that water managers have long ignored "green water", whose cycles are not readily observable yet are essential for the function of ecosystems. It is pointed out that

Modern agriculture and land-use practices may lead to major disruptions of the world's water flows, with potentially sudden and dire consequences for regions least able to cope with them[...]

Soil nutrient as a slow variable is being changed due to agriculture practices, and that may cause a sudden ecosystem flip when it reaches a threshold. Yet it is difficult to tell where the threshold is. The original article claims that the most vulnerable area may be poor dryland areas. Using the "ball in the bowl" analogy, one can say that the domain of attraction for the current system is small and shallow. Modern agriculture may have contributed to the situation. But would it be better if the old way of planting crops remains? Would it jeopardise other aspects of the system? The adoption of modern agriculture can be seen as a necessary step to take when the system transits from r to K phase in the adaptive cycle. The task now is to prevent the system from collapsing in the next phase.

To build the resilience, or to build the capacity of adaptation is probably the key. Both call for more flexible mechanisms. This would be difficult for a system in K phase. Some local measures are feasible, but the change of the whole system may depend on external aid. There are other systems yet at the dawn of r phase. Is it possible to focus the accumulation of capital on resilience in order to facilitate the transition and reconstruction in the Ω phase?

By the way, it seems there are too few influential people in the resilience study circle. Buzz Holling, Garry Peterson mentioned in the article, and Brian Walker, they are about all and share almost the same opinion. Perhaps we can say the resilience researchers as a community is not resilient due to lack of diversity.

Dryland crisis and resilience

Crisis in the Drylands: Scientific American

If you do not want to be unpopular, just remember to criticise Mr. Bush and his ``War on Terror''.  However, after we attribute conflicts to everything from imperialism to terrorism, from religion to civilisation, I am glad to see finally some opinions which reflect on the trapped, or failure state in many arid areas, from a different aspect which has very little to do with politics and military.  The article states that:

Washington looks at many of these clashes and erroneously sees
Islamist ideology at the core. Our political leaders fail to realize
that other Islamic populations are far more stable economically,
politically and socially—and that the root of the crisis in the dryland
countries is not Islam but extreme poverty and environmental stress.

The article gracefully followed this issue by discussing what is the cause of these areas' unfavourable state, why military approach is not working and what economic and environmental measures should be taken to salvage these areas and people.  The measures include solving water shortage, increasing productivity, building infrastructures and establishing export market.  However, to apply the article's suggestion without consideration to all arid environments in such crisis may not be justified.  As each area have differing situation and conditions, and the history before they fall to the undesirable state may be worthy looking at. 

I would argue that resilience, and afterwards adaptive cycle and panarchy, can be used as a framework when studying such problems.  The objective of improvement, is not only bring people out of poverty, but also ensure that they do not fall into poverty again when another drought or war strikes, i.e. make them more resilient to changes. 

To achieve this, one question must be answered is "what state on earth is the system in?". If we use the ball and basin analogy, we say the system is "trapped" in a state because there is some forces that stop the system from shifting state, just like the terrain around a basin stops the ball from falling out.  These forces may be brought by the interactions of slowly and fast changing variables.  The article in SA noticed fast changing variables but often the slow ones are more fundamental.

It can be very tricky to find the slowly changing variable, especially in a complex system.  An examination of the system's history sometimes can help.  By identifying different periods when the system is more organised or chaotic, or when it is more resilient or more rigid, and compare variables we can get hold of, we may be able to identify slowly changing variables.  We can also identify significant changes in the history and examine its impact.  This is where the adaptive cycle comes into play.  The problem with this approach, however, is that the measures of resilience, connectedness and capital (the three dimensions in the cycle metaphor) are still quite subjective nowadays.  But comparison and qualitative analysis is possible.

From the adaptive cycle we can find out how the slowly changing variables influenced the resilience, connectedness and capital varied throughout the history, god-willing, we will be able to tell how they influence the system today.  The next step, given slowly changing variables, is to optimise fast changing variables so as to change the shape of the "basin" so the "ball" can fall into a better basin (if any, that is) than the current one.

Back to measures proposed by the SA article, they are all trying to change the fast changing variables, such as water availability and grassland productivity.  However without knowledge of slowly changing variable, such as soil texture, organic content, and/or precipitation, such manipulation may well be futile.  Not to mention there are also socioeconomic factors in play, e.g. local customs, the psychology of local people and occupant, and the impact of foreign culture.  These are even more intriguing to define and quantise.

In a word I think it is correct to begin to address dryland crisis from environment and economy sector instead of military and ideology ones.  Yet the frustrating complexity should be covered if long term interest of the system is desirable.  So far the most promising helper seems to be the resilience/panarchy network.

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Bio-fuel and resilience

Today I attended a lecture given by Alan Bullin with the topic ``Biofuels in the Asia-Pacific'', which is just a general review of the situation of biofuel legislation, adoption and application in developed and developing world. But my question would be, how biofuel crops affect the resilience of farmers who adopted them out of economic interest?

I asked this because I thought of farmers in China. If they know this is going to make money you can bet they will begin to plant sugarcanes overnight. However, their relatively slow rate to access relevant information means they are very likely to encounter market failures and have losses. On the other hand, the question is also about long-term perspectives. If one day we suddenly do not need biofuel and fossil fuels anymore (invention of safe and cheap hydrogen/nuclear/solar/you-name-it energy technologies), will the farmers be able to quickly and easily turn to other income sources?

Dr. Bullin's answer to the questions, as I perceived, is that the market will determine what the farmers plant, the adoption of new energy will not be sudden, but a gradual process. The competition between various biofuel crops means the farmers will not be trapped in one crop and cannot get themselves out. They can always turn to another kind of biofuel. Of course, in the market, there is always risk.

I did not mention resilience or China's immature market in my question, which may change his answer a bit. On a second thought, the farmers may not always have alternatives due to climate and hydrology restrictions. I still would like to know whether farmers can turn their sugar cane field into, say, potato garden quickly enough. There have already been some studies on biofuels and resilience. Many of them expressed optimistic evaluation of this new technology concerning long-term gains and resilience, stating their positive role in the conservation of forest and reduction of carbon. However, I do think there is some negative issues that should be scrutinised carefully, for example, increased food price [1], changed land use and threat to natural area/food production [2], and Fairtrade concerns.

1. [Kill king corn](http://dx.doi.org/10.1038/449637a). Nature 449, 637 doi: 10.1038/449637a (2007).
2. [Fuelling controversy -- can biofuels slow the speed of climate change?](http://www.panos.org.uk/PDF/reports/climatetoolkit1.pdf)