From the result presented in chapter four, inferences were drawn from various variables in order to assess the causes and effects of tree removal on the University of Ibadan Campus.
Species of trees removed, numbers and locations of trees removed: Thirty-eight tree species removed from twenty (20) families were identified from different locations. Prominent trees that were removed in these areas in an order of reducing frequency were Delonix regia, Albizia glaberima, Terminalia catapa, Gliricidia sepium and Antiaris africana among others.
Tree Species removed, numbers and location on Campus
Residential Areas: Delonix regia had the highest number of removal in the stratum (56) followed by Albizia glaberima (24) were removed. Also, Twenty-one Casuarina equisetifolia, Terminalia catapa (12), Gliricidia sepium (11) ,Antiaris Africana (9), were some of the prominent species removed during the course of the last 10 years. The presence of more trees removed in the residential can be explained by the fact that there are more trees in the residential areas more that other areas on campus
Administrative Areas: More of Albizia glaberima were removed in this stratum as against Delonix regia that were removed in S1. Out of the trees species that were removed, Albizia glaberima, Azadirata indica and Delonix regia were more prominent. Magnifera indica, Millettia thonningii, Gliricidia Sepium and Spathodea campanulata had one removed each. There is a reduction in species richness and diversity from S1 to S2 which may be due to hard impervious surfaces around the administrative areas. This agrees with Ajewole (2005) which states that the urban environment is generally characterized by impervious surfaces, highly reflective and radiating materials like concrete, and metals.. This agrees with the findings of Omole et al,. (2009)that Samena sena pose a highest level of hazard as they are most likely to fall , this may be attributed to the fact that most municipal trees within the university community survive on construction-altered soils that may be compacted, poorly drained, littered with construction debris and landscape maintenance. All these cumulative stresses are expected to take a toll on tree vitality and structural integrity, increasing the risk of failure.
Residential Areas: There were seventeen species of trees removed in S3. Also, Albizia glaberima, Terminalia catapa and Delonix regia are the most prominent with 13, 11 and 9 respectively. Other Species like Ficus mucuso, Lamea welwistchiiand Gliricidia sepium .
Parks and Gardens : Thirteen (13) species were removed with their total number of trees observed to have been removed being 36 .Antiaris Africana and azadirata indica have the highest number of their species removed while Albizia glaberrima, Casuarina equisetifolia, Delonix regia and Triplochyton schleroxylon had 3 removed each. Ceiba petandra, Miliscia excels and Blighia sepium had one removed each. . This also agrees with findings of Omole et al,. (2009) that there are large trees which present a great hazard on campus, hence the need for their removal.
Reasons for Tree Removal as perceived by respondents: Table 3 shows that 86.5% of the respondents noticed tree removal on campus. 56.2% perceived that the reasons for tree removal are due to old age, 42% believed that the trees removed especially at the Faculty of Education area due to constructions going on there. Also, 34.9% believed that the trees were removed due to destruction of roads and buildings. 35% believed the trees were removed due to wind throwing, this agrees with the findings of Omole et al,.(2009) that most of the trees on University of Ibadan Campus are as old as the University itself
Reasons for Tree Removal on Campus as documented by Campus Biodiversity Committee: From Table 4, we can deduce that of all various reasons as documented by biodiversity committee, Old Age was the most prevalent. This agrees with the findings of Omole et al,.(2009)who reported that most of the trees are as old the University and that many changes in the University campus over the last fifty (50) years have greatly stressed many of the trees resulting in decline tree canopy that is grossly undermanaged. Omole et al,. (2009) reported that trees having multiple defects are hazardous within the University of Ibadan community. Also, as reported by the biodiversity committee Samena sena have rooting abilities that grows into underground facilities, road and building foundations. This also agrees with the findings of Omole et al,. (2009)who reported that the potential for damage is extremely high and high for Delonix regia and Samena sena respectively but Samena sena has a potential to cause more infrastructure damage. Also, there were cases of trees removed due to infrastructural developments on campus especially Faculty of Technology, Human Nutrition, Faculty of Education amongst all.
Some other species like Samena sena, Khaya ivorensis, Terminalia catapa and Terminalia ivorensis were removed because they possess heavy crowns and their canopies grows into roofs and damage buildings.
Uses of Trees and Maintenance of Trees on Campus: From Table 6, 98.8% of the respondents had trees in their compound, faculty, office or hostel and 37.7% could give the estimated number of trees. 929 trees were reported to be present in respondents offices/hostels/compounds or faculties, this agrees with Eguakun and Nkwor (2019) which states that the University environment is rich with diverse avenue tree species because of the benefits of trees in the environment.
The respondents uses the trees for wide range of benefits which includes research and education, collection of fruits and leaves, relaxation such as sitting under shades, beautification, protection from winds and reduction of noise in the factories like sawmill. This agrees with the findings of Afolayan (2009).
Also, from the result obtained, 71% reported that the campus biodiversity committee was involved in tree maintenance which agrees with the findings of Omole et al,. (2009)that University of Ibadan campus tree biodiversity committee are responsible for removing or otherwise treating hazardous tree growing on campus property, they are also responsible for maintaining urban tree canopies, thereby minimizing unjustified removals.
Perceived Effects of Tree Removal on Campus: Analysis from Table 7 shows that 88.5% of the respondents love to live or work in an environment with natural or planted trees. This agrees with the findings of Afolayan(2009) which states that lots of people love to live in an environment with natural or planted trees.
65.5% of the respondents reported tree removal on campus as being undesirable because of the numerous benefits they derive from the presence of trees around them which includes purification of atmosphere, heat reduction and fruits and leaves productions among others.
Also, 34.5% reported tree removal on campus as being desirable because of potential hazards, littering of their environment such as hostel/offices/houses and walkways and also destruction of campus infrastructures such as buildings, roads, electric cables, underground facilities and others.
62.5% would not support the continuation of tree removal as against 37.5% that would support it. This implicates that trees on campus would enjoy active participation of public on campus trees, tending and maintenance and also maybe participation in tree planting programs on campus.
Also, it shows from Table 8 that the respondents have ample knowledge about environmental hazards like erosion, flooding e.t.c. and television and social medias are the major sources of disseminating information. This implies that lots of people watch television and are very active on social medias.
High temperature on campus was reported by the majority as the effect of tree removal experienced on campus, while 62.9% had experienced storm and 27.9% had experienced flooding.
Also, 80% of the respondents knew tree removal on campus is the major factor responsible for the hazards and 93% believed that reforestation and replacement of trees removed can help to mitigate the effects. The implication of these is that University of Ibadan being an academic environment, many people has knowledge about urban tree reduction and deforestation.
Relationship between location and reasons for tree removal: The P-Value of the chi-square from table 9 which is 0.011 shows that there is significant association between tree species locations and reasons for tree removal. Therefore we do not accept the null hypothesis. This implies that the locations of trees have their impact on the reasons for tree removal. Areas like residential areas are more prone to tree removal. There are lots of trees that are old on campus especially the residential areas. This agrees with the findings of Omole et al,.(2009) who reported that 94 trees along Oduduwa Road of the campus were hazardous. This also agrees with the findings of who reported that most of the trees are as old the University and that many changes in the University campus over the last fifty (50) years have greatly stressed many of the trees resulting in decline tree canopy that is grossly undermanage. Due to threat to lives, buildings and properties around the residential areas, there is need to remove these trees.
Relationship between Tree Species Removed and reasons for removal.: The P-Value from table 10 which is of 0.54 shows that there is no significant association between species of tree removed and reasons for tree removal. Therefore we do not reject the null hypothesis. This implies that the trees removed does not have any impact on the reasons for removal. This also agrees with the findings of Omole et al,. (2009) which states that the defects observed in the municipal trees within the campus are common to all the tree species.