SECTION 3 LANDSCAPE


LAND COVER

Land cover affects the provision of ecosystem services and measuring land cover change over time is critical to evaluating and monitoring trends in natural resource condition.

Changes in land cover have many potential drivers, including human activities and natural phenomena. Examples of human activities that drive land cover change include urban development, crop and pasture management and industrial activity. Natural drivers of land cover change include flood events, bushfires and seasonal climatic variation. Attribution of specific causes to observed land cover change requires additional information. Geoscience Australia describes land cover as:

'... the observed biophysical cover on the Earth’s surface including trees, shrubs, grasses, soils, exposed rocks and water bodies, as well as anthropogenic elements such as plantations, crops and built environments. Land cover changes for many reasons, including seasonal weather, severe weather events such as cyclones, floods and fires, and human activities such as mining, agriculture and urbanisation' (About Land Cover, Geoscience Australia website).

The ABS has produced land accounts for the GBR Region using the SEEA framework (Land Account: Great Barrier Reef Region, Experimental Estimates (cat. no. 4609.0.55.001)), although the Cape York NRM Region was excluded from those accounts. Table 3.1 below presents data on the opening and closing stocks of land cover in the GBR Region, including net changes.

	Opening Stock	Total Net Change	Closing Stock
Dynamic Land Cover	2008-09	2008-09 to 2010-11	2010-11
Built-up Surface (a)	57 700	0	57 700
Extraction Sites (a)	81 100	0	81 100
Bare Areas	500	0	500
Inland Waterbodies	153 400	2 700	156 100
Salt Lakes	500	-100	400
Irrigated Cropping	109 500	9 800	119 300
Irrigated Pasture	155 600	30 000	185 600
Irrigated Sugar (a)	189 300	0	189 300
Rainfed Cropping	774 500	-149 400	625 100
Rainfed Pasture	1 631 000	230 200	1 861 200
Rainfed Sugar (a)	47 800	0	47 800
Sedges - Open	0	0	0
Alpine Grasses - Open	0	0	0
Hummock Grasses - Closed	35 300	-9 700	25 600
Hummock Grasses - Open	11 100	-1 500	9 600
Tussock Grasses - Closed	8 504 700	-141 700	8 363 300
Tussock Grasses - Open	1 688 600	-905 200	783 400
Shrubs - Closed	46 900	-23 200	23 700
Trees - Closed	5 738 300	1 100 600	6 838 900
Trees - Open	9 852 700	3 548 300	13 401 000
Trees - Sparse	12 382 800	-3 383 400	8 999 400
Trees - Scattered	766 300	-398 800	367 500
Wetlands	314 700	105 600	420 300
Shrubs - Open	34 800	6 400	41 200
Shrubs and grasses - Sparse to scattered	163 300	-20 600	142 700
Total GBR Region	42 740 400	0	42 740 400
(a) Built-up Surface, Extraction Sites, Irrigated Sugar and Rainfed Sugar are static land cover types. These classes show no change over time.
Source: Dynamic Land Cover Dataset, Version 2 (DLCD V2), Geoscience Australia.

In 2008-09, Trees-Sparse accounted for 12.4 million hectares of all land cover in the GBR Region. Trees-Open is the second largest type of dynamic land cover at 9.9 million hectares, followed by Tussock Grasses-Closed at 8.5 million hectares. Trees-Sparse reported a net decrease of 3.4 million hectares between 2008-09 and 2010-11, from a total of 12.4 to nine million hectares. This was the largest decrease of any land cover type in the GBR Region. The change was driven by an increase of 3.5 million hectares in the Trees-Open category, making it the most abundant type of land cover in 2010-11.


RIVER LOAD

Suspended solids, nitrogen, phosphorous and photosystem II (PSII) inhibiting herbicides have all been shown to effect negatively the quality of marine environments and represent important indicators on the influence of land based activities on the downstream marine environment. Suspended solids, nitrogen and phosphorous are all naturally occurring river loads, although PSII inhibiting herbicides are of anthropogenic origin. The yield condition provides 'natural state' or ideal reference condition context to the load numbers reported in the tables below.

This section presents load data for indicative river systems for the GBR Region, and as yields of load per square kilometre of catchment compared to a reference condition by NRM Region over the period 2006-07 to 2011-12. Tables 3.2 and 3.3 below provide annual estimates for three types of annual loads: total suspended solids (TSS); total nitrogen (TN); and total phosphorous (TP). Table 3 also provides estimates of PSII inhibiting herbicides (pesticides) for the last two years of the time series; namely, 2010-11 and 2011-12.

			2006-07	2007-08	2008-09	2009-10	2010-11	2011-12
NRM Region	Load Type	Weight
Burdekin	TSS	'000 tonnes	6 503	12 700	9 614	1 937	6 200	3 300
	TN	tonnes	9 724	32 816	23 283	6 411	21 000	11 000
	TP	tonnes	3 240	9 179	6 721	2 213	8 400	3 400
	Pesticides	tonnes	na	na	na	na	882	642
Burnett Mary	TSS	'000 tonnes	na	na	na	146	2 600	15
	TN	tonnes	na	na	na	1 262	16 000	400
	TP	tonnes	na	na	na	330	3 800	47
	Pesticides	tonnes	na	na	na	na	448	29
Cape York	TSS	'000 tonnes	59	211	104	173	207	46
	TN	tonnes	711	1 814	1 098	1 326	5 600	490
	TP	tonnes	84	168	98	159	320	87
	Pesticides	tonnes	na	na	na	na	na	na
Fitzroy	TSS	'000 tonnes	320	4 751	404	3 563	7 000	1 300
	TN	tonnes	1 178	15 197	2 016	12 989	36 000	6 400
	TP	tonnes	403	5 671	657	5 321	15 000	2 700
	Pesticides	tonnes	na	na	na	na	8 557	1 956
Mackay Whitsunday	TSS	'000 tonnes	156	255	111	374	820	210
	TN	tonnes	927	1 378	849	1 929	4 100	1 300
	TP	tonnes	181	326	134	488	1 000	300
	Pesticides	tonnes	na	na	na	na	1 254	397
Wet Tropics	TSS	'000 tonnes	615	866	2 405	693	2 820	661
	TN	tonnes	5 791	6 306	9 637	5 417	18 300	7 880
	TP	tonnes	820	882	1 560	839	3 430	1 077
	Pesticides	tonnes	na	na	na	na	796	780
Total GBR Region	TSS	'000 tonnes	7 653	18 783	12 638	6 886	19 647	5 532
	TN	tonnes	18 331	57 511	36 883	29 334	101 000	27 470
	TP	tonnes	4 728	16 226	9 170	9 350	31 950	7 611
	Pesticides	tonnes	na	na	na	na	11 937	3 804
na - not available
TSS - Total Suspended Solids; TN - Total Nitrogen; TP - Total Phosphorous
Note: Data for the period 2006-07 to 2008-09 for the Burnett Mary NRM Region is not presented because no high flow events were recorded.
Sources: See the complete list at the end of this section.

Table 3.2 above shows that the total amount of river loads varies significantly between consecutive years in the majority of NRM Regions. A key reason for this volatility is the effect of rainfall and subsequent volume of river flow. For example, the 2010-11 flood events in Queensland increased river loads across all NRM Regions. There was a threefold increase in total suspended solids between 2009-10 and 2010-11 for the total GBR Region, and an even larger increase in total nitrogen and total phosphates in the same period. Loads, however, returned to pre-flood levels by 2011-12 in most regions.

The yield for each selected river basin was compared to the estimated pre-European yield in order to measure loads in the context of condition (see Kroon et al.,2012). It is an example of a reference condition not based upon accounting period considerations, but upon the notion of 'a condition reflecting an ecosystem which is relatively undisturbed or undegraded by humans' (SEEA Experimental Ecosystem Accounting, 2012, para. 4.16). This type of measure relates more to the condition of the landscape, its use and its ability to stabilise mass (or mitigate erosion), than to the physical form of the rivers. The resultant data shows how much the landscape has been functionally changed in this respect since European settlement.

The measure remains greatly influenced by rainfall and volume of river flow, but the size of catchment controlled as yield is measured in kilograms, or tonnes per square kilometre of catchment. Table 3.3 below presents yields of total suspended solids, total nitrogen and total phosphorous indexed to the pre-European reference condition. There were no pesticides present before European settlement, and, therefore, it is not possible to construct an index for this measure.

		Pre-European settlement condition	2006-07	2007-08	2008-09	2009-10	2010-11	2011-12
NRM Region	Load type
Burdekin	TSS	100	1 250	2 450	1 850	375	1 175	625
	TN	100	441	1 488	1 053	288	1 000	476
	TP	100	1 250	3 550	2 600	850	3 250	1 300
Burnett Mary	TSS	100	na	na	na	133	2 600	15
	TN	100	na	na	na	317	4 083	100
	TP	100	na	na	na	600	11 000	140
Cape York	TSS	100	71	229	114	186	300	51
	TN	100	117	298	181	219	915	81
	TP	100	120	260	160	240	500	134
Fitzroy	TSS	100	25	425	38	325	625	119
	TN	100	1 011	89	1 211	1 033	2 889	511
	TP	100	2 500	300	4 100	3 800	11 000	1 900
Mackay Whitsunday	TSS	100	176	413	177	472	949	303
	TN	100	236	525	517	953	1 742	625
	TP	100	320	877	348	1 425	2 636	1 205
Wet Tropics	TSS	100	476	638	1 717	434	1 727	413
	TN	100	350	370	549	264	870	375
	TP	100	466	494	838	353	1 427	413
na - not available
TSS - Total Suspended Solids, TN - Total Nitrogen, TP - Total Phosphorous
Note: Data for the period 2006-07 to 2008-09 for the Burnett Mary NRM Region are not presented because no high flow events were recorded. Yields for the Total GBR Region have not been derived. Yields for the Wet Tropics NRM Region are weighted by basin size for aggregate NRM yield.
Sources: See the complete list at the end of this section.

Table 3.3 above shows that there is considerable variance in the condition of selected rivers in the GBR Region. The selected river basin yields in the Cape York and Burnett Mary NRM Regions are closer to the reference condition in 2011-12 than other regions. There is a decrease of 49 per cent in the Cape York NRM Region in yield of total suspended solids relative to pre-European yields, and a decrease of 85 per cent in the Burnett Mary NRM Region of the same yield. In 2010-11, all yields were significantly increased by very heavy rainfall (including total suspended solids), to 300 per cent of the pre-European yield in the Cape York NRM Region, and by 2,600 per cent in the Burnett Mary NRM Region.

Increases in yield have been observed for the majority of measures each year in areas between the Cape York and Burnett Mary NRM Regions. The Fitzroy and Burnett Mary NRM Regions recorded the highest index value of all measures in 2010-11 (11,000), when both regions recorded a total phosphorous yield 110 times the pre-European condition. Total phosphorous in the Fitzroy NRM Region recorded the highest index value in 2011-12, with a yield nineteen times (1,900) that of the pre-European condition (100).


NET PRIMARY PRODUCTIVITY

Net primary productivity (NPP) is defined as the net flux of carbon from the atmosphere into green plants per unit time. It is a fundamental ecological variable. It not only measures the energy input into the biosphere and terrestrial carbon dioxide assimilation, but also indicates the condition of the land surface area and the status of a wide range of ecological processes.

NPP is used in this information paper as an indicator for the 'vegetation' characteristic of terrestrial condition. The term 'net' refers to the balance (over time) between the rate of gain of carbon in leaves, stems, and roots by photosynthesis (known as gross primary productivity or GPP) and the rate of loss of biomass via respiration. It is positive in cases where the photosynthetic rate exceeds the respiration rate and negative where the respiration rate exceeds the photosynthetic rate.

The NPP estimates reported in this release are produced from the BIOS2 model developed by the CSIRO.

NPP is also applicable to marine areas, but an analysis of those areas has not been undertaken as part of this release. There are a range of possible derivation methods for estimating changes in area of seagrass, coral and mangrove but the required time series data are not available. Chlorophyll concentration is used in some derivation methods to measure marine NPP, and is included in the water quality indicator in the Seascape section.

Table 3.4 below shows the total amount of NPP in kilotonnes of carbon for each NRM Region for the period, 2000-01 to 2012-13.

	2000-01	2001-02	2002-03	2003-04	2004-05	2005-06	2006-07	2007-08	2008-09	2009-10	2010-11	2011-12	2012-13
NRM Region
Burdekin	85 772	58 077	45 586	54 192	42 497	61 798	62 061	91 428	90 418	81 657	112 380	86 321	73 885
Burnett Mary	38 156	33 316	40 161	44 690	35 665	38 610	27 663	44 885	43 684	41 897	56 600	47 960	45 956
Cape York	30 095	29 676	24 588	26 563	27 223	26 772	31 070	29 705	31 088	26 534	33 334	29 782	29 469
Fitzroy	104 600	74 061	83 255	86 524	72 011	84 707	67 191	124 477	112 166	112 639	158 341	117 765	108 137
Mackay Whitsunday	10 593	9 401	7 826	8 895	7 913	8 782	9 241	10 468	9 514	9 346	9 888	10 247	9 802
Wet Tropics	22 722	23 118	20 628	20 693	21 387	20 938	23 079	23 626	23 994	21 826	22 776	22 317	22 421
Total GBR Region	291 939	227 647	222 043	241 557	206 696	241 608	220 304	324 588	310 865	293 899	393 321	314 392	289 670
Source: Haverd et al.,2013b

The GBR Region recorded a small decrease from 291,939 kilotonnes to 289,670 kilotonnes (or 0.8 per cent) between 2000-01 and 2012-13. Variation across years is very large, with a low of 206,696 kilotonnes in 2004-05 (a drought year), and a high of 393,321 kilotonnes in 2010-11 (a high rainfall year).

The Cape York NRM Region recorded a 2.1 per cent decrease over the period, 2000-01 to 2012-13; the Wet Tropics NRM Region recorded a smaller decrease of 1.3 per cent. The Burdekin NRM Region recorded the largest decrease both in percentage and absolute terms, by assimilating 11,888 kilotonnes less in 2012-13 than in 2000-01 (or 13.9 per cent).

Figure 3.1 below highlights the impact of variable rainfall. This map shows the differences in net primary productivity across the terrestrial area of the GBR Region between the very dry year, 2002-03 and the very wet year, 2010-11. The coastal area of Burdekin NRM Region and the inland area of Fitzroy NRM Region show some of the greatest variations in NPP between the two years.




The indicator used to measure vegetation condition is mean grams of carbon assimilated per square metre per day (g C/ m² / day). Table 3.5 below shows the index values for each NRM Region in the GBR Region.

	2000-01	2000-01	2001-02	2002-03	2003-04	2004-05	2005-06	2006-07	2007-08	2008-09	2009-10	2010-11	2011-12
NRM Region	g C/m2/day	points	points	points	points	points	points	points	points	points	points	points	points
Burdekin	1.70	100	68	53	63	50	72	73	106	106	95	131	100
Burnett Mary	1.90	100	87	105	116	93	101	72	117	114	110	148	125
Cape York	2.12	100	99	82	88	91	90	103	99	104	88	111	99
Fitzroy	1.84	100	71	80	82	69	81	64	119	107	108	151	112
Mackay Whitsunday	3.59	100	89	74	84	75	83	87	99	90	88	93	97
Wet Tropics	3.11	100	102	91	91	95	93	102	104	106	96	100	98
Total GBR Region	2.38	100	88	81	88	80	87	86	106	103	96	117	103
g C/m2/day — grams of carbon per cubic metre per day
Source: Haverd et al., 2013b

There are large differences between NRM Regions in terms of the amount of carbon assimilated per square metre. For example, the Mackay Whitsunday NRM Region assimilated more than twice the carbon per square metre than the Burdekin NRM Region in 2000-01. On the one hand, the vegetation condition of the Burnett Mary NRM Region has improved by 25 per cent over the reference period, and the Fitzroy NRM Region by 12 per cent. On the other hand, the condition of the Mackay Whitsunday NRM Region decreased by three per cent in the same period.


LIST OF REFERENCES

CSIRO (2014) Assessment of freshwater ecosystem condition, status and trends in the Wet Tropics region. Supporting study to the Wet Tropics Water Quality Improvement Plan. Canberra: Commonwealth Scientific and Industrial Research Organisation (CSIRO).

DSITIA (2013) Total suspended solids, nutrient and pesticide loads (2010-2011) for rivers that discharge to the Great Barrier Reef Great Barrier Reef Catchment Loads Monitoring 2010-2011. Brisbane: Queensland Department of Science, Information Technology, Innovation and the Arts (DSITIA).

Haverd, V. et al. (2013a) 'Multiple observation types reduce uncertainty in Australia’s terrestrial carbon and water cycles', Biogeosciences, Vol. 10, No. 3 (March), pp.2011–2040.

Haverd, V. et al. (2013b) 'The Australian terrestrial carbon budget', Biogeosciences, Vol. 10, No. 3 (February), pp.851–869.

Joo, M. et al. (2012) 'Estimates of sediment and nutrient loads in 10 major catchments draining to the Great Barrier Reef during 2006–2009', Marine Pollution Bulletin, Number 65, pp.150-166.

Kroon, F.J. et al. (2012) 'River loads of suspended solids, nitrogen, phosphorus and herbicides delivered to the Great Barrier Reef lagoon', Marine Pollution Bulletin, Number 65, pp.167-181.

Turner, R. et al. (2012) Sediment, Nutrient and Pesticide Loads: Great Barrier Reef Catchment Loads Monitoring 2009-2010. Brisbane: Queensland Department of Science, Information Technology, Innovation and the Arts.

Wallace, R. et al. (2014) Total suspended solids, nutrient and pesticide loads (2011–2012) for rivers that discharge to the Great Barrier Reef – Great Barrier Reef Catchment Loads Monitoring Program 2011–2012. Brisbane: Queensland Department of Science, Information Technology, Innovation and the Arts.