1. Introduction
Among the global challenges in the 21
st Century, LUC is a rapidly growing environmental problem [
1], negatively altering the entire functions of Earth [
2]. Recent studies [
3,
4,
5,
6] confirm that the pressures of LUC inflicted on Earth’s ecological functions have been pervasive and intensive, resulting in unprecedented deterioration in global ecosystems and biodiversity over the last few decades. In this study, LUC refers to the conversion, modification, and management of landscapes/natural ecosystems/ primarily by human activities [
7]. It is a long-lasting phenomenon derived from the effects of human and natural factors; essential for socioeconomic development and ecological balances [
8]. Nevertheless, the widespread and intensive LUC, predominantly, massive transitions from natural ecosystems to human land uses have been observed over the last few decades because of increasing land and natural resources demand for agricultural activities [
7,
9], urbanization and industrialization [
10] accompanied by environmentally harmful development strategies [
3]. Despite the short-term contribution to socioeconomic enhancement [
11]; these land transition processes are strikingly jeopardizing the earth’s ecosystems and biodiversity [
4,
12]; with estimated loss of >63% of ecosystem services [
13]. As a result, people worldwide, largely in developing countries have suffered from catastrophic environmental and socioeconomic challenges: climate change [
2] and chronic poverty and food security [
1].
Following the multitudinous impacts of human-triggered LUC and degradation; sustainable conservation and use of biodiversity have become the agendas of researchers, planners and governments and measures have been undertaken from local to global levels [
3]. Designating biodiversity hotspot sites as protected areas(PAs) is one of the measures taken [
6]. Biodiversity hotspots are natural ecosystems, characterized by a significant concentration of flora and fauna diversity with a high level of endemism but susceptible to anthropogenic impacts [
14]. PAs including National parks are conceived as the most important strategy for sustainable biodiversity conservation with marked improvement in ecosystems and the services they provide [
6,
15,
16,
17]. They have been also recognized as productive places for restoring critically/endangered species and maintaining ecological integrity [
12]. Generally, cognizant the potential advantages, the area and number of PAs have shown a radical increment; today there are over 155,584 PAs worldwide [
18]. However, due to rapidly growing human encroachments, PAs worldwide are under pervasive LUC and multifaceted ecological problems including massive habitat conversion and degradation, biodiversity loss, and species extinction [
14,
16]. The magnitude and adverse impacts are more deleterious in PAs found in developing countries because of cumbersome demographic, socioeconomic, political, and administrative challenges [
12,
17], specifically in Sub-Saharan Africa region where more than 82% of the PAs are under the state of deterioration/failures with 10% only in success/recovery [
10].
In this region, Ethiopia has been recognized as one of the countries rich in biodiversity with a wide range of ecosystems [
6]. Nevertheless, over the last few decades, due to rapid and intensive land conversion from forest, grass and woodlands to agricultural and settlement areas [
9,
19] and massive wood production for multitudinous socioeconomic benefits [
20] coupled with unsustainable land management practices [
21], the country has faced a substantial cascading of ecosystems and biodiversity; subsequently with serious land degradation and socioeconomic crises: prolonged poverty and food insecurity [
22]. These situations coupled with aggressive population growth have forced anthropogenic pressures toward biodiversity-enriched/hotspots/areas and markedly worsened the deterioration of biodiversity and ecosystem services [
6,
23]. To tackle the daunting impacts of environmental degradation and preserve biodiversity-enriched areas from anthropogenic pressures, the government of Ethiopia has established different PAs including twenty national parks since the 1960s [
24]. However, like other developing countries, PAs in Ethiopia including NNP (where this study was undertaken) have been under extensive LUC and degradation due to significant habitat conversion to agricultural and settlement areas, livestock grazing, and fuel and construction wood production [
25,
26,
27]. Moreover, LUC and the resulting impacts such as habitat and biodiversity degradation are aggravated by the expansion of invasive species, recurrent wildfires and weak administrative measures [
6]. There by, currently, almost all PAs have lost their functionality, the survival of many wildlife has reached a critical stage and they stand on the verge of failure [
28].
Among gazetted PAs, NNP is the most biodiverse [flora and fauna} with a large number of endemic and critically/endangered species in Ethiopia [
29] and multifold ecological and socioeconomic advantages [
6]. Considering the huge potential for biodiversity conservation, it has been registered as one of the major African floristic areas and global biodiversity sites [
27]. Nevertheless, NNP is currently one of Ethiopia’s Pas that extremely vulnerable to human-induced LUC and degradation where natural resources are the primary source of livelihood, economic and sociocultural practices for rapidly growing millions of semi/pastoralists and urban dwellers living in and around the park [
30].
In general, the pressing loss of functionality of Ethiopia’s PAs is mainly attributed for anthropogenic-driven habitat conversion and degradation. Thus, to monitor the ongoing changes, restore degraded ecosystems and direct the future management and anthropogenic use plans toward sustaining the functionality of PAs; analyzing and mapping of the spatiotemporal dynamics of LUC is imperative. Although several studies have been conducted to address the problems of PAs in Ethiopia, the attention given to analysis and mapping LUC dynamics is scant [
25,
26,
27,
30,
31,
32,
33,
34]. Moreover, the LUC observed at any spatiotemporal level is characterized by interdependent and complex steps, transition patterns, and processes and also has a relationship with changes in other spatiotemporal levels [
35]. Analyzing the entire LUC processes comprehensively and concurrently via a robust model with rigorous procedures is, therefore, necessary for sound conclusions, informed decisions and enhanced management plans [
35,
36]. Specifically, a detailed assessment and precise measurement of land transition patterns and process for PAs is imperative to show the extent of the change to local people and improve their awareness, identify vulnerable ecosystems, examine key transition and stationary patterns, and develop ecosystem-targeted restoration and protection strategies. However, the previous studies in PAs including NNP did not assess the complete LUC characteristics and have failed to provide full information about change processes and patterns. Even at the national level most of the studies have focused on some aspects of LUC [
8]. Thus, the change analysis methods applied in these studies were not enough to accommodate all the necessary steps, patterns and processes of LUC and considerably excluded the effects of length of time intervals, areal extent, and strength of the changes, which markedly discourage, planners, policy and decision-makers from informed decision and policy-making processes for sustainable management and use of biodiversity.
Furthermore, due to considerable deviations in anthropogenic pressures, and ecological setups of PAs, the magnitude and transition patterns of LUC have deviations as shown by earlier studies in Ethiopia and other developing countries [
17,
37,
38]. Thus, for a better understanding of the change extent and also to make actionable strategies considering conditions at local level including, demographic and socioeconomic variables; analysis of LUC for each protected area is extremely crucial and recommended by many researchers [
25,
26,
37,
39]. Therefore, based on the mentioned gaps above, this study aimed to quantify the entire LUC characteristics in NNP at three levels(interval, category and transition) using a compressive mathematical model; intensity analysis [
35] from 1986 to 2002 (First Time Interval /FTIS/), and 2002 to 2020 (Second Time Interval/STIS/). The study also answered the following questions; in which the study’s time interval, the overall change intensity is fast/slow? which land types’ gain and loss are active/dormant? Why? Which land types are most intensively increased or decreased? Why? which transitions are most intensively avoided/targeted by a given land use type? which transitions in which land types are stationary across the study time interval? Finally, what is the implication of LUC observed in NNP for biodiversity, wild animals’ habitat, and livelihoods?