As indicated by Hull [5] , conceptual advancement is motivational engine for scientific progress. Following this perspective, it is a good reason to explore and clarify ecosystem resilience concept given that it is as theoretical and conceptual “building blocks” of sustainability transformation.

Holling [6] first introduces ecosystem resilience as a concept emphasizing the existence of multiple stability domains in ecological system and the capacity and persistence of ecosystem when facing disturbances. Accordingly, ecosystem resilience is defined as measure of the persistence of systems and of their ability to absorb change and disturbance and still maintain the same relationships between populations or state variables [6] or magnitude of disturbance that can be absorbed before the system changes its structure by changing the variables and processes that control behavior [7] . Correspondingly, engineering resilience refers to the time a system takes to recover from a disturbance [8] or as rate and speed of return to pre-existing and original conditions after disturbance [7] . The difference is that ecosystem resilience rejects mechanical equilibrium, and concentrates on the possibilities of systems to flip into an irreversible alternative basin of attraction, while engineering resilience emphasizes “global stability” and the existence of a one single and stable equilibrium [6] . Simple put, engineering resilience is obsessed with “efficiency, constancy and predictability [9] ”.

Unfortunately, there is a tendency when continuing to develop and broaden ecosystem resilience concept that ecosystem resilience is mistakenly interpreted as “returning and recovering original and pre-existing normal state” or “maintaining and preserving what we have” [10] . As Tanner, et al. [11] argue, “to avoid thinking about things more radically; it is a convenient word like resilience or sustainability and has moved from an initial more radical meaning to one that is likely to be co-opted into existing system which want to avoid transformation.” In other words, ecosystem resilience in many cases and discourses explicitly and implicitly boils down to engineering resilience as “bounce back” [12] . If ecosystem resilience itself has confusion about what it is and what it will be, its successors might easily head in the wrong direction. It is that issue that the 2.2 Section now turns to.

Given that ecosystem resilience has been channeled into wider research fields with multi-conceptual structure dimensions. It begs an inevitable question that: Since ever-increasing definitional meanings and practices in various scientific disciplines, on the one hand, result in diversity which to some extent can improve richness of resilience approach and promote communication between and among different scientific researches, on the other hand, ambiguousness which can undermine and dilute the original power in resilience approach [13] , based on what essence in resilience concept can conceptual structure diversification be encouraged while conceptual clarity power be conserved? The word of essence is defined as: “the basic nature of a thing―the quality or qualities that make a thing what it is” [14] ; “the intrinsic nature or indispensable of something, especially something abstract, which determines its character” [15] . In other words, essence as the basic abstract nature of resilience concept meaning that determines its scopes, directions and applications in conceptual development can be explicitly or implicitly presented in diverse conceptual variants and derivate―in part or in whole.

Obviously, the underlying connection to original meaning is still implicitly and well conserved and then inherited by successors, although the term, resilience, has been endowed different definitions (Table 1), employed by multiple disciplines so as far to be changed considerably compared to the original definition. The original ecological meaning of resilience is defined as “measure of the persistence of systems and of their ability to absorb change and disturbance and still maintain the same relationships between populations or state variables” [6] . We argue that this definition is composed of six interconnected and replaceable “building blocks”: persistence, populations, ecosystems, disturbance, ability and collapse. Not only do these building blocks include state, dynamics, process, forces and systems, but also combine together to define research object, subject and direction.

It can be found that the conceptual development following original-ecosystem resilience concept is built by in-depth re-exploring the above six building blocks such as substituting one or more elements and then recombining them. One typical case is that resilience concept is introduced into social system [16] , ecological-economic system [17] [18] , or social-ecological system [19] - [21] , respectively, in which cases system is reset. Other typical examples are manifested as substituting research object while still in ecological system or deepening ecosystem dynamics [7] [22] - [28] . Thus, our proposition is that the essence of ecosystem resilience the capacity and process of positive changes and changing the changes positively between persistence and collapse or between 0 and 1 [28] with or without external disturbances. As such, the key words are capacity, process, persistence and change. In Oxford Dictionaries [15] , persistence is defined as: 1) continuing firmly or obstinately in an opinion or course of action in spite of difficulty or opposition; 2) continuing to exist or occur over a prolonged period; 3) remaining within the environment for a long time after introduction; 4) remaining attached instead of falling off in the normal manner. By definition, it indicates that “to continue when facing difficulties while still within critical threshold in long-time dimension” is the core meaning of persistence, which also signifies existence and even sustainability of social-ecological systems. Persistence and collapse exhibit the extreme endpoints on the spectrum of the conceptual meaning of resilience. Change as effect and cause of persistence can positive, or negative, and irreversibly incremental or radical. The connotations of ecosystem concept are that: resilience as system property can be studied in different systems, e.g., ecological system, social system, social-ecological system, and different systems can have different combinations of capacity, process, persistence and change, the option of which combinations depending on specific research plan and different philosophy perspective are not contradictory (be it Antropocentric or Ecocentric). It is obvious that the essence of ecosystem resilience is open, inclusive and fundamental dynamic. In the next section, we will turn to the meaning of ecosystem resilience based-resilience thinking.

Data Adapted from Fridolin Simon Brandt and Kurt Jax, 2007.

Resilience thinking rooted in ecosystem resilience is developed resting on a range of research papers and books, among which Resilience Thinking: Integrating Resilience, Adaptability and Transformability, is the most quintessential of papers. The promising endowments of this paper are that: 1) ecosystem resilience is extended from ecological system into social-ecological system; 2) another new two concepts, adaptation and transformation are added as essential perquisites for social-ecological resilience; 3) confusion between resilience and transformation is tactfully resolved by “multi-scalar and temporal resilience” perspective; 4) three aspects of social-ecological system is addressed: resilience as persistence, adaptability, transformability [10] . So, to put is another way, resilience thinking provides a conceptual and theoretical entrance by which we can genuinely integrate the ecological sphere and the social sphere, that is, social-ecological system and can map feedbacks and interactions between resilience, adaptation and transformation in multi-spatial and temporal level onto social-ecological system. However, it is a pity that resilience and adaptation is, implicitly or explicitly, similarly understood as “maintenance”, “recovering to the original state” or “business as usual” when applied in wider research fields, like climate change research, community research and disaster research, to name a few. As O’Brien [30] points out, in the process of dealing with global environmental change most studies have paid much close attention to accommodating changes, though, which also focuses on transformative changes, while less attention to creating changes proactively. Just like ecosystem resilience is trapped into engineering resilience zone, resilience thinking, which erroneously is guided by engineering resilience, is fettered by adaptation determinism.

Tracing research development founded on resilience thinking, we identify two basic conceptual dimensions of resilience thinking, we call, social-ecological non-evolutionary resilience and social-ecological evolutionary resilience (Table 2), which recognition is helpful to tell between resilience and adaptation, and between ecosystem concept and engineering concept.

As shown in Table 2, social-ecological non-evolutionary resilience is characterized as: buffer capacity for preserving what we have and recovering to where we have; all about absorbing shocks; survival and bounce- back ability and process; avoiding negative regime shift and keeping staying the “original” regime; adaptive resilience, while social-ecological evolutionary resilience thinking is featured as the ability to change, adapt, and

importantly transform with or without external disturbance and as the process to continually reinvent and innovate for doing new things and new possibilities with hope; not necessarily about absorbing shocks; bounce forward, to-forth and bounce beyond ability and process; to change and not to continue doing the same thing and to be stronger and better than before; positive and active regime shift with intentionality of human actions; transformative resilience. Among them, the two concepts, adaptive resilience and transformative resilience are widely used, which zooms in the separation between adaptive capacity and transformative capacity, between adaptive process and transformative process. Adaptive resilience refers to “the various adjustments (incremental changes) that people undergo in order to continue functioning without major qualitative changes in function or structural identity [31] ,” while transformative resilience [32] directs its attention to the capacity and ability to revitalize communities, cities, or regions with radical new relationships, modes of organization, and networks, not just returning to normal or the status quo or a pre-trauma.

It is apparent that the social-ecological evolutionary residence takes root in ecosystem resilience; social-eco- logical non-evolutionary resilience in engineering resilience. The term, social-ecological evolutionary resilience is inspired by [12] [33] . Simmie and Martin [33] reconsider resilience as ongoing changing process rather than just the capacity to recovery by linking evolutionary perspective with resilience thinking in study of regional economic resilience in order to avoid the “equilibrist trap” in the concept of resilience thinking, or to put it another way, the conflations between ecosystem resilience and engineering resilience. Davoudi [12] [34] follows this discussion and proposes, she calls, evolutionary resilience, instead of social-ecological resilience: an unceasingly changing process and a “becoming”, not as a settled property and a “being”. Thus, evolutionary resilience draws attention to the process and ability of complex social-ecological system to change, adapt, and more importantly, transform, instead of “back-to-normality”, which coincides with the essence of ecosystem resilience we suggest. It is social-ecological evolutionary resilience to we should turn as theoretical and conceptual foundation for sustainability transformation. The reason why we use the term, social-ecological evolutionary resilience, is that we accentuate change process and ability playing in the stage of complex adaptive social-ecological system, not ecological system or social system. It means that social-ecological system as a unique system differs from ecological system and social system, which is consistent with resilience perspective and sustainability science. Social-ecological evolutionary resilience as a weathervane can direct the development of interdisciplinary research when translating resilience thinking into, or integrating resilience thinking with other research fields. As Mcevory and Fünfgeld [35] argue, there are two prominent inconsistences and alienations: to mostly concern with “staying the status quo”, while to ignore transformation potential and process; to bound itself within “engineering resilience” which underlines “bouncing back to the previous stable state as soon as possible”. Nilakant, V., et al. [36] argue that there are two dimensions constituting resilience concept, one of which is called first-order resilience involving pre-disasters activities, while the other of which is second-order resilience or adaptive resilience referring post-disasters responding, learning and renewing activities. Obviously, these two dimensional resilience concepts mostly situate themselves within social-ecological non-evolutionary resilience or adaptive resilience. Sustainability transformation is usually defined as “shifts that fundamental alter human and environmental interactions and feedbacks [4] ” or as “physical and/or qualitative changes in form, structure, or meaning-making [37] ” or as “the capacity to create untried beginnings from which to evolve a fundamentally new way of living when existing ecological, economic, and social conditions make the current system untenable [38] ”. Apparently, these above definitions of sustainability transformation match with social-ecological evolutionary resilience perfectly. But it is worth noting that social-ecological non-evolutionary resilience and social- ecological evolutionary is not completely opposite to each other, which depends on concrete research subject and object. To great degree, social-ecological non-evolutionary resilience only expresses naïve appeal and comfort. In other words, we can choose to return and recover, but not to the original one, to a “new original one”, to this point, which is connected with social-ecological evolutionary resilience.