Digitalization challenges in education during COVID-19: A systematic review

Abstract The global outbreak of the COVID-19 pandemic crisis has led to the disruption of the learning activities of many educational institutions across the world. The transition from conventional education learning to digital learning has left both educators and students in the face of challenges. The impact of education loss was found to be more critical for students from poor and rural backgrounds. The shift of education activities to online teaching and learning has aroused growing interest in studies examining the impact of the global outbreak on the education sector. Although there had been studies in the past that have provided a literature review on the impact of the COVID-19 pandemic on teaching and learning, however, systematic review using the PRISMA approach on this particular study of interest has remained relatively less. Hence, this study aimed at conducting a systematic review by adopting the PRISMA strategy to focus on the challenges faced by the education sector during the crisis period. The results from this review found 82 articles by keywords search. Through a systematic review, the literature is extensively scanned to answer the well-defined research questions and four (4) main themes have been developed with 19 articles included in the finding synthesizing. The review conducted in this paper will contribute by providing comprehensive reviews of the past literature done specifically in examining the challenges to digitalization in learning during the pandemic crisis.


Introduction
According to a recently published policy paper by Sazuki et al. (2021), the acceleration of the digital revolution is crucial to transform education institutions in adapting to a new business environment post-pandemic. OECD (2021), United Nations (2020), and Mogaji and Jain (2020) have shed light on the state of education learning that has shifted towards an online distance approach during the pandemic crisis. Many of them have chosen to focus on the impacts of COVID-19, the readiness of the institute for a rapid shift towards online learning, and addressing current challenges to the rapid transition to distance learning. The education disruption due to COVID-19 has exposed some weaknesses of the current education system which may seem to have been poorly adapted to the new changes.
The prolonged impact of the COVID-19 lockdown has caused deprivation to rural students' access to e-learning. This pointed out the exacerbation of education disparities because of the crisis. Many of the rural students were unable to keep up with their education due to the lack of infrastructure and other socio-economic problems. Hence, resulting in the consequences of learning loss within this underprivileged group. These students are likely to lose the most in terms of educational outcomes and the support provided if the countries take insufficient measures to promote education equity and inclusion (OECD, 2020).
A policy brief by United Nations (2020) supported that there could be an exacerbation of disparities in learning opportunities following the shifting of learning towards an online approach. Analysis of statistical data has pointed out that education inequalities tend to be neglected during a pandemic crisis leading to learning loss for marginalized groups. It is expected that the learning loss will cause a reduction in average learning levels, a widening gap in learning achievements, and an increase in dropouts. UNESCO provided an estimation that there could be about 23.8 million dropouts due to the pandemic's economic crisis alone.
Prior works by Al-Kumaim et al. (2021), Kee and Adamu (2021), and Ma et al. (2021) have investigated extensively how the pandemic crisis affected the education sector. Al-Kumaim et al. (2021) presented various obstacles encountered by students through descriptive analysis and developed a conceptual motivational model for sustainable online learning. Meanwhile, Kee and Adamu (2021) provide a commentary paper on the higher education realm in Malaysia and discourse analysis to outline the impacts and challenges of the pandemic crisis on the higher education sector. Abdullah et al. (2020) further developed a conceptual framework as a response to the COVID-19 pandemic. The developed framework describes the interrelationships concerning the resilience of Malaysian higher education.
Motivated by the past studies that shed light on the challenges of the COVID-19 crisis to the education sector, this paper intends to conduct a systematic literature review to explore further the challenges presented by the rapid digitalization in education during the pandemic crisis. A systematic review is best employed as it can be used to identify and critically synthesize pertinent literature on a certain subject. This study will, therefore, contribute to the research literature in the following ways: First, it provides an in-depth insight that examines and analyzes the past research done in this area specifically. Secondly, this study will seek to explore what are the limitations and gaps in this research. Thirdly, recommendations will be given on the possibility of future study directions that can be performed in this specific area of study.

Methodology
This study employed PRISMA (Preferred Reporting Items for Systematic reviews) for its search strategy and systematic review approach on the articles selected. The use of PRISMA will extensively scan all literature published on the subject to find answers to the clearly defined research question, and to that end use various inclusion and exclusion criteria to identify the reports to be included in the review, and then synthesize the findings. The search for relevant literature was conducted across the Scopus database which is one of the largest academic literature databases. Elsevier Scopus is a citation database containing more than 50 million records from around 5000 publishers (Grimaldi et al., 2017). Besides that, many local universities in Malaysia including ours acquired and emphasised the Scopus database. This is the main justification behind the decision to use the Scopus database as our main data source. The articles considered for the selection were the ones that are related to the scope of the study. The scope built for this study revolves around the impacts or challenges of COVID-19-induced digitalization in the education sector. Figure 1 shows the use of PRISMA as the search strategy.
The systematic search begins by using a combination of keywords as shown in Table 1. The preliminary search across the database retrieved 82 articles. By restricting the search to the document type "Articles" and limiting it to "English" written language only, the search was reduced to 38 articles. The abstract and full text of these articles are then manually screened and accessed based on the inclusion/exclusion criteria in Table 2. Only articles that satisfied the inclusion criteria will be included in the systematic literature review. Based on the inclusion/ exclusion criteria, 19 articles have been included in the review. The use of systematic review is well justified for this study as this methodology is highly suitable to be used when the dataset is small enough for the review to be performed manually. Besides that, this approach also ensures that the selection of relevant studies goes through a well-structured, rigorous, replicable literature review and provides a more objective overview of the search results and avoids any bias (Cropanzano, 2009;Post et al., 2020;Tranfield et al., 2003). The 19 articles found will then be clustered into 4 main clusters in answering the research question as follows: (1) What are the challenges from the transition of traditional learning to online learning for higher education (HE)?, (2) What are the digital competence and teaching pedagogy challenges experienced by the    (4) What are the challenges that lie in the effort to achieve a sustainable digitalized education system as a whole?

General findings and background of study
Generally, the employment of PRISMA will allow articles to be selected and grouped into macro themes. The flow of the diagram clearly describes the process of identification and screening based on the eligibility, inclusion, and exclusion criteria of the literature that fall under the scope of the review. A systematic review is a structured approach to analyzing the background literature, which seeks to prevent potential biases arising from purely narrative analyses (Pittaway et al., 2004). In view that the systematic review on this particular subject theme has remained relatively young with many potentials offered for future study, this study will contribute to providing literature contributions. The review from this paper illustrated the paradigm shift in the way that quality education is being delivered and this paves the way for future digital learning enhancement. The global outbreak of the pandemic COVID-19 has put a pressing need for all countries to innovate their teaching and learning in mitigating the disrupting effect on their education sector. Much of the existing literature has been found of interest to report and highlight the impact of the COVID-19 pandemic on the teaching and learning process by countries. As such, this paper will synthesize these existing studies to generalize and provide a comprehensive report on the challenges of rapid digitalization and its sustainability, especially towards achieving SDG 4 Quality Education.
The selected articles are then examined thoroughly and the contents are extracted as follows: (1) author(s) and year of publication, (2) title, (3) sample country, (4) methodology, (5) main findings reported. The literature is then coded and categorized into four research clusters for an indepth analysis using a predatory reading approach. The research clusters identified are as follows: (1) Challenges of Transition to Online Learning, (2) Digital Competence and Pedagogy Challenges, (3) Inequality in Education and Psychological Challenges, and (4) Challenges to Sustainable Development of Digitalized Learning. Table 3 presents the results of the review conducted on the selected literature following the codification as aforementioned. Following the identification of the four research clusters as presented in Table 3, each cluster will be examined in detail for critical reflection and to recommend future research directions in connection to this topic.

Challenges of transition to online learning
The outbreak of the COVID-19 pandemic has brought major disruption to the education sector and necessitated the transition to online teaching in many countries as a measure to ensure the continuity of learning. The rapid transition from physical learning to online learning has led to new challenges for both educators and students. A systematic synthesis of the literature gathered found six articles that studied the implications of such transition that took place during the pandemic crisis.
The systematic synthesis of all six articles leads us to draw a general conclusion that the transition to online teaching and learning has undeniably caused many challenges to the education sector. All the research had agreed that the pandemic has accelerated digitalization by providing analysis on the effects of such changes. Generally, most of these papers were found to be focusing the analysis on the higher education sector (Nurhas et al. (2021), Kaqinari et al. (2021), Hurria (2021), Mary and Hlaing (2021), Márquez-Ramos, (Márquex-Ramos, 2021)). Hence, there are clear limitations of these studies with the need for more analysis focusing in particular on primary and secondary education sectors.
It is important to note that, based on the review, the insight provided on the challenges encountered from the digitalization of the education system is analyzed from different perspectives. For example, Nurhas et al. (2021) has analyzed the challenges based on three different levels of analysis consisting of individual level, interpersonal/group level, and organization level. Meanwhile, some studies use a comparative approach to explore the effects across different countries. However, there could be limitations to such studies as it may be difficult to generalize some of the findings to other countries since the results may involve cultural bias, economic and geographical differences.
Based on this review, the challenges observed from the transition to online learning in higher education can be summarized into three main sub-clusters. These sub-clusters are (1) Technological Tools Challenges, (2) Digital Skills and Competency Challenges, and (3) Attitudes of Acceptance.

Technological tools
In the first sub-cluster formed, the literature discussed on the technology tools challenges from using online learning in higher education. For example, Mary and Hlaing (2021) in their survey of the effects of COVID-19 pandemic on higher education institutions in Myanmar reported that the lack of devices and internet facilities are generating problems for posing knowledge and understanding of a course. In addition, parents are also not monetarily strong in setting up digital learning system for online classes. Similarly, Cone et al. (2021) highlighted the massive use of digital education technologies as the chief strategy to deal with the pandemic crisis. The acceleration of the pandemic crisis that forces the closure of educational institutions has set out the investigation on the different processes of emergency digitalization spanning from Italy, Germany, Belgium, and the Nordic countries by Cone et al. (2021). The results from their findings have both mapped and problematized the possible implications for the future of European education systems. Another study by Márquex-Ramos (2021) draws light on the unequal access to technology as another major challenge. The exacerbation of inequalities between the elite and marginalized group of educators and students may further broaden the digital divide. If digitalization continues to intensify the inequalities in higher education, this will definitely bring negative impact to the students' academic performance

Digital skills and competency
Meanwhile, the second sub-cluster was focused on the challenges from the lack of digital skills and competency required in implementing e-learning. According to Cone et al. (2021), the mass closures of universities generated demand for digital forms of remote teaching and learning, but most institutions lacked the hard and software, skills, and expertise required to provide such solutions. In another paper by Nurhas et al. (2021), Q-Methodology was used to explore the challenges of rapid digital transformation that arise during the pandemic in the higher education context. Their paper reported the findings at individual-level analysis, and three challenges were identified: (1) adverse effects of technology on mental health, (2) greater dependence on digital competence (digital skills and intelligence), and (3) blurring the boundaries of personal and workrelated (as an employee or student) activities to use technology. The changes in a new set of digital skills and competence has put a high demand on work and created mental stress for both the lecturers and students. Greater workloads using new digital technologies will require reupskilling to effectively use the digital tools and techniques in e-learning.
Likewise, Kaqinari et al. (2021) agreed that the burden of ad hoc adopting and adjusting to the new situation of online learning remained with the lecturers. The need for lecturers to engage more deeply in using educational technology may pose as a new and overwhelming challenge for some of them. Meanwhile, Hurria (2021) explored the challenges faced by the higher education sector during the COVID times in Australia and reported that there will be paradigm shift challenges as new models will be required for teaching and learning. It was also reported by Hurria (2021) that teachers have found online teaching platform to be much more challenging than the face-to-face traditional classrooms with students tending to keep their cameras off while attending lectures. There is less engagement with the phenomenon of "Ghosting" being observed by the lecturers. The increased use of digital technology has resulted in the replacement of face-to-face teaching and is affecting the trilemma in higher education (Márquex-Ramos, 2021).

Attitudes of acceptance
The third sub-cluster examined the challenges for students and lecturers in accepting the transition towards e-learning. The research by Mary and Hlaing (2021) showed that most of the teachers and students interviewed in higher institutions in Myanmar agreed with the changes implemented in the higher education system. Higher education institutions should seek to use technology and new ways of lesson delivery need to be designed under the new system. Another study by Kaqinari et al. (2021) employed a comparative approach on lecturers from four European universities focusing on the switch to online teachings during the COVID-19 lockdown. The focus of their study was to identify the individual and institutional factors that either facilitate or inhibit the transition from conventional teaching before the pandemic to online teaching during the COVID-19 lockdown. Their findings suggested that both self-efficacy and attitude play a crucial role in the application of education technology. The correlation found between online teaching self-efficacy and perceived success was consistent with Bandura (1986). In addition, the inter-correlation matrix results also reported a positive correlation between online teaching self-efficacy with attitudes towards educational technology and intentions to adopt pedagogical practices in the future. In addition to personal factors, external factors such as teaching load may also have a significant impact on the use of educational technology. Meanwhile, Hurria (2021) reported some initial resistance to changes to online learning from students and educators. Some of the educators dropped out of teaching during COVID, while others went through a steep learning curve.

Digital competence and pedagogy challenges
The shift from traditional face-to-face learning to digital learning has resulted in challenges for educators, with obstacles in digital competence and pedagogy changes. Several papers have shed light on the difficulties posed by the digitalization of education to educators during the pandemic crisis. Based on the review carried out, most articles were found to provide insight into the implications of the emergency online transition from the educator-centered viewpoint (Damsa et al., 2021;Korhonen et al., 2021;Watermeyer et al., 2021). Discussion on the multifaceted role of digipedagogical and innovation competence in the changing educational context has been demonstrated by studies such as Korhonen et al. (2021). Similarly, Treve (2021) provided a discussion on some of how COVID-19 may develop new strategies for pedagogy and posited technology as something positive. The study by Aroles and Küpers (2021) also supported the need for educators to reflectively move between embodied and digitalized forms of education and provided perspectives regarding the development of an integral pedagogy. It is clear, therefore, that pandemic-induced digitalization has resulted in tremendous challenges for educators in the context of pedagogy and digital competency. The challenges observed from this aspect can be further summarized into two main sub-clusters. These sub-clusters are (1) Online Pedagogy and (2) Professional Digital Competence Skills.

Online pedagogy
Online pedagogy is based on the same principles of traditional teaching, but adapted to the digital environment. The goal is to create a learning experience that is engaging, interactive, and effective, while also taking advantage of the unique features of digital technologies. In one of the literature reviewed, Watermeyer et al. (2021) has suggested that online migration is engendering significant dysfunctionality and disturbance to the pedagogical roles and personal lives of academics. Based on the respondents' accounts, digital transitioning has worsened the preexisting crisis not just for the students but for academics as well. The study revealed that precarisation, proletarianization, and performativity continued to proliferate as academic careers became more tenuous with the transition of digital pedagogies. According to Treve (2021), the transformation to online teaching meachanism, adoption of student-centered learning model, and interactive sessions coupled with high chances of students' distractions have called for an innovative pedagogy that posed as a major challenge for teachers.
In another study, Damsa et al. (2021) examined the responses by the academic teachers' agency following the physical closure of institutes and emergency online migration. A theoretical model has been formed to elucidate how teachers are adjusting their teaching with the acceleration of education digitalization. Overall, teachers reported that they lacked pedagogical knowledge and needed to seek out forms of support beyond the regular support provided by their institution. Aroles and Küpers (2021) explained that the challenges of online pedagogy were more concerned on the path through which to re-embody differently teaching and learning activities within a virtual format. In other words, the embodied digital teaching is a skill to be mastered. The challenges, therefore, lie at the need to design pedagogies and to organize resources in digital education that scafford the bodily, effective and interactive dynamics constitutive of understanding in a particular domain. Learning materials and activities that "reshape" learners' current physiological and affective reactions in necessary ways enable engagement with and commitment to the learning process. Interestingly, Akhmetshin et al. (2021) highlighted on the process in designing the pedagogy within the context of digitalization. The proposed model using the new e-learning technologies ensures the required quality and efficiency of the design, implementation, and management of the content of professional training of students in universities.

Professional digital competence skills
Professional digital competence entails the capacity to use digital resources for education constitutes professional. Treve (2021) discussed the difficulties that educators are facing as face-toface teaching has made a transition to "online pedagogy." The key obstacles identified in this study are the technical resources and differential access to education. Besides that, teachers' competencies have been identified to play a significant role in the successful transition from offline to digital mediums. According to Damsa et al. (2021), teachers have been frequently reported as not being acquainted with digital technologies, lack of competence, and insecurity about the technology used in pedagogical settings as main constraints. Good online teaching requires a digital infrastructure, digital and pedagogical expertise and support, and a community of teaching practice where online teaching is subject to collaborative development initiatives.
In the context of the COVID-19 pandemic and the sharp transition to remote learning, new problems have appeared in the operation of digital educational systems and technologies (Akhmetshin et al., 2021). An analysis of the problems of e-learning revealed challenges such as a lack of relevant training materials, technical failure, lack of opportunities for continuous learning, and a decrease in the speed of transmission and information processing. Korhonen et al. (2021) explored how Finnish primary school teachers organized virtual workplace collaboration during the emergency distance education forced by COVID-19. Based on their analysis, three groups of enablers of distance education were identified, namely, (1) the adoption of digital technology, (2) the digipedagogical competence of the teachers, and (3) the ability of teachers to act as adaptive innovators. It was found that the teachers' ability to adapt pedagogical and digipedagogical expertise becomes a critical success factor when the emergency change is forced on the education field.
The digitalization acceleration brought upon by COVID-19 has resulted in an online transition for many programs including STEM-based courses that require a hands-on approach. Sukumaran et al. (2021) analyzed the status of STEM education in Malaysia to explore the challenges of e-learning integration with STEM-based courses. Their study highlighted the importance of both the "hard structure" (referring to technology hardwares such as platforms, applications, tools, etc.) and the "soft structure" (encompassing people-related aspects including the management support and educators' knowledge and skills institutional structures) for a successful e-learning implementation. In another study, Pölzl-Stefanec (2021) extended the analysis of the challenges and barriers to Austrian early childhood educators' participation in online professional development programs. The study supported that the field of early childhood education must be more strongly integrated into the expansion of digital infrastructure and technical equipment. The content of early childhood educators' professional development programs must be adapted to IT competencies.

Inequality in education and psychological challenges
The COVID-19 pandemic crisis has been observed to be having a profound impact on all students, especially on the most vulnerable ones that are facing additional barriers against the digitalization of education. These students will risk falling behind academically due to the lack of access to digital learning resources and tools. The resulting learning loss could further lead to the loss of skills that is related to the productivity of labours. In addition, the pandemic crisis also poses a risk of emotional problems to the learners. The challenges observed from this aspect can be further summarized into two main sub-clusters. These sub-clusters are (1) Inequality of Access and (2) Psychological Limits.

Inequality of access
According to Hanushek and Woessmann (2020), the loss of skills due to the learning disruption during COVID-19 could result in a 1.5% lower gross domestic product (GDP) throughout the remainder of the century and proportionately the economy could be suffering a higher percentage of losses if the education systems are slow to recover to its prior levels of performance. In addition, the move to implement emergency remote teaching through online platforms has induced anxiety among the students. This implies that the digitalization of education due to COVID-19 has resulted in socio-psychological implications for students. In view of this, a few strands of research literature had put the study emphasis on the aspect of the socioeconomic inequalities widening and the psychological impact of COVID-19 among students. According to Radina and Balakina (2021), the pandemic illuminated the issue of inequality in education that had worsened as a result of the emergency transition to online studies. In particular, they have focused the review on the most vulnerable groups of students such as children from low-income families, children from migrant backgrounds, and students with disabilities.
A systematic review of past research indicated that the first wave of research on the inequality in education during the COVID-19 pandemic dealt with the most obvious problems of socioeconomic deprivation of children from low-income families who used to receive support from educational institutions pre-pandemic. The review also highlighted that families with low socioeconomic status may suffer from an extremely inconducive distance learning environment. Besides that, students in rural areas could face the challenges of digital tools and equipment unavailability, poor internet connection, and even inconsistent power supplies that inhibited the learning process completely. These studies especially shed light on the widening of educational inequality during the pandemic. Students from vulnerable social groups such as students from lowincome families, from migrant backgrounds, or those from rural areas are found to be most adversely affected as they lack access to the digital learning conducted during the pandemic crisis. In line with Helm et al. (2021), this result suggests that students in socially underprivileged contexts would suffer more during the transition to online learning. This indicated the presence of social inequalities during distance learning.

Psychological limits
Meanwhile, Tannert and Gröschner (2021) aimed to investigate the risk of emotional and motivational problems posed by the displacement of physical learning at school to online learning at home. The results of the analysis of the present study on students from secondary schools demonstrated that the students' perceived joy during the crisis was relatively low while the perceived anxiety was relatively high. The regression analysis outcomes showed that the relationship between the joy in learning during times of crisis and self-efficacy belief was in turn influenced by environment predictors such as support from family and school as well as the student-teacher relationship. Apart from that, the study presented also revealed that support structures are well suited to buffer negative effects on emotional well-being, motivation, and learning outcomes. The closures of education institutions due to COVID-19 pandemic pose a severe rupture in learners' school life with a reduction in social contact and lesser opportunities to engage with their peers and teachers. All these constraints result in the students' poor emotional and motivation constitution.
According to Radina and Balakina (2021), the difficulties of integrating distance learning formats could be psychological due to unfamiliar format of classes and diminished motivation. This in turn leads to a decrease in learning effectiveness. In the past, the focus of the scientific literature was more on addressing the general consequences of the COVID-19 crisis and lockdown to the education field and very specific aspects such as its effects on the academicians. However, there are relatively few investigations of the impacts from students' perspectives. Hence, the research by Radina and Balakina (2021), Tannert and Gröschner (2021) can contribute by analyzing the consequences of the rapid digitalization of education from a student-centered viewpoint instead. The issue of the possible psychological implications inflicted on students as they are pressured by the trying times of COVID-19 has been demonstrated by researchers as well.

Challenges to sustainable development of a digitalized learning
As COVID-19 is shaping a more digital society through the process of rapid digitalization, the focus on digital competencies should be built upon a sustainable digital society in the development of digitainability (José Sá et al., 2021). The digitalization of education is related to life improvement in the context of sustainable development (Toader et al., 2021). Sustainable education is seen as important in promoting balanced growth. Hence, a study of the challenges of promoting sustainable development of a digitalized learning environment becomes increasingly important. In line with this, the studies by Denisov et al. (2021), Toader et al. (2021, and José Sá et al. (2021) aimed to examine the effects and challenges of digitalization on education from the aspect of sustainable development. For example, the study by Denisov et al. (2021) focused on distinguishing between educational approaches that seek to sustain the "unsustainable" and identifying the problems of lecturer-student interaction amid the mass transition to online learning. The challenges observed from this aspect can be further summarized into two main sub-clusters. These sub-clusters are (1) Digital Literacy and (2) Digital Sustainability.

Digital literacy
Digital literacy is essential for people to participate harmoniously in society as both users and creators of digital technology in a conscious, deliberate, intentional manner, which is essential for sustainable development, especially in a post-COVID-19 context. In a digital society, literacy is crucial for promoting sustainability. Digital literacy in particular, along with general literacy, is a potent tool for empowering people and giving them the skills they need to succeed in both their personal and professional lives. In one of the studies, Toader et al. (2021) employed the pooled mean group (PMG) and mean group (MG) to investigate the effects of digitalization on higher education in a sustainable development framework. The result of their study demonstrated a positive effect of tertiary education on sustainable development. The findings from their analysis suggested that public policies in education should consider strong investments in digitalization and the implementation of new technologies as a premise for sustainable development. Meanwhile, José Sá et al. (2021) sought to analyze what digital competencies post-COVID-19 are necessary for the development and consolidation of a sustainable society and, more specifically, digitainability in a COVID-19 pandemic context. In their study, they highlighted the importance of digital literacy in promoting sustainability in a digital society.
The systematic synthesis of the relevant publications provided vital information about the development of a sustainable digitalized learning environment. The present studies reviewed have indicated the need to equip students and teachers with digital competencies that will be able to build a sustainable digital society. Digital literacy is crucial for the harmonious participation of individuals, providing empowerment to them not just as consumers but as creators of digital technology which is crucial for sustainable development (José Sá et al., 2021). Apart from that, it is necessary to reduce the digital divide that could hinder sustainable development. The digital divide is visible in the inequalities of access, both in physical terms and at the digital literacy level, which is a profound challenge in the mobilization of digital resources. The significant finding of the indirect positive effect of digitalization on sustainable development by Toader et al. (2021) provided support for promoting the acceleration of digital transformation in education. A critical society recognizes that digital literacy is a fundamental skill in the digital age. Therefore, digital sustainability must prioritize promoting digital literacy to ensure that everyone has the knowledge and skills to navigate the digital world effectively.

Digital sustainability
Digital sustainability refers to the responsible use of digital technologies and resources to promote environmental, economic, and social sustainability. This concept recognizes that the growth and development of the digital economy have significant impacts on the environment and society, and thus it is essential to promote sustainable practices in the digital world. In a critical society, digital sustainability means considering the impact of digital technologies on social justice, equity, and democracy. Study by José Sá et al. (2021) sought to analyse what digital competences post-COVID -19 that are necessary for the development and consolidation of a sustainable society and, more specifically, digitainability in a COVID-19 pandemic context. José Sá et al. (2021) presented six main characteristics of digital sustainability that are viewed as paramount. These six characteristics are (1) intergenerational justice, (2) regenerative capacity, (3) economic use of resources, (4) risk reduction, (5) absorptive capacity, and (6) ecological and economic added value. Education processes are therefore deemed to be crucial in fostering digital sustainability in a digital society with active learning. With the use of digital technology in education for sustainable development, the school thus provides a crucial contribution to social cohesion and social fairness. The advantages of digitalization for sustainable development are undeniable, but only nations and educational systems that fully support the development of digital competences in students will give their citizens the skills they need to thrive and succeed in both their personal and professional lives (José Sá & Serpa, 2020).

Discussion on literature gap and limitation
From the systematic review analyzed, it can be observed that extensive research has been done in this specific area of interest. Hence, highlighting how pertinent and paramount this issue has been. Despite that, these interesting findings have not been extensively reviewed in the past. It would be worthwhile to explore these findings, which would no doubt provide insight into how this particular area of study has evolved. With this aim, a systematic review will provide a discussion of the most comprehensive available literature conducted. On the whole, the study of most papers has been limited to empirical findings. Hence, the systematic review conducted in this study will contribute to filling the literature gap by classifying these studies into specific clusters for more effective discussions. In addition, the review of each cluster also highlighted the limitations of the available studies. For example, researchers under the cluster of "Challenges to transition to online learning" has been limited to country-specific studies. As such, this paper encourages further exploration of the lessons that can be learned from the constraints and challenges experienced during the delivery of lessons and learning facilitation during the pandemic crisis.

Recommendation and conclusion
Based on the systematic review conducted on the existing studies, this study has presented the negative implications of the emergency migration to online learning from a general perspective and explored the effects from the academicians' viewpoint and based on the students' experience. The critical review extended the evaluation of the psychological impact of COVID-induced online learning on students and the widening of the learning gap between students of different backgrounds. The critical analysis of the available literature also provided evidence of pedagogy challenges to teachers as they prepare for the shift to an emergency-based online learning system. Findings from the literature have identified the teachers' competencies as a significant factor in ensuring a successful transition from traditional physical learning to digital-based platform learning. Several articles addressed the concerns of the challenges in developing a sustainable digitalized education environment. Digital literacy has been identified as a critical component for the consolidation and development of sustainable education in the era of COVID-19.
Four (4) main themes have been developed from this review, and literature was clustered based on these themes, namely, (1) Challenges of Transition to Online Learning in Higher Education (HE), (2) Digital Competence and Pedagogy Challenges, (3) Inequality in Education and Psychological Challenges, and (4) Challenges to Sustainable Development of a Digitalized Learning. The first theme mainly highlighted the challenges posed by the online learning transition with a special focus on higher education (HE). The articles Kaqinari et al. (2021), Nurhas et al. (2021), Mary and Hlaing (2021), Hurria (2021), Márquex-Ramos (2021), Cone et al. (2021) discussed how the higher education sector responded to the pandemic outbreak by turning towards the introduction of digital teaching and learning. Beyond doubt, the transition of teaching and learning would bring many challenges to these countries especially those that are less prepared and are struggling to adapt to such changes due to a lack of infrastructure.
In the subsequent theme, the highlight has been drawn to the challenges from the aspect of teaching pedagogy as many educators have reported the struggles they experienced in adapting to the new teaching innovations. The limited skills and digital competency have made the teaching process more difficult as educators find it extremely strenuous to practice the conventional skills that they have been equipped with from their teaching colleges. Meanwhile, the next theme concluded on the psychological impact of learning digitalization has on students that tend to be largely overlooked in the past. The struggles of the students in adapting to the new learning environment have taken a toll on them and left many suffering from mental stress. Besides that, students from poor backgrounds were unable to follow the lessons due to the lack of electronic gadgets needed for online learning activities. This has led to the widening of the learning gaps between students of different backgrounds.
The last theme reported on the issue of the sustainability of the education process's rapid digitalization. This issue is of vital importance to ensure the achievement of one of the sustainable development goals (SDGs), SDG 4 Quality Education, which has been strongly advocated by the United Nations. Based on SDG 4, the objective was to promote inclusivity and equitable education opportunities toward lifelong learning for all students irrespective of their backgrounds. Despite the sudden migration of instructional delivery to online platforms during this time of crisis, the challenges experienced by academicians and students are well explored and transformed into opportunities, and online learning will be sustained (Adedoyin & Soykan, 2020). In line with this, the systematic review presented in this paper would contribute to the existing literature by providing a critical reflection on the implications of the COVIDinduced digital learning transition.
A comprehensive analysis of the available evidence provides key insight into the challenges of emergency remote learning during COVID-19 that can be used to suggest future research areas. In addition, the knowledge obtained from this critical review will be useful to analyze the evolution of the research in this area of interest and to identify the limitations of these studies. The result from this review provides a few important recommendations, (1) Policy intervention from the government is crucial in ensuring the sustainability of teaching and learning innovations, (2) Professional training is needed to equip educators with digital competency and necessary IT skills, and (3) Adequate infrastructures such as network connectivity and digital learning tools need to be enhanced in ensuring that no students are left behind in their learning process, (4) Online teaching pedagogy needs to be creative, and the educational tools need to be more interactive to improve the learning process efficiency. Hence, a future study that is in line with the above recommendations would be useful to prepare the education system in paving way for future digital learning processes. In addition, the future focus study should be oriented on the sustainability of the education innovation process in ensuring that such changes are in line with the sustainable development goals (SDGs).

Disclosure statement
No potential conflict of interest was reported by the author.