Analysis of deforestation pattern in the Niger Delta region of Nigeria

Figures & data

Figure 1. (a) Location map of study area. (b) Land use categories, 1987. (c) Land use categories, 2002. (d) Land use categories, 2013.

Table 1. Error matrix.

Classified data	Wetland	Waterbody	Forest	Sandbar	Settlement/exposed surface	Cropland/secondary vegetation	Row total
1987
Wetland	336	0	7	0	0	0	343
Waterbody	1	601	0	0	0	0	602
Forest	11	0	19,946	0	464	4262	24,683
Sandbar	0	0	0	845	39	0	884
Settlement/exposed surface	0	0	0	0	21,640	161	21,801
Cropland/secondary vegetation	0	0	73	0	463	34,068	34,604
Column total	348	601	20,026	845	22,606	38,491	82,917
2002
Wetland	890	0	20	0	14	0	924
Waterbody	0	5954	0	0	0	0	5954
Forest	14	0	38,714	0	841	7327	46,896
Sandbar	0	0	0	1477	59	0	1536
Settlement/exposed surface	0	0	4	7	1,26,348	5035	1,31,394
Cropland/secondary vegetation	0	0	400	0	1452	22,550	24,402
Column total	904	5954	39,138	1484	1,28,714	34,912	2,11,106
2013 image
Wetland	29,642	0	0	0	25	0	29,667
Waterbody	0	2812	0	0	0	0	2812
Forest	0	0	1,17,940	0	159	12,864	1,30,963
Sandbar	0	0	0	3627	1535	0	5162
Settlement/exposed surface	0	0	0	0	1,47,810	3434	1,51,244
Cropland/secondary vegetation	0	0	1875	0	3713	3,28,393	3,33,981
Column total	29,642	2812	1,19,815	3627	1,53,242	3,44,691	6,53,829

Table 2. Accuracy assessment.

Land use class	Reference total	Classified total	Number correct	Number wrong	Producer’s accuracy (%)	User’s accuracy (%)	KIA
1987^a
Wetland	343	384	336	48	97.96	87.5	0.98
Waterbody	602	601	601	0	99.83	100	1.00
Forest	24,683	20,026	19,946	80	80.81	99.60	0.74
Sandbar	884	845	845	0	95.59	100	0.96
Settlement/exposed surface	21,801	22,606	21,640	966	99.26	95.73	0.99
Cropland/secondary vegetation	34,604	38,491	34,068	4423	98.45	88.51	0.97
Total	82,917	82,917	77,436	5517
2002^b
Wetland	924	924	890	14	96.32	98.45	0.98
Waterbody	5954	5954	5954	0	100.00	100.00	1.00
Forest	46,896	46,896	38714	424	82.55	98.92	0.99
Sandbar	1536	1536	1477	7	96.16	99.53	1.00
Settlement/exposed surface	1,31,394	1,31,394	1,26,348	2366	96.16	98.16	0.95
Cropland/secondary vegetation	24,402	24,402	22,550	12,362	92.41	64.59	0.60
Total	2,11,106	2,11,106	1,95,933	15,173
2013^c
Wetland	29,667	29,667	29,642	0	99.96	100.00	1.00
Waterbody	2812	2812	2812	0	100.00	100.00	1.00
Forest	1,30,963	1,30,963	1,17,940	1875	90.06	98.44	0.98
Sandbar	5162	5162	3627	0	70.26	100.00	1.00
Settlement/exposed surface	1,51,244	1,51,244	1,47,810	5432	97.73	96.46	0.95
Cropland/secondary vegetation	3,33,981	3,33,981	3,28,393	16,298	98.33	95.27	0.90
Total	6,53,829	6,53,829	6,30,224	2,36,055

Notes: ^aOverall classification accuracy = 93.35%; Overall Kappa Index of Agreement (KIA) = 0.90.

^bOverall classification accuracy = 92.81%; Overall Kappa Index of Agreement (KIA) = 0.87.

^cOverall classification accuracy = 96.39%; Overall Kappa Index of Agreement (KIA) = 0.94.

Table 3. Land use/cover gain/loss analysis.

Land use/cover	1987 (km^2)	2002 (km^2)	2013 (km^2)	Average annual rate of change (%)
				1987–2002	2002–2013	1987–2013
Wetland	632.94	781.90	970.86	0.02	0.05	0.02
Waterbody	408.02	401.78	106.47	−0.00	−0.07	−0.03
Forest	9522.70	6901.65	5076.26	−0.02	−0.04	−0.02
Sandbar	61.82	83.66	157.81	0.02	0.14	0.06
Exposed surface/settlement	2498.31	6010.85	3463.04	0.09	0.04	0.01
Cropland/secondary vegetation	9796.09	8740.05	13140.26	−0.01	0.03	0.01

Figure 2. Land use/cover gain/loss between 1987 and 2013.