1 Introdution

Since time immemorial, people settle to form communities around natural resources, on which the people rely for means of livelihood and socio-economic development [1]. Parts of Iva Valley, Ugbo Odogwu, and Emene communities of Enugu metropolis have arguably evolved originally along the bank of River Ekulu, on which the residents rely for domestic water needs, means of livelihood and socio-economic development [2]. Households among these semi-urban poor live in crowded and unsanitary slums and squatter settlements without access to basic public infrastructure and services, hence they rely on common wealth and resources, such as the River for domestic water, fishing in the river, and hunting animals and gathering wild fruits from the riverbank bush [3, 4].

The availability and acquisition of these means of livelihood is predicated on sustained ecological integrity of the river and riverbank vegetation cover type. Sustainable ecosystem resource appropriation requires rigorous monitoring and management of both short-term impacts and long-term effects. This informed the establishment of twelve (12) river basin development authorities (RBDAs) in Nigeria in the 1970s to accelerate agricultural development, power generation, navigation, rural development, among other development objectives. They were to handle riverine ecological conservation and preservation through adaptive monitoring and management of biodiversity and ecosystem, ecological flow assessment of the freshwater ecosystems, measurement of hydrologic alteration and in-stream flow, sustainable resource management and development, among others. Sadly, four decades down the line (1970s–2000s), the RBDAs have not performed [5]. Similarly, the Ministries of Natural Resources, Water Resources, and Forestry have not been effective in monitoring and management of the ecosystem natural degradation, nor have they any database to capture the general decay and dysfunction of public institutions in Nigeria [6].

With a growth rate of 3.2%, Nigeria’s total population was 185,989,640 in 2016, compared to only 37,860,000 in 1950. Nigeria’s 2006 census records show that Nigeria’s population increased rapidly since the last 5 decades (1960s–2000s). For 1963, the population was 54.96 million with growth rate of 5.53%. In 1991, the population was 89 million with growth rate of 1.74%. The records of 2006 census show 140.43 million population with growth rate of 3.1%. From the 2011 estimates, the population was 162.47 million with 2.96% growth rate [7]. With a constant land mass, Nigeria’s population density has correspondingly increased. This naturally impacts negatively on the integrity of rivers in Nigeria because of the corresponding increase in consumption of natural resources, waste generation, among others. Unlike Canada with database [8, 9], a lack of database on changing River Ekulu depth, channel width, the riverbank deforestation and changing ecological integrity status of River Ekulu delimited the study to aerial images and respondent opinions for inferences [10]. Adaptation theory (also known as survival theory or survival of the fittest) [11,12,13] is about an organism’s ability to adapt to changes in its environment and adjust accordingly over time. There is a relationship between organism and its habitat. To survive, species change in response to changes in the habitat or environment (or adapt to changes in the habitat or environment). Three changes that follow habitat changes are habitat tracking, genetic change or extinction. A livelihood comprises the capabilities, assets (resources, claims and access) and activities required for a means of living. A livelihood is sustainable if it can cope with, and recover from, stress and shocks, maintain or enhance its capabilities and assets, and provide sustainable livelihood opportunities [14].

In order to survive, the population that depends on River Ekulu for means of livelihood and socio-economic development ought to respond or adapt to changing river depth, channel width and riverbank vegetation cover type? The current study targetted the household breadwinners, who rely on River Ekulu for means of livelihood and socio-economic development, in Iva Valley, Ugbo Odogwu and Emene semi-urban communities. The study aimed to investigate the changes in River Ekulu depth, channel width and riverbank vegetation cover type, their causes and effects on biodiversity and livelihood activities and adaptation to these environmental habitat or ecosystem changes. The research questions for present study were:

  1. 1.

    What are the changes in River Ekulu depth?

  2. 2.

    What are the changes in River Ekulu channel width?

  3. 3.

    What are the changes in riverbank vegetation cover type of River Ekulu?

  4. 4.

    What are the effects of changing river depth, channel width and riverbank vegetation cover type of River Ekulu on biodiversity?

  5. 5.

    What are the effects of changing river depth, channel width and riverbank vegetation cover type of River Ekulu on livelihood activities of household breadwinners who depend on the River for livelihood activities?

  6. 6.

    How do household breadwinners who depend on River Ekulu for livelihood activities adapt to changing river depth, channel width and riverbank vegetation cover type of River Ekulu?

  7. 7.

    What are the factors causing the changes in river depth, channel width and riverbank vegetation cover type of River Ekulu?

The objectives of the study were to investigate the:

  1. 1.

    Changes in the river depth of River Ekulu.

  2. 2.

    Changes in channel width of River Ekulu.

  3. 3.

    Changes in the riverbank vegetation cover type of River Ekulu.

  4. 4.

    Effects of the changes in river depth, channel width and riverbank vegetation cover type on biodiversity.

  5. 5.

    Effects of the changes in river depth, channel width and riverbank vegetation cover type on livelihood activities of household breadwinners who depend on the River for livelihood activities.

  6. 6.

    Effects of the changes in river depth, channel width and riverbank vegetation cover type on the adaptation responses of the household breadwinners who depend on the River for livelihood activities.

  7. 7.

    The factors causing the changes in river depth, channel width and riverbank vegetation cover type of River Ekulu.

Seven corresponding null hypotheses were formulated to guide the study and were tested at the end of the study. The hypotheses entailed changes in river depth, channel width and riverbank vegetation cover type; the effects of changing river depth, channel width and riverbank vegetation cover type on biodiversity and livelihood activities of household breadwinners who depend on the River for livelihood activities; adaptation of household breadwinners to changing river depth, channel width and riverbank vegetation cover type; and factors causing the changes in river depth, channel width and riverbank vegetation cover type. The null hypotheses were:

  • Ho1: There is no change in river depth of River Ekulu.

  • Ho2: There is no change in channel width of River Ekulu.

  • Ho3: There is no change in riverbank vegetation cover type of River Ekulu.

  • Ho4: Changing river depth, channel width and riverbank vegetation cover type of River Ekulu have no effects on biodiversity.

  • Ho5: Changing river depth, channel width and riverbank vegetation cover type of River Ekulu have no effects on livelihood activities of household breadwinners who depend on River Ekulu for livelihood activities.

  • Ho6: Household breadwinners who depend on River Ekulu for livelihood activities do not adapt to changing river depth, channel width and riverbank vegetation cover type of River Ekulu.

  • Ho7: There are no factors causing changes in river depth, channel width and riverbank vegetation cover type of River Ekulu.

2 Materials and methods

2.1 Study area

Enugu is a coalcity in Southeast geo-political zone of Nigeria. It is the capital city of Enugu State (1991 to date), former Anambra State (1976–1991), East Central State (1967–1976), erstwhile Biafra (1967–1970), administrative capital of the Eastern Region (1938–1960), capital of Eastern Region (1960–1967) and capital of Southern Nigeria (19). Colonialists arrived Enugu in 1903, discovered coal in it between 1909 and 1913, and commenced commercial mining of the commodity in 1915 when Udi (Coal) Mine was opened. Settlements sprang up in the Milliken Hill in Enugu-Ngwo area, Ugwu Alfred, and Coal Camp at the bottom of Udi Hills. In 1917, Udi (Coal) Mine was replaced with Iva Valley mine. From Enugu coal was exported from 1916 to Europe through Port Harcourt Seaport via the Eastern rail line. Government Reserved Area (GRA) was built as the European Quarters in 1916. By 1917, Enugu city officially gained township status to which African migrant workers rushed and developed the squatter camps on the Udi Hills and Iva Valley. Enugu became the capital of the Eastern Region after Nigeria’s independence 1960–1967, the defunct Republic of Biafra 1967–1970, the then East Central State 1970–1976, the old Anambra State 1976–1991, and Enugu State 1991 to date. The significance of Enugu lies in its status as the “capital of Igboland.” Igbos are a people kown for industrial dexterity. It is a centre of filming activities of the Nigerian Nollywood industry. Enugu houses the Akanu Ibiam International Airport, University of Nigeria Enugu campus, Institute of Management and Technology (IMT), Enugu State College of Education (Technical), Godfrey Okoye University, Caretas University, Our Saviour Institute of Science and Technology (OSISATECH), Institute of Ecumenical Education, African Thinkers Community of Inquirers College of Education, Coalcity University, and Peaceland University. Neighbourhoods of Enugu metropolis are Abakpa, Nike, Emene, Iva Valley, Ogui, Coal Camp, Akwuke, Obiagu, Garriki, Maryland, New Haven, Awkunanaw, Achara Layout, Uwani, Trans-Ekulu, GRA, and Independence Layout. Ugbo Odogwu is subsumed in Iva Valley and One-Day with Idaw River are subsumed in Achara Layout/Awkunanaw. River Ekulu is the largest waterbody in Enugu metropolis in Enugu State in Southeast Nigeria. It is 25 kms long and traverses notable settlements from Iva Valley to Emene and beyond of the metropolis. Its water and riverbank forest are of socio-economic importance to inhabitants of the neighbourhoods. The River became well known with the discovery and mining of coal in commercial scale from 1908 by the colonialists who settled miners in Iva Valley where the first mining sites were located [2, 13,14,15,16,17].

The study targetted the semi-urban poor, who depend on the fishes in the river and animals and fruits and other produce from the riverbank bush for livelihood. Iva Valley, Ugbo Odogwu and Emene semi-urban communities were purposively selected as neighbourhoods through which River Ekulu flows. They are high-density neighbourhoods commonly harbouring upwards of 700 persons per hectare, with predominant tenement house types characteristic of low-income habitation. The average monthly household income range was 20,000–50,000 naira ($40–100) at the parallel market exchange rate of N500/$ in 2021). The 2006 population census figures for Iva Valley and Ugbo Odogwu (together) was 70,545, while that of Emene was 70,021. They are susceptible to environmental habitat changes, and need to adapt to these changes to survive [18]. Preliminary inquiries showed that the semi-urban communities had mixed households whose breadwinners depended on various means of livelihood. Some of them depended on the River Ekulu for means of livelihood. Some were salaried workers who depended on personal emoluments for livelihood means. And, some others belonged to other vocations, businesses and careers.

Ezenwaji and Orji [2] showed River Ekulu as a major river traversing Enugu metropolis, but failed to show the slum settlements along the riverbank. The next major river is Nyaba River, which does not traverse many parts of Enugu metropolis. Both rivers are part of the Asata River Basin and Watershed (Fig. 1).

Fig. 1
figure 1

Source: Ezenwaji and Orji

Enugu showing the Asata River Basin and Watershed. [2]

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2.2 Study design and delimitations

The longitudinal study covered a ten-year period (2012–2021). Three (3) semi-urban neighbourhoods (Iva Valley, Ugbo Odogwu and Emene), through which River Ekulu traversed, were purposively selected. The household breadwinners, who depended on the fishes in the river and animals and fruits and other produce from the riverbank bush for livelihood. Iva Valley, Ugbo Odogwu and Emene semi-urban communities, were targetted. The study did not seek to establish the ecological integrity of River Ekulu at various points in time or season, nor to quantify the differentials in the changes in river depth, channel width and riverbank vegetation cover type, but to investigate the reality of the changes. Again, the study did not seek to quantify the differentials in household incomes, since the targets kept no records of their incomes, but were engaged in lifestyle businesses for means of livelihood and survival. Besides, the study did not seek to establish empirical data on the changing population of the selected semi-urban communities. The paucity of database in Nigeria, where environmental management institutions are weak, would not support these steps. The study rather relied on aerial images, resident respondent opinions, interpolations and extrapolations for inferences.

2.3 Sample population and sampling technique

Since the targets of the study (household breadwinners, who depended on the River Ekulu for means of livelihood) could not be delineated, isolated or sieved out, the sample size could not be determined from the study population. To obtain a sample size when there is no list for a sampling frame, snowball sampling is ideal [19]. Census sample population, which was indeterminate until sampling was concluded, was used. First, the gate-keeper (traditional ruler or town union president or neighbourhood watch group leader) of each community supplied the name and contact information on a member of the target population, who met the specified inclusion criteria. After eliciting information from the respondent, he/she revealed the next member of the target population, who also met the specified inclusion criteria, and where to locate him/her. This went on, until no other member of the target population, who met the specified inclusion criteria, was left. Thus, a census sample population of 32 (13, 8 and 11, respectively for Iva Valley, Ugbo Odogwu and Emene communities) was reached. The study included household breadwinners who had lived for upwards of ten (10) years and depended on the fishes in River Ekulu and animals and fruits and other produce from the riverbank bush for a means of livelihood in Iva Valley, Ugbo Odogwu and Emene communities. The study excluded household non-breadwinners, household breadwinners who had lived for below ten (10) years and depended on the fishes in River Ekulu and animals and fruits and other produce from the riverbank bush for a means of livelihood in Iva Valley, Ugbo Odogwu and Emene communities, and household breadwinners who did not depend on River Ekulu for a means of livelihood in Iva Valley, Ugbo Odogwu and Emene communities.

2.4 Instruments for data collection

Google form was administered to 200 experts who were purposively selected on basis of online visibility in terms of publications in the subject area. The number (N = 200) was assumed to be a census population of experts in terms of publications in the subject matter, and therefore, devoid of bias. The questions covered causes of changes in River Ekulu depth, channel width, riverbank vegetation cover type and their effects on biodiversity and livelihood adaptation. Aerial images [22] of River Ekulu were taken with a Drone from various points and seasons to estimate the river depth, channel width and riverbank vegetation cover type. Aerial photographs offer unparalleled perspectives for productions, urban planning, cinematics and other sectors. Drones do a good job of aerial photography and videography beyond aerial shots formally restricted to high-budget productions or specialized surveys. Drones have ease of use, portability and affordability, and have democratised and revolutionized capturing aerial photograph and the way the surrounding is perceived from above. Questionnaire was administered to the target population with explanations and helping the handicapped ones to write their views on the questionnaire which elicited information on incidences of changes in River Ekulu depth, channel width and riverbank vegetation cover type and their causes and effects on biodiversity and livelihood activities and adaptation by members of the target population. The instrument was of two sections: personal data and technical data. The former sought demographic information on respondents, while the latter sought information from respondents on the reality of the changes in River Ekulu depth, channel width and vegetation cover type, as well as their causes and effects on livelihood activities and adaptation. Answer options to the close-ended questions were arranged in a four-point likert scale of very true (VT, 4), true (T, 3), false (F, 2), and very false (VF, 1). Twenty-seven (27) key informants (9 per community, consisting of 3 key officers of each of Igwe Cabinet, Town Union and Women Group or leaders of community-based organisations, CBOs) were interviewed for corroboration of data from the questionnaire and aerial images, as well as for more insights.

The purpose and procedure of the study was well explained to the prospective participants (gate keepers, key informants and questionnaire respondents). Thereafter, their prior informed consent was sought and obtained both for participation in the study and publishing the outcome of the study for academic purposes with anonymity. Prior informed consent of those whose images were captured was sought and obtained both for taking their images and publishing their images for academic purposes with deliberate anonymisation.

2.5 Data analysis tools

Data from the questionnaire were analysed to corroborate the aerial images and to determine the effects of the changes in river depth, channel width and riverbank vegetation cover type on ‘biodiversity, livelihood activities and adaptation by the household breadwinners’ and to draw inferences and proposals. Data from the four-point likert-scale response options were analysed using calculated value (CV) compared with decision value (DV) to test the hypotheses. The decision rule was to reject the null hypothesis and accept the alternate hypothesis, if the DV was greater than the CV (i.e., DV > CV), and vice versa. Factor analysis was used to select the significant causes of changing river depth, channel width and vegetation cover type of River Ekulu.

3 Results

The results of the study are presented in this section. They include demographic data of gate-keepers and respondents, changing River Ekulu depth, channel width and riverbank vegetation cover type and their effects on livelihood activities and adaptation, frequency listing of 8 causes of changes in River Ekulu depth, channel width and riverbank vegetation cover type, factor weights (fw) for the significant causes of changing River Ekulu depth, channel width and riverbank vegetation cover type, and test of hypotheses.

Table 1 shows demographic data of gate-keepers.

Table 1 Demographic data of gate-keepers
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Table 2 shows demographic data of respondents.

Table 2 Demographic data of respondents
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Table 3 shows changing River Ekulu depth, channel width and riverbank vegetation cover type and their effects on livelihood activities and adaptation. Decision value, DV is the average of the likert scales: (4 + 3 + 2 + 1)/4 = 2.5.

Table 3 Changing River Ekulu depth, channel width and riverbank vegetation cover type, their causes and their effects on livelihood activities and adaptation
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Table 4 shows the frequency listing of 8 causes of changes in River Ekulu depth, channel width and riverbank vegetation cover type, as suggested by respondents. They are climate change (27) and increase in population density (26), weak laws (3), outdated laws (2), inadequate policies (2), poor enforcement of laws (2), and corruption (2).

Table 4 Frequency list of causes of changing River Ekulu depth, channel width and riverbank vegetation cover type
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Table 5 shows the first 2 items on the list generated automatically by PCA as the significant causes of changing River Ekulu depth, channel width and riverbank vegetation cover type for having factor weights greater than 0.4 (the universal minimum benchmark). The remaining six items were, therefore, insignificant and discarded. The significant causes and their factor weights were climate change (fw 0.44–0.54) and increase in population density (fw 0.51–0.62).

Table 5 Factor weights (fw) for the significant causes of changing River Ekulu depth, channel width and riverbank vegetation cover type
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4 Discussion

4.1 Demography of respondents

The gate-keeper for Iva Valley was the traditional ruler, a male aged 64. The gate-keeper for Ugbo Odogwu was the Town Union President, a male aged 42. The gate-keeper for Emene was the Neighbourhood Watch Group leader, a male aged 33. It was not customary for women to be traditional rulers, town union presidents or neighbourhood watch group leaders in these communities.

Snowball sampling yielded a census sample population of 32 (13, 8 and 11 for Iva Valley, Ugbo Odogwu and Emene communities respectively). Average monthly household income was 37,000 to 49,000 naira ($74–98 at 500 naira to a $ exchange rate in the parallel market in 2021). About 66% (21 respondents) of the 32 target census population were literate with at least the minimum literacy and numeracy educational qualification. They included 7 respondents (21.9%) with the First School Leaving Certificate (FSLC), 8 respondents (27%) with the secondary educational qualification (WASSC/GCE) and 6 respondents (18.8%) with higher educational qualifications (ordinary national diploma, OND, higher national diploma, HND or degree, OND/HND/Degree). This finding could be attributed to the influence of city dwellers on the semi-urban poor, making them to attend proliferating adult education programmes for effective interaction with neighbouring city educated dwellers. This is in tandem with citizen aspiration to improve literacy level or status, which is gaining ground in Nigeria.

All respondents were male. No woman was a household breadwinner, out of 32 target census population reached. Thus, hardly does a woman live on fishing/hunting as an household breadwinner in the studied neighbourhoods and period. Since all 32 participants were male, breadwinning businesses were not gender-balanced, but that of males. Most likely, female- and child-headed homes attached to responsible men for breadwinning and protection needed in the urban squatter settlements considered more or less as jungles. This finding aligned with the spirit of African extended family social network and corroborated earlier submissions [20,21,22,23].

The mode age bracket of participants was 36–45 (30% or 10 respondents), followed by 46–55 (24% or 8 respondents), 56–65 (23% or 7 respondents), 26–35 (14% or 4 respondents), above 65 years (8% or 2 respondents) and 18–25 (2% or one respondent). Thus, the businesses were middle-aged (36–65 years) and the productive age in the society. The younger breed, 18–25 years, who constituted only 2% or one respondent, showed that people of that age bracket might still be in school as students or training as apprentices. This finding agreed with earlier report [21, 22]. Most participants (96%) were married or widowers. This compeled breadwinners to quickly adapt to changes in the environment with regards to means of livelihood. Marital status has been reported to be a major factor influencing choice and change of livelihood [25]. Seventy-four per cent (74% or 24 respondents) had been in the businesses for 15–20 years, while 26% (7 respondents) had been in the businesses for 10–14 years, before adaptation to other means of livelihood. People dropped from the businesses as years went by.

4.2 Changing river depth, channel width and riverbank vegetation cover type, their causes and effects on livelihood activities and adaptation

Figures 2, 3, 4, 5 and 6 show the shallow river depth, narrowing channel width and riverbank vegetation cover type of River Ekulu. Specifically, Fig. 2 shows shallow river depth and narrow channel width with extending and deforested riverbank vegetation cover type. Figure 3 shows shallow river depth. Figure 4 shows patronage of the shallow river for various casual activities, as against livelihood activities. Figure 5 shows children activities in the shallow river (children used to fear the river when it was larger and deeper with riverbank forest vegetation type). Figure 6 shows expanding croping activities on the extended and deforested riverbank, as against fishing in the the formerly deep and large river and hunting in the former riverbank forest. Respondents submitted and/or corroborated these findings. Key informants revealed that a time was when River Ekulu was a large and dreaded river for economic fishing activities and with forest on the riverbank for hunting and exploitation of common wealth resources, such as fruits, firewood, among others. But, as population density of Enugu metropolis grew and climate changed, the river lowered to its current stream-like depth with children able to hop in and out of the River (Fig. 5), which had not been dared by children when it was deeper and larger with fearful forest on the riverbank. People presently crossed the river with ease like they would cross any shallow stream. Autobykes were dragged into it for washing, and across it for river crossing (Fig. 3). The depth in a rainy season was lower in the succeeding rainy season, and the depth in a dry season was lower in the succeeding dry season.

Fig. 2
figure 2

Source: Eneh

Lowering river depth, narrowing river channel width and extending riverbank with deforestation. [20]

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Fig. 3
figure 3

Source: Eneh

Shallow and adverse effect on biodiversity and livelihood activities. [20]

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Fig. 4
figure 4

Source: Eneh

Extending and deforested riverbank and adverse effect on biodiversity and livelihood activities. [20]

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Fig. 5
figure 5

Source: Eneh

Children engaging the shallow river (hitherto feared/avoided for depth and ferocious flow). [20]

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Fig. 6
figure 6

Source: Eneh

Expanding croping activities on the extended and deforested riverbank. [20]

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The environmental changes in river depth, channel width and riverbank vegetation cover type of the River Ekulu had adverse effects on biodiverty (the degree of variation of life). This supports earlier reports that attributed it to nutritional imbalance in the habitat and threats to various life forms. Fishes and other aquatic life forms and forest animals got endangered, escaped to favourable environments or became wiped out and extinct, thereby adversely affecting biodiversity and disrupting the choice and timing of livelihood activities and the socio-economic life of members of the target population. Environmental and habitat changes typically affect biodiversity and cause mass extinction [9, 24, 25].

The imbalance in biodiversity and ecosystem occasioned by changing river depth, channel width and riverbank vegetation cover type of the River Ekulu had adverse effects on livelihood activities of household breadwinners who depended on the River for means of livelihood. As life forms disappeared from the River and from the riverbank, there was decreasing means of livelihood from the water and riverbank forest. As the riverbank vegetation cover type changed, livelihood activities changed from fishing at various points of the River and hunting in the riverbank forest changed to off-season vegetable cropping. The findings, which were submitted and corroborated by participant respondents, agreed with earlier report [26, 27].

Various factors conspired to ensure lower river depth, narrowing channel width and changing riverbank vegetation cover type of River Ekulu. Participants identified climate change as a significant factor of dwindling River Ekulu depth, narrowing channel width and changing riverbank vegetation cover type. This confirmed the submission of Hosseini, Johnston & Lindenschmidt [28] that climate change reduced water quality of rivers, decreased nutrient concentrations, with a greater decrease of nutrient concentrations in open water. Yale School of Environment [29] submit that climate change raises the temperature of river water, and this reduces oxygen levels. Over time, warming rivers witness rise in pollination levels in Western nations. Climate change altered the season, qauntity of rains and drought. Dwindling river depth, narrow river channel and extending riverbank (land reclamation) also meant changing vegetation cover type with the concomitant adverse effect on biodiversity.

Participants identified increase in population density as another significant cause of lowering depth of the river, narrowing width of the river channel and changing vegetation cover type. This finding supported POPIN [30] that increase in population density and in human activities contaminated and depleted water supply and resources. These impacted imbalance on biodiversity, with some species of life forms endangered, others being wiped away and yet others extinct. The greater the population density and waste per capita, the greater the chances of stuffing wastes in drainages and river channels [2, 31]. In response to diminishing natural resources in the River Ekulu, which served for means of livelihood, household breadwinners were changing livelihood activities from fishing and hunting to off-season vegetable croping.

The population of Nigeria was only 37,860,000 in 1950, compared to 185,989,640 in 2016 with 3.2% growth rate [23]. Similarly, in 1952, 62,000 was the population of Enugu [11]. By 2006, 722,664 was the population [14]. Therefore, the population growth was 1,066% in 54 years or an annual population growth rate of 19.74%. This was one of most explosive population growth rates known in history. Thus, wastes from anthropogenic activities have multiplied over the years. By dumping the population-dependent increasinly generated wastes into the River Ekulu, the river depth lowered, the riverbank channel width narrowed down, and the riverbank vegetation cover type changed and was reclaimed for alternative livelihood adaptation activities. Since, the River was non-seasonal, off-season vegetable cropping became a booming livelihood activity, replacing fishing in the River and hunting in the riverbank bush.

A leading cause of water pollution worldwide is excessive nutrient loading of (e.g. waste dumping in) water bodies. Dumping of wastes in the River Ekulu polluted the domestic water sources, leading to adverse effect on biodiversity and livelihood activities. This agreed with earlier reports that sewage, household garbage and liquid wastes discharged into water bodies were major causes of water pollution. Also, agricultural and factory wastes, as well as solid wastes and litters dumped into water bodies were major causes of water pollution [30]. It is to address this development challenge that Target 6 of Goal No. 6 of the 18 Sustainable Development Goals (SDGs) seeks to protect and restore by 2030 water-related ecosystems, including mountains, forests, wetlands, rivers, aquifers and lakes [32,33,34].

Figure 7 summarizes the findings of the study and shows that a combination of climate change, rapid increase in population density and dumping of domestic and industrial waste and effluents in River Ekulu adversely affected biodiversity and choice of livelihood means.

Fig. 7
figure 7

Causes and effects of lowering depth, narrowing riverbank channel width, changing vegetation cover type and livelihood activities of River Ekulu

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4.3 Policy implications

The socio-economic consequences of gradual or sudden ecological disturbance can be grave in terms of loss of ecological integrity and upheavals in biodiversity and livelihood. Yet, both the government and people affected in the study area just watched ecological integrity of River Ekulu grind to a halt, through gradual changes in the, channel width and riverbank vegetation cover type, caused by climate change and high rate of population growth. This type of apathy of Nigerian government contributed to the country becoming the “poverty capital of the world” and going through frequent economic recessions. The government ought to have proactive ecological conservation programmes to prevent losses and further losses to ecosystems, ecological restoration and succession response for repairing natural sites that have been degraded, and disturbance ecology programmes to checkmate the causes and consequences of natural and artificial or man-made or anthropogenic ecological disturbances.

5 Conclusions

The study utilized a socio-ecological approach to investigate changes in river depth, channel width and riverbank vegetation cover type of River Ekulu, their causes and effects on biodiversity and livelihood adaptation in Enugu, Nigeria. Targeted household breadwinners were reached through snowball sampling technique. Analyses of data generated with questionnaire and seven null hypotheses tested revealed that there were changes in the depth of the river, width of the water channel and riverbank vegetation cover type of River Ekulu in Enugu, Nigeria during the period of investigation. The changes in the depth of the river, width of the water channel and riverbank vegetation cover type had effects on biodiversity and on livelihood activities of household breadwinners. The household breadwinners adapted to the changes by modifying occupational operation styles and changing vocations. Significant factors causing the observed changes in the depth of the water, width of the water channel and riverbank vegetation cover type were climate change (factor weight, fw, 0.44–0.54) and increase in population density (fw 0.46–0.63). The alternate hypotheses were accepted with calculated values (CVs) of 1.6, 1.7, 1.7, 1.8, 15, 1.9 and 2.5 respectively, as against 2.5 decision value (DV).

Aquatic life forms and forest animals get endangered as ecological integrity is disrupted. They escape to favourable environments or become wiped out and extinct. The adverse effect on biodiversity disrupte the choice and timing of livelihood activities and the socio-economic life of members of the target population. Household breadwinners who depended on River Ekulu for livelihood were compelled to adapt to the ecological changes by abandoning fishing and hunting for off-season vegetable crop farming on the extended riverbank.

The government and riverine neighbourhood dwellers need conscientisation on the ecological changes, their causes and effects, and ways-forward on policies and practices. Emphasis should be on the effects on livelihood and the imperative need for environmental conservation policies and implementation. Dredging of rivers needs to receive urgent attention to reverse dwindling river depth, channel width and changes in riverbank vegetation cover type and their attendant adverse effects on biodiversity and livelihood adaptation to disrupted ecological integrity.

Further studies can seek to establish the ecological integrity of River Ekulu at various points in time and/or season. Quantification of the differentials in river depth and channel width can be undertaken as well. Again, quantification of the differentials in household incomes is another study opening, even though the targets kept no records of their incomes. Another future study can seek to establish empirical data on the changing population of the selected semi-urban communities.