To effectively address the topic, it is essential to clarify the distinction between curriculum and syllabus. According to [37] and [17], the curriculum is often regarded as a broader concept than the syllabus, defined as “the overall plan or design for a course” that organizes course content into a structured framework for teaching and learning to achieve intended outcomes. In contrast, the syllabus specifies how selected content from the curriculum is organized into specific teaching and learning units ([37]).

[46] identifies multiple dimensions of the curriculum, including the intended, enacted, assessed, learned, and hidden curriculum. The intended curriculum specifies what learners are expected to learn, which aligns with the content focus this essay aims to analyze. The enacted curriculum represents what is actually taught, while the assessed curriculum captures the knowledge and skills learners demonstrate through both formative and summative assessments. The learned curriculum includes both intended and unintended outcomes of the educational process. Finally, the hidden curriculum, as described by [2], refers to the implicit messages conveyed by the inclusion or exclusion of certain content or individuals within the curriculum.

According to [24], curriculum content should consider the course environment, learners’ needs, and teaching and learning principles. The goals of a language course often focus on key areas such as language, ideas, skills, or text. Making well-informed and justified decisions about content is a critical aspect of effective curriculum design ([24]).

As [37] emphasizes, the development and implementation of language teaching programs can follow various approaches, each with distinct implications for curriculum design. Among these, central design prioritizes methodology-driven content, where teaching methods shape the selection of content. This approach can promote flexibility of the curriculum by focusing on learning processes rather than specifying detailed outcomes ([7]; [41]). In contrast, forward design, as seen in models like Content-Based Instruction (CoBI) and Content and Language Integrated Learning (CLIL), begins with a content-driven syllabus. It integrates content and language as the foundation for curriculum design, trying to ensure structured learning outcomes. Additionally, backward design starts with specifying desired learning outcomes. Content and instructional methods are developed to achieve these predefined outputs, positioning content as the endpoint rather than the starting point ([44]).

These approaches reflect different priorities: central design focuses on flexibility and methodology, forward design emphasizes structured content, and backward design relies on systematic needs analysis to outline objectives and guide content development ([44]).

The term “sustainable” was first introduced by [8], who advocates for the sustainable use of forests to decrease deforestation. Sustainability, often defined as environmental quality and human well-being ([30]: p. 671), is concerned with the future of our planet, the survival of humanity, and the quality of life. It has found its rightful place in educational context, and1 plays an important role both in the teaching and learning practices ([27]; [40]). As global environmental issues intensified, the [42] developed the Sustainable Development Goals (SDGs) to provide a comprehensive framework for addressing global challenges, including poverty, inequality, climate change, and environmental degradation. In this context, integrating sustainability into education is not optional but essential for addressing pressing global challenges and contributing meaningfully to the SDGs ([13]; [28]).

However, sustainability in education extends beyond simply introducing environmental topics into the curriculum. It encompasses the economic, social, and environmental dimensions, which is essential for cultivating responsible global citizens ([19]; [47]). In recent years, authors have emphasized the need to incorporate non-traditional aspects of sustainability in educational curricula. According to [16], sustainability in TESOL is closely intertwined with race- and class-based social injustice, as the effects of climate change and environmental degradation disproportionately impact those who are least able to alter the material conditions of these threats. Similarly, [35] underscores the importance of redefining sustainability frontiers by integrating new issues and paradigms. They stress the inclusion of dimensions such as ethics, aesthetics and culture, alongside non-material values like mutual help, solidarity, and compassion, which have often been overlooked in traditional approaches. Moreover, there is also a growing emphasis on collaborative working, intercultural awareness, and interpersonal skills, recognizing that we as individuals are inherently connected to their communities at local, national, and global levels ([5]). This broader perspective ensures that sustainability education fosters not only environmental consciousness but also the values and skills required to become informed, responsible global citizens ([47]).

In ELT, integrating sustainability presents a distinct opportunity. Language learning goes far beyond vocabulary and grammar; it serves as a dynamic tool for shaping perceptions, attitudes, and behaviors ([4]). Through sustainability-focused ELT, educators can utilize the English language as means to inspire environmental action and promote sustainable practices across diverse cultural contexts ([11]; [33]). However, [16] observe that many educators in TESOL have overlooked the connection between English teaching and broader sustainability crises, such as climate change, habitat loss, food insecurity, and the threat of nuclear conflict, and see this as ideological impositions ([28]), hence, it is worthy examining the content of a curriculum through the lens of sustainability so that educators can identify opportunities to embed sustainable principles into language teaching.

From a sustainability perspective, the curriculum demonstrates a noteworthy strength, that is, its effective integration of human and environmental themes. To explain, the thematic contexts in this curriculum include “man and self”, “man and society”, and “man and nature”, discussing topics like natural ecology, environmental protection, disaster prevention, and space exploration. For instance, Unit 5 of the compulsory textbook, titled “Man and Nature”, includes reading passages on global warming and wildlife protection, and a project-based task asking students to propose a local environmental protection plan. This integration not only fosters students’ interest in learning but also enhances their critical thinking and problem-solving skills. As highlighted by [9]), embedding sustainability themes into education helps students comprehend the interconnectedness of humans, nature, and society, thereby developing systemic thinking. Similarly, [43] emphasize that incorporating sustainability education into the classroom enables teachers to guide students through future-oriented perspectives and value-based reflections, equipping them to analyse complex social and environmental issues. Furthermore, [23] demonstrate that project-based learning effectively combines sustainability topics with real-world challenges, promoting students’ ability to solve problems in practical contexts. This approach deepens students’ understanding of cultural connotations and social responsibilities during language acquisition, creating a more meaningful and enriched learning experience ([47]).

While the curriculum shows some strengths, it demonstrates critical shortcomings.

First, it fails to explicitly connect English language learning with lived, local, and sustainable places. For example, Unit 3 covers “Natural Disasters” through a reading about the 2008 Wenchuan earthquake, but the activities focus primarily on comprehension questions and vocabulary exercises, with no explicit task that guides students to investigate disaster preparedness in their own communities. Similarly, Unit 7 addresses “Space Exploration” without connecting to economic or social equity issues. This disconnect undermines the potential to create a more holistic and place-based learning experience that fosters ecological awareness and a deeper sense of connection to the learners’ immediate environments. As [28]) argue, ELT classrooms often approach knowledge abstractly rather than relating it to the physical world and real-life contexts.

In a similar vein, [12] highlights in his exploration of place-based ecopedagogy that grounding English language learning in local and sustainable contexts enables students to not only enhance their language skills but also engage with discourse models of sustainability and ecological selfhood. This approach aligns language instruction with the principles of ecological and social sustainability, making learning more relevant and transformative. Moreover, Eyraud emphasizes that integrating place into the TESOL curriculum helps students build local knowledge, strengthen ties between people and their environments, and develop an awareness of the more-than-human world. As [25]) suppose, developing an ecoethical consciousness comes from teaching and learning ways to think and behave that help recognize ways we are negatively impacting our communities, while also developing “ways of thinking and acting” that create and protect our communities in just and sustainable ways. These outcomes are critical for fostering a deeper understanding of sustainability and addressing the displacement often felt by ESL and EAP learners, as noted by [15].

However, the curriculum analyzed lacks a clear place-based focus. While it introduces environmental themes, these are predominantly global or abstract, with little instruction on how learners can relate them to their local contexts. For instance, although the curriculum content includes topics such as “environmental protection” and “disaster prevention”, students are not explicitly encouraged to explore local environmental issues or participate in community-based activities which can bridge language learning with actionable sustainability practices. This absence may lead to a gap between what students learn and how they can apply it meaningfully within their lived experiences, reducing the potential impact of the curriculum on fostering sustainable habits and ecological self-awareness ([20]).

Second, the curriculum’s focus on environmental issues is somewhat narrow. It fails to comprehensively address the multidimensional aspects of sustainability, particularly in the social and economic domains. Sustainability encompasses three intersecting dimensions: environment, economy, and society, with the environment as its foundation ([6]; [48]). While the content explores topics such as “natural environment and natural heritage protection”, “natural disasters and prevention”, and “the relationship between human survival, social development, and the environment”, the discussions involved remain superficial and lack deeper exploration of multileveled critical issues such as resource overconsumption, biodiversity loss, climate change, unlimited economic growth, and the shadow of armed conflict ([16]). Surveys show that Chinese students tend to associate sustainability with terms like “green” and “environmental protection”, often overlooking the vital roles of social and economic development ([45]). In reality, environmental education is only one component of sustainability education, and true sustainability can only be achieved by integrating all the environmental, social, and economic dimensions holistically.

At the macro level, curriculum design must treat sustainability as a foundational component rather than a supplemental topic. First, it is recommended to incorporate interdisciplinary and transdisciplinary approaches by integrating sustainability themes through subjects such as environmental science, geography, and ethics ([22]; [21]). As [14] argue, this holistic method offers unique transformational properties, explicitly integrating values to promote a global perspective aligned with collective well-being ([26]). Furthermore, curriculum frameworks should create space for collaborative and self-directed learning opportunities focused on broader global topics, including gender equality, economics, and planetary health ([4]). This empowers students to analyze information critically from multiple perspectives and act as proactive agents of change ([5]; [39]). Ultimately, successfully mainstreaming sustainability requires supportive policies, such as revising curricular frameworks and allocating more time for sustainability themes, to foster an environment that encourages innovative pedagogy ([29]; [31]).

At the meso level, content selection should prioritize authentic materials and real-life scenarios to bridge the gap between language learning and sustainability. Authentic resources facilitate meaningful engagement by immersing students in discussions about global challenges and viable solutions ([1]). Crucially, materials should be localized to reflect students’ personal concerns and lived experiences. For instance, educators can utilize resources that examine how climate change impacts refugee learners ([32]) or analyze local environmental issues, such as the language used in the construction of a nearby open-pit copper mine ([32]). By grounding ecological well-being in learners’ realities, materials transform abstract concepts into tangible issues. To address the current shortage of sustainability-oriented educational materials, the development of Open Educational Resources (OERs) presents a promising solution ([18]; [36]). Collaboratively creating and freely sharing lesson plans and multimedia content can effectively address resource gaps and provide differentiated knowledge across disciplines.

At the micro level, classroom pedagogy serves as the primary site where language learning and ecological awareness intersect. Teachers play a critical role in shaping classroom interactions and implementing effective teaching strategies to promote sustainable development ([38]). Pedagogical approaches should encourage learners to reflect on how sustainability issues directly impact their communities, thereby placing their values at the center of the learning process ([10]). Language learning must remain central within these pedagogies, enabling students to use English as a practical tool for articulating ideas and advocating for sustainable practices ([34]; [3]). However, to execute these pedagogical shifts, teachers require adequate preparation. Professional development initiatives, such as workshops, specialized training programs, and educator learning communities, are vital to equip ELT teachers with the necessary knowledge and confidence ([47]). Addressing these pedagogical and preparation gaps is essential for overcoming organizational barriers and aligning sustainability topics with language-learning objectives.